basic concepts of hematology (hemostasis)

8/9/2019 Basic Concepts of Hematology (Hemostasis)

1/53

BASIC CONCEPTS OF HEMATOLOGY

Hemostasis

Objectives are indicated by number. The student upon completion of the

classroom component of the hemostasis section will be responsible tosuccessfully:

01 EXPLAIN THE BASIC CONCEPTS / PURPOSES OF HEMOSTASIS.

Hemostasis (hemo = blood + stasis = stop, cease) is a process by which the bodymaintains the life flow of blood and prevents bleedin problems. Hemostasis isa comple! se"uence of interactions in the (1) blood vessels, (2) thrombocytes,(3) coa ulation proteins of blood, and (4) fibrinolytic proteins of blood. Thismechanism is able to retain blood within the injured vessel until the repair iscompleted. The end product of hemostasis is the transformation of blood into a

thrombus or clot. This is the culmination of a three step phenomenonconsistin of (1) e!travascular, (2) vascular, and (3) intravascular phases.

02 LIST FIVE FACTORS WHICH AFFECT THE EFFECTIVENESS ORINEFFECTIVENESS OF HEMOSTASIS.

1! Type of injury, bruise, cut, abrasion, etc.2! #a nitude of the injury.3! $i%e of the vessels involved and their ability to respond.4! Hydrostatic pressures within the blood vessels and tissues."! &vailability, "uantity, and "uality of platelets, clottin factors, andinhibitors.

03 DESCRIBE AND/OR ILLUSTRATE THE THROMBOCYTE .

The thrombocyte (platelet) is an active 'sol el structure capable ofunder oin rapid morpholo ical chan es. The platelet consists of four distinct%ones (*) peripheral %one, (+) 'sol el %one, ( ) or anelle %one, and - /membrane %one. 0ach %one has a uni"ue function to be covered in thefollowin objectives. 1eview the followin illustration which displays a crosssection of a platelet.


2/53

04 DISCUSS THE PERIPHERAL ZONE AND ITS FUNCTIONAL ROLE IN THEPLATELET.

The peripheral %one consists of the e!terior coat or lycocaly!, plateletmembrane, surface connectin channels (open canalicular system), andsubmembranous re ion. The lycocaly! contains a variety of lycoproteins thatconstitute the &2O anti ens and human leu3ocyte anti ens (H4&). Thelycoproteins function as receptors and stimuli transmitters across the plateletmembrane. The platelet membrane is also made up of lipoproteins,phospholipids, and lycolipids. These molecules function as receptors for (1) fibrino en, (2) fibronectin, (3) von5illebrand 6actor, (4) epinephrine (") thrombin, (#) &78, and ($) serotonin. 8latelet factors 86* 869 alon withcoa ulation factors and ;;; are found on the platelet membrane. The opencanicular system serves as a means for releasin platelet stored products to theoutside.A. The


3/53

/% G 'o-&otei* I/+ a &e'e-to& mo e' e .o& o* i e/&a* 5s .a'to&%'% G 'o-&otei* IIa6IIIa 'om- e7+ a &e'e-to& .o& 8/&i*o9e*%% P os- o i-i s (- os- ati ' o i*e+ - os- ati et a*o ami*e+- os- ati i*osito + a* s- i*9om e i*)

0" DISCUSS THE GEL-SOL ZONE AND ITS FUNCTION IN THE PLATELET.

This mid %one structure forms the cytos3eleton of the platelet. ;t may bereferred to as the structural %one and contains a matri! of microtubules,microfilaments, and submembranous filaments. The submembranous filamentse!tend into the peripheral %one.A. The microtubules are found throu hout the platelet and help to conform toit discoid shape. The microtubules have contractile capability and can causemovement of the or anelles to facilitate platelet secretion activity. Thecontractile ability of the microtubule enable the tubules to concentrate invarious re ions of the platelet. These structures re ulate secretion responses of

the platelet in addition to its 's3eletal role.B. The microfilaments are composed of thrombosthenin, actin, and myosinfilaments. These contractile proteins ma3e up the major portion of the plateletproteins. They are found throu hout the interior of the platelet. They e!ist inan unor ani%ed elatinous state and upon proper stimulus they will or ani%einto a definite structure to cause platelet contraction.C. $ubmembranous filaments are speciali%ed microfilaments that lin3 the outerplatelet membrane to the microfilaments in the 'sol el area. These mayfacilitate or ani%in the platelet>s shape and to affect the ranules.The primary function of the 'sol el %one is to provide a cytos3eleton for theplatelet and enable it to contract to release platelet secretions and enable the

formation of the pseudopods involved in the coa ulation process.

0# DISCUSS THE ORGANELLE ZONE AND EXPLAIN ITS FUNCTION .

The metabolic activities of the platelets are carried out in this innermost %one.The major structures in the or anelle %one are (1) dense ranules, (2) alpharanules, (3) pero!isomes, (4) mitochondria, (") lyco en, and (#) lysosomes.A. &lpha ranules in a sin le platelet ran e form +? to +?? in number. Theseranules contain a wide assortment of molecules: (1) platelet factors * 9, (2) @ thrombo lobulin, (3) basic protein, (4) platelet derived rowth factor, (") fibrino en, (#) v56, ($) factor , (:) albumin, (;) fibronectin, (10)

plasmino en, (11) hi h molecular wei ht 3inino en, (12) protein $, (13) ;


4/53

C. 4ysosomes contain acid hydrolases.D. #itochondria are ener y production or anelles, numberin from *? to Aper platelet. 8latelets re"uire ener y to function in hemostasis. 8latelet &T8 isenerated by lycolysis and the Breb>s cycle.

0$ DESCRIBE THE MEMBRANE SYSTEM OF THE PLATELET.This is a structural %one that consists of a dense tubular system and an opencanicular system (OC$) that connect the outer surface of the platelet to itsinner re ions. These two tubular systems can fuse to form a membranecomple!. The principle role is associated with calcium ions (stora e andrelease).

0: DESCRIBE HOW PLATELET ACTIVATION IS INITIATED .

&ctivation can be either transient, reversible, or irreversible. 8latelet

activation causes the platelet to respond in a raded fashion that includesstic3iness, adhesion, shape chan es, release of platelet substances, anda re ation. The stren th and duration of the stimulus determines the plateletresponse. &nother factor that affects the platelets activation is thephysiolo ical health of the platelet. 5hen the platelet is activated, pseudopodswill form, and the platelet be ins to contract. 6actors that will cause plateletactivation are (1) e!posure to colla en from vascular injury, (2) &78, (3)platelet activatin factor, (4) thrombin, (") epinephrine, (#) thrombo!ane &.

NOTE1! T &om/o7a*e A is a -&osta9 a* i* t at 'a* 'a se t e .o&matio* o.

t &om/i% It =2=a'et 9 'e&o- os- o=' o i*e%

3! T &om/i* is a'ti ate -&ot &om/i* a* is -a&t o. t e 'oa9 atio*s' eme%

4! E-i*e- &i*e is a o&mo*e >*o o


5/53

#! Co a9e* is a ma,o&


6/53

11 DISCUSS THE PRIMARY AGGREGATION PHASE OF PLATELET PLUGFORMATION

The attachment of platelets to each other is called a re ation. This

attachment phenomenon appears to occur in two sta es. The first or primarysta e is the loose con lomeration of platelets that occurs before the secretoryphase be ins. This primary sta e is unstable can be reversed if the stimulus iswea3 that initiated the adhesion process. ;f the a re ation phenomenon isintense and a ressive, the release of chemicals will initiate the secondaryphase, which is stable and cannot be reversed.

12 DISCUSS THE SECRETION PHASE OF PLATELET PLUG FORMATION .

This is also called the release reaction step. This phase may be in immediatelywith an intense adhesion phenomenon. There is a release phenomenon by the

dense bodiesD ranules in which serotonin, &78, and calcium are initiallyreleased. The Open Canalicular (OC$) be ins to move calcium ions to theoutside to increase the e!tracellular Ca EE levels. &lpha ranules also releasetheir substances. The secretion phase helps to convert the a re atinplatelets into a mass of de enerated platelets without membranes. Thistransformation phenomenon is called viscous metamorphosis. &78 binds withthe platelet receptors mobili%es the fibrino en bindin sites.

13 LIST SIX SECRETORY PRODUCTS RELEASED BY DENSE GRANULES OFPLATELETS AND IDENTIFY WHAT ROLE THEY HAVE IN THE CLOTTINGPROCESS.

1! Calcium: activates Ca EEsensitive phospholipases which drive reactions toform thrombo!ane &+ from arachidonic acid.2! &78: bind to platelet membrane receptors to activate fibrino en bindinsites.3! $erotonin: a vasoactive amine causin vascular constriction.4! 0pinephrine: an amine active vasoconstrictor."! &T8: ener y molecule to facilitate platelet activation.#! #a nesium: cofactor for &78 and &T8.

14 LIST SEVEN SECRETORY PRODUCTS RELEASED BY ALPHA GRANULES OF PLATELETS AND IDENTIFY THEIR ROLE IN THE CLOTTING PROCESS .

1! 6ibronectin: a protein with adhesive properties to bind platelets to eachother.2! Thrombospondin (T$8): a protein with adhesive properties to bindplatelets to each other.3! 6ibrino en: a clottin protein to form a brid e between platelets andendothelium.


7/53

4! 8latelet 7erived s in the platelet fibrin clot, and (") hardening of the fibrinpolymer by fibrin-stabilizing factor (G;;;).

The secondary a re ation step is also characteri%ed by additionalde ranulation within the platelets, releasin more substances to drive theplatelet plu process into it irreversible phase.

1# DESCRIBE HOW ASPIRIN AFFECTS PLATELET ACTIVITY.

1! ;t inhibits the production of platelet cyclo o!y enase, an en%yme that isre"uired for the production of prosta landins and thrombo!anes that havediverse functions that include vasoconstriction of blood vessels, plateleta re ation, and blood pressure re ulation.A % C ' o=o7 9e*ase (a so


8/53

4! ;f a patient is ta3in aspirin as a therapeutic preventative measure, theymust discontinue for ei ht days before reliable bleedin times can be obtained.

17 BRIEFLY DESCRIBE HOW CLOT RETRACTION OCCURS.

8latelets contain in their cytoplasm, structural proteins that include actin andmyosin. ;n clot retraction, calcium and &T8 stimulated actin and myosinmolecules contract to reduce the si%e of the plu and e!trude plasma. Thiscontraction phenomenon is dependent upon the presence of fibrino enreceptors ( lycoprotein ;;bD;;;a comple!) that are occupied by fibrino en,fibrin, or fibronectin. NOTE: If these receptors are missing from the platelet,the platelet(s) ill not contract! This condition is "no n as thrombasthenia!

1: GIVE ONE EXAMPLE OF HOW PLATELETS CONTRIBUTE TO THE FIBRIN-FORMING SYSTEM.

8latelets produce phospholipid platelet factor (86 ) at a hidden site on themembrane. 5hen this factor is e!posed, it becomes a catalytic molecule thatcan activate selected clottin factors such as factors ;G, G, and ;;.

1; EXPLAIN WHAT IS MEANT BY THE TERM, FIBRIN FORMING SYSTEM.

;t is the interaction of the protein clottin factors to form a fibrin clot whichwill help to stabili%e the platelet plu .

20 WHAT IS G-PROTEIN?

< protein (also called


9/53

22 EXPLAIN THE MEANING OF THE TERMS, PRIMARY HEMOSTASIS ANDSECONDARY HEMOSTASISL

8rimary hemostasis refers to the formation of the platelet plu . $econdary

hemostasis refers to the formation of the fibrin clot.23 LIST FOURTEEN COAGULATION FACTORS, COMMON NAMES,

ABBREVIATIONS AND/OR SYNONYMS.

factor common name ( ith "no n synonyms)I 6ibrino enII 8rothrombinIII Tissue ThromboplastinI Tissue 6actorI ;oni%ed Calcium (Ca EE)

8roaccelerin, 4abile 6actor, 8rothrombin &ccelerator, &ccelerator


10/53

activation of the intrinsic coa ulation pathway. They re"uire a ne ativelychar ed surface to activate. Only 6actor I appears to have an essential role inthe clottin scheme.

The four prothrombin types of coa ulation factors are prothrombin (II), stable

factor ( II ), $hristmas factor (I ), and %tuart-&ro er 'actor ( ). These arelow molecular wei ht factors and they re"uire vitamin B for synthesis. Thesefactors contain amma carbo!y lutamic acid that is necessary for bindincalcium ions. The carbo!y lutamic acid component (with the calcium ions)enables the molecule to be attracted to the acidic phospholipid surface of theplatelet to ta3e part in the clottin process. These factors can be precipitatedand removed by barium sulfate or aluminum hydro!ide. These factors areproduced in the liver. Other prothrombin type proteins 3nown to have an effectin coa ulation are protein C and protein $ ($ee Objective KA and Objective K9).NOTE: If itamin is absent, the clotting proteins are synthesized but ithoutthe functional carbo*yl groups to bind calcium! These proteins may be

referred to as &rotein Induced by +itamin absence antagonist (&I+ )!

The four fibrino en types of coa ulation factors are -*/ fibrinogen , (+) proaccelerin ( ), - / antihemophilic factor ( III ), and - / fibrin-stabilizing factor ( III ). These are present in normal and absorbed plasma. They are notfound in serum because they are consumed in the clottin process (formationof fibrin). 6actors and III are the least stable of the clottin factors becauseof their labile tendency to de radation and denaturation.

La/i e es'&i/es t e te* e*' to /e *sta/ e *stea + *ot 87e % It e*otes

1% A* a a-ta/i it to a te&atio* o& mo i8'atio*+ i%e%+ &e ati e easi ' a*9e o&&ea&&a*9e %2% Ce&tai* 'o*stit e*ts o. se& m aJe'te / i*'&eases i* eat%3% Easi &emo a/ e e%9%+ a a/i e &o9e*%

2" LIST THE COAGULATION FACTORS DESCRIBED AS SERINE PROTEASES

Ha eman factor (G;;) 8lasma Thromboplastin &ntecedent (G;)6letcher factor Christmas 6actor (;G)8rothrombin (;;) 8rotein C$table 6actor ( ;;)

NOTE$erine proteases re"uire an active serine molecule in the catalytic site. Thetar et site of serine proteases are specific peptide bonds in protein moleculesand in many cases their tar et molecule is another molecule containin serine.8rotein activation by these proteases tends to be limited to the hydrolysis ofone or two peptide bonds.


11/53

2# LIST THE NOWN CLOTTING FACTORS AND DESCRIBE THE FOLLOWINGFEATURES FOR EACH OF THE FACTORS! "#$ BLOOD CONCENTRATION, "%$HALF-LIFE IN HOURS, "&$ VITAMIN DEPENDENCY, "'$ COAGULATIONPROTEIN GROUP, "($ TYPE OF PROTEIN, ")$ SITE OF PRODUCTION, "*$CLOTTING PATHWAY INTERACTION, "+$ STORAGE , AND " $ BIOCHEMICAL

FUNCTION.

A% Fi/&i*o9e* (I)-*/ blood concentration +?? to ?? m Dd4-+/ half life, hours M? to *+? hours- / vitamin B dependency: not dependent- / coa ulation protein roup: fibrino en-K/ type of protein: lycoprotein-A/ site of production: liver-9/ clottin pathways: intrinsic, e!trinsic, and common-N/ stora e: stable

-M/ biochemical function: substrate

B% P&ot &om/i* (II)-*/ blood concentration: *? m Dd4-+/ half life, hours: A? hours to *?? hours- / vitamin B dependency: yes- / coa ulation protein roup: prothrombin-K/ type of protein: F+ lobulin-A/ site of production: liver-9/ clottin pathways: intrinsic, e!trinsic, and common-N/ stora e: stable

-M/ biochemical function: serine protease

C% Tiss e T &om/o- asti* (III)-*/ blood concentration: none-+/ half life, hours: not 3nown- / vitamin B dependency: no- / coa ulation protein roup: none-K/ type of protein: lipoprotein-A/ site of production: all tissues, it is hi hest in the brain, liver, lun ,placenta.-9/ clottin pathways: e!trinsic

-N/ stora e: stable-M/ biochemical function: cofactor

% Io*i e Ca 'i m (I )-*/ blood concentration: .N to .M+ m Dd4 (+.+ to +. A m0"D4)-+/ half life, hours: nor applicable- / vitamin B dependency: not dependent- / coa ulation protein roup: none


12/53

-K/ type of protein: not a protein-A/ site of production: absorbed across the intestinal wall-9/ clottin pathways: intrinsic, e!trinsic, common-N/ stora e: stable-M/ biochemical function: cofactor

;oni%ed calcium is different from total calcium which ma3es up N. to *?.+m Dd4. K is protein bound, K is ioni%ed, and *? is li and (lactate, citrate,phosphate, and bicarbonate) bound

E% P&oa''e e&i* ( ) -*/ blood concentration: K to *+ P Dm4-+/ half life, hours: *+ to A- / vitamin B dependency: not dependent- / coa ulation protein roup: fibrino en-K/ type of protein: lycoprotein

-A/ site of production: liver-9/ clottin pathways: intrinsic, e!trinsic, common-N/ stora e: labile-M/ biochemical function: cofactor

F% P&o'o* e&ti* ( II)-*/ blood concentration: *? to *+ P Dm4-+/ half life, hours: K to N hours- / vitamin B dependency: yes- / coa ulation protein roup: prothrombin-K/ type of protein: lycoprotein

-A/ site of production: liver-9/ clottin pathways: e!trinsic-N/ stora e: stable-M/ biochemical function: serine protease

G% A*ti emo- i i' Fa'to& ( III)-*/ blood concentration: *? to +? P Dm4-+/ half life, hours: N to *+- / vitamin B dependency: not dependent- / coa ulation protein roup: fibrino en-K/ type of protein: multi protein comple!

-A/ site of production: liver-9/ clottin pathways: intrinsic-N/ stora e: labile-M/ biochemical function: cofactor

H% C &istmas Fa'to& (I )-*/ blood concentration: to P Dm4-+/ half life, hours: +? to 9+


13/53

- / vitamin B dependency: yes- / coa ulation protein roup: prothrombin-K/ type of protein: dipeptide chain lin3ed by disulfide bonds-A/ site of production: liver-9/ clottin pathways: intrinsic

-N/ stora e: stable-M/ biochemical function: serine protease

I% St a&t=P&o


14/53

-K/ type of protein: double chain F+ lobulin-A/ site of production: liver-9/ clottin pathways: intrinsic, e!trinsic, common-N/ stora e: stable-M/ biochemical function: serine protease

M% F et' e& Fa'to&-*/ blood concentration: K to K? P Dm4-+/ half life, hours: appro!imately K- / vitamin B dependency: not dependent- / coa ulation protein roup: contact-K/ type of protein: amma lobulin-A/ site of production: liver-9/ clottin pathways: intrinsic-N/ stora e: stable-M/ biochemical function: serine protease

N% Fit 9e&a Fa'to&-*/ blood concentration: 9? to M? P Dm4-+/ half life, hours: appro!imately *KA- / vitamin B dependency: not dependent- / coa ulation protein roup: contact-K/ type of protein: lycoprotein-A/ site of production: liver-9/ clottin pathways: intrinsic-N/ stora e: stable-M/ biochemical function: cofactor

NOTE T# T ON./ '$TO0% + N1 +III 0E . 2I.E!

2$ DISCUSS AND / OR ILLUSTRATE THE EXTRINSIC COAGULATION PATHWAY.

The e!trinsic coa ulation pathway is an alternate pathway describin how6actor G can be activated and re"uires 6actor ;;; (tissue thromboplastin). Thispathway is initiated e!ternal to the vascular system. Tissue thromboplastin islocated outside the vascular system and is a membrane protein. 5hen tissuetrauma occurs, it is released and be ins the cascade process. 8roconvertin ( ;;)is uni"ue to this system and will bind with tissue thromboplastin in the

presence of calcium . The e!trinsic cascade coa ulation se"uence is as follows:

2: DISCUSS AND / OR ILLUSTRATE THE INTRINSIC COAGULATION PATHWAY.


15/53


16/53

2; EXPLAIN THE TENASE COMPLEX IN THE COAGULATION PATHWAY.This is a reaction step that occurs on the platelet membrane as a part of theintrinsic pathway. ;t is the formation of an en%yme comple! between 6actor ;Gand ;;;:C, CaEE, and platelet factor (86 ). This en%yme comple!, as it sits onthe platelet membrane will activate 6actor G. The comple! is called the tenasecomple* because of the conversion of the inactive factor G to its active form.The surface of the platelet provides a protective environment for thecoa ulation reactions from the interferences of opposin molecules.

30 ILLUSTRATE HOW THE VARIOUS COAGULATION PATHWAYS INTERACT .

1efer to the ne!t three pa es desi nated as Coa ulation 8athways. These pa esmay be attached to form a three pa e fold out.


17/53


18/53


19/53

31 DISCUSS THE COMPLEX NATURE OF COAGULATION FACTOR VIII .

6actor ;;; is a comple! of several components and constitutes the lar estmolecule in the coa ulation scheme. The two principle subunits of 6actor ;;;are:1! $ubunit ;, which is a procoa ulant and may be written as ;;;:C.&. This part of the molecule is the antihemophilic factor.


20/53

2. Certain receptors of ;;;:C bind to CaEE and then bindin to the plateletoccurs.C. The coa ulant properties are in this subunit.2! $ubunit ;;, which is that portion of factor ;;; that bonds with von5illebrand 6actor (v56) and may be desi nated as the ;;; v56 comple!. The

comple! forms the functional molecule.3! 2oth subunits ; and ;; form the basic molecule. The acronym ;;;&desi nates that part of the basic molecule that is anti enic.

6actor ;;;:C production occurs primarily in the hepatocytes and is controlledby enes in the G chromosome. ;t is somewhat unstable and has a short half life(N to *+ hours). 5hen it comple!es with v56, it increases it stability severalfold. ;t is this portion of 6actor ;;; that is under produced or not at all inhemophilia. 0ach part of factor ;;; has its own biolo ical and immunolo icalproperties. Qote that some of 6actor ;;; circulates free but will not befunctional.

32 DISCUSS WILLEBRAND FACTOR 0 WF1 AND ITS ROLE INCOAGULATION .

v56 is a lycoprotein and is thou ht to be synthesi%ed in the endoplasmicreticulum of endothelial cells (the 5eibel 8alade bodies) and me a3aryocytes.This factor is released and absorbed onto the surface of platelets and stored inthe alpha ranules of the platelet. ;t is also absorbed onto the endotheliallinin of the vascular system, where it is stored in ranules called 5eibel8alade bodies. v56 is a comple! molecule, associated with factor ;;;. ;t isdescribed as a lar e, adhesive multimeric lycoprotein with a molecular wei ht

(7altons) from A??,??? to +? G *?A

. v56 e!ists in several entities. The lowmolecular wei ht form (++?,??? 7altons) is a monomer. ;t has capability toform a type of polymer composed of a variable number of subunits (dimers,trimers, tetramers, and multimers), ivin rise to the hi her molecular wei htmolecules which supports v56 activity. 5hen injury occurs and plateletactivation be ins, the v56 that is bound to the platelet>s lycoprotein ;b andlycoprotein ;;bD;;;a receptors, will bind by another receptor site to thee!posed endothelial colla en andDor heparin, formin a brid e. v56 isessential for the platelet to adhere to the colla en fibers. The v56 subunitcontains (1) anti enic determinants, (2) ristocetin receptors, and (3) colla enDplatelet receptors. Note A -&o o*9e / ee i*9 time ma

i* i'ate a F e8'ie*' as 'a* a* a/*o&ma APTT a* &isto'eti*- ate et a99&e9atio* test% T is 'a* /e s /sta*tiate / a F assa%

&cronyms used with the v56 are as follows:v56 refers to the basic molecule re ardless of whether it is a dimer, trimer ormultimer.v56:& (called von 5illebrand>s anti en) is the anti enic portion of the basicmolecule without re ard to its molecular wei ht and ability to function. ;t as


21/53

been recommended that this acronym be discontinued or interpreted withcaution.v56:Co represents the reactive portion of the basic molecule.

The followin facts pertain to the v56 molecule:

1! v56 ma3es up M? of the ;;;:v56 comple!2! v56 appears to have no coa ulant properties, but acts as a stabili%er forfactor ;;;.3! v56 ives factor ;;; distinctive anti enic characteristics.4! v56 provides factor ;;; with the bindin sites to attach to the plateletand injury site. The lar e si%e of this comple! enable bindin the platelet tothe site of injury."!


22/53


23/53

A. *?? KN = + and KMK KN = K 9 therefore + divided by K 9 = ?.?9N+B. multiply ?.?9N+ times .K (m4s of blood to be collected) = . K+ m4s.C. 8lace ?. K of .*?M # sodium citrate in a test tube and add .K m4s patient>sblood.

Qomo rams are available to calculate the amount of anticoa ulant re"uired tomaintain a *:*? anticoa ulant ratio in the blood. 1efer to the followin raphas an e!ample.

3# LIST FIVE STEPS FOR HANDLING THE PATIENT4S SPECIMEN AFTERCOLLECTION FOR COAGULATION TESTING .

STEP 1 : &fter returnin to the laboratory and before and after centrifu ation,

e!amine the specimen for clots. NOTE B oo is 'e*t&i. 9e


24/53

formation, collect the specimen "uic3ly via a flawless venipuncture and mi!the tube of blood ently but thorou hly and immediately after collectin .

STEP 2 : Complete the coa ulation testin within ? minutes to + hours. NOTESome -&o'e &es ma /e -e&.o&me


25/53

3: DISCUSS THE TESTING STRATEGY FOR DETERMINING THE END POINTOF COAGULATION .

#ost tests are desi ned to detect the time re"uired for the formation of afibrin clot. $ome tests may consist of combinin calcium, thromboplastin (with

or without an activator) and citrated plasma. The fibrin clot can be detectedeither visually, electro mechanically, or by chan e in the optical density.

Ori inally the tilt tube or loop method were employed to detect the clot. Thetilt tube re"uired continuous tiltin of the tube bac3 and forth until the formedclot became visible. The loop method re"uired the use of a wire that waspassed throu h the mi!ture (about two sweeps per second) until a clotattached to the wire. The ne!t step in the evolution of clot detection utili%ed aset of electrodes that would be submer ed in the reaction mi!ture and sweepbac3 and forth until a clot formed. The developed clot forms an electricalcircuit that will stop the timer. The ne!t eneration of automated coa ulation

devices uses optical density (spectrophotometry). ;n this case the formation ofthe fibrin clot causes a chan e in the optical density of the plasma, alsoresultin in the stoppin the timer.

3; DESCRIBE IN SIMPLE TERMS THE PROTHROMBIN TIME PROCEDURE .

The prothrombin time (8T) re"uires 1 ! the placement of a desi nated amountof thromboplastin rea ent in the reaction well or tube, 2 ! allowin the plasmatemperature to adjust to 9 oC, and 3 ! add a desi nated amount of citratedplatelet poor plasma (888). 5hen all rea ents have been added allow mi!into ta3e place and record the time that the fibrin clot forms. & normal 8T test

will be in the ran e of *? to * seconds.

40 BRIEFLY DESCRIBE HOW TO EVALUATE A PROTHROMBIN TIME TEST .

;f the time e!tends + seconds beyond the normal ran e, this may indicate aproblem. ;f the prothrombin time (8T) procedure is performed in duplicate, thesecond test must be within *? of the first test. ;f factors is ;G, ;;, andDor Gare +? to AK of normal, the 8T many be prolon ed by * to seconds. The 8Tis prolon ed when factor ;; is *? of normal and fibrino en is *?? m Dd4. ;fthe 8T patient>s test result is three times that of normal, the patient is at ris3for hemorrha e and the physician may administer an antidote. ;f a coa ulationscheme is reviewed, it would indicate that the 8T test would be prolon ed ifthere was a deficiency in factors ;, ;;, , ;;, ;;;, ;G, and G. ;n reality the 8Ttest is most sensitive to a factor ;; deficiency and moderately sensitive todeficiencies in factors and G. ;t is sensitive to a mar3ed deficiency in either6actor ; and ;;. ;t is totally insensitive to deficiencies in factors ;;; and ;G.

NOTE


26/53

The plasma ali"uot must be incubated for at least three minutes, but no lon erthan ten minutes. 6actors and ;;; are labile and will deteriorate after tenminutes of incubation time. 0vaporation also occurs, which affects the "ualityof the test. 4on incubation times results in evaporation or rea ents andadversely affects the 8T. The net effect is that the 8T will be falsely prolon ed.

5hen settin up reference intervals, one laboratory may establish a normalcontrol ran e of *+ to * seconds and another laboratory use ** to * secondsas its normal ran e. 1eference ran es can be affected by the patientpopulation, type of thromboplastin, type of instrumentation, and the pH andpurity of the distilled water. 0ach laboratory should establish its own normalran e annually usin a minimum of +? healthy individuals of both se!es.

41 DISCUSS AND/OR CALCULATE THE INTERNATIONAL NORMALIZED RATIO0INR1.

The ;nternational Qormali%ed 1atio (;Q1) is an attempt to standardi%e thethromboplastin rea ents of the different rea ent manufacturers to that of theinternational reference thromboplastin -5orld Health Or ani%ation (5HO)human brain thromboplastin/. This process has developed because differentthromboplastins do not have the same sensitivity. #anufacturers calibrate eachlot of their 8T thromboplastin a ainst the standard 5HO thromboplastinrea ent. The rea ent manufacturers will then calculate an internationalsensitivity inde! (;$;) number for their rea ent. This ;$; number can be enteredinto the automated coa ulation instrument and a corrected calculation can bemade for each patient. 8ro rammable hand held calculators can formulate the;Q1 if the ;$; is entered. #anufacturers provide tables for their rea ents andthe 8T ratio and ;$; can be loo3ed up and reported. The ;Q1 is the patient>sprothrombin time ratio to the power e"ual to the ;$;. The followin formulashows how to calculate the ;Q1. ;Q1 = (8T patient D 8Tnormal );$;

The followin problem is provided as an e!ample. &ssume that the patient>s 8Tis *A seconds, the normal control is *+ seconds, and the ;$; = +.?. The problemwill set up as follows:;Q1 = (*A seconds D *+ seconds) +.?;Q1 = (*. )+.?;Q1 = *.9AN

The value of this ;Q1 number is seen when this same patient is tested byanother laboratory usin different prothrombin testin rea ents. ;f the secondlab reported out the same patient with a 8T of *9 seconds and its normalcontrol was *? seconds, is this 8T results the same or different than the firstlabL&ssume that the ;$; number assi ned to their test rea ents is *.M. The


27/53

calculated ;Q1 is +.9. The ;Q1 numbers between the two labs is different and soare the testin procedures. ;f a third lab performed the prothrombin test onthe same patient with the followin results: 8T = +9 seconds, the normalcontrol = *+ seconds, and their ;$Q number is *.+. The calculated ;Q1 becomes+.9. The identical ;Q1 numbers means that there is no difference in the 8T

tests between the last two labs.

T e IN a--ea&s to /e se. .o& -atie*ts < o a&e o* o*9 te&mo&a a*ti'oa9 a*ts a* a e /ee* sta/i i e % T e IN is *ot&e'omme* e .o& -atie*ts < o a&e /e9i**i*9 o&a a*ti'oa9 a*tt e&a- + t e e a atio* t e 'oa9 atio* stat s o. -&es &9i'a-atie*ts+ *o& .o& a -atie*t s prothrombin time to a ;Q1 valueof +.? to .? or possibly .K if the patient has a mechanical heart valve. ;Q1values reater than .? tend to place the patient at ris3 of hemorrha in .

42 DESCRIBE COMMERCIAL THROMBOPLASTIN.

&lso 3nown as tissue factor ;;;, thromboplastin is an or anic e!tract of rabbitbrain or lun tissue suspended in a buffered solution of citrate. This solutionmay or may not have calcium added. ;f the ;$; value of thromboplastin is closeto *.? then the thromboplastin is sensitive. The closer the ;$; value is to +.? theless sensitive the thromboplastin. Commercial thromboplastin is insensitive tofactor ;G due to the concentration of rea ents but if it is diluted, the sensitivityto factor ;G increases but the rea ent becomes less sensitive to factors ;;, ;;,and G.

43 DESCRIBE WHAT FACTORS ARE EVALUATED IN THE FOLLOWINGCOAGULATION SCREENING TESTS.

bleedin clot 8T &8TT TT urea time retraction solubilityG;;; no no no no no yesG;; no no no yes no noG; no no no yes no noG no no yes yes no no;G no no no yes no no;;; no no no yes no no;; no no yesU no no no no no yes yes no no;; no no yes yes no no; no yes yes yes yes no


28/53

6letcher no no no yes no noH#5B no no no yes no no8latelets yes yes no no no noUmost sensiti e

44 DISCUSS THE PROTHROMBIN TIME 0PT1 AS A SCREENING PROCEDURE .This test is also called 'pro time . This is the most often ordered test tomonitor Coumadin oral anticoa ulant therapy. This is the preferred screeninmethod for e!trinsic pathway abnormalities, detectin deficiencies in factors;;, ;;, ;G, and G. ;f the factor concentration is decreased to +? to AK ofnormal, the 8T is prolon ed for one to three seconds. ;n cases ofdysfibrino enemia, where the fibrino en concentration drops to N? m Dd4,the 8T will be prolon ed. ;f factor ;; drops to *? of normal, the 8T will beprolon ed. Other disorders that result in a prolon ed 8T are: [1] dicumarol therapy [6] heparin therapy

[2] factor deficiency [7] factor ;; deficiency [3] obstructive jaundice [8] hemolytic disease of the newborn [4] itamin B deficiency [9] circulatin anticoa ulants [5] factor G deficiency [10] liver diseases

The 8T is a comparison of the patient>s prothrombin time to that of a normalcontrol. ;f the normal control is * seconds and the patients 8T is also *seconds, then there is *?? prothrombin activity. ;f the patient>s 8T e!tends to*N seconds, then the 8T activity will be about K? . ;f the 8T should e!tend toA seconds, then the 8T activity is less than *+ . The physician>s oal incoumadin therapy is to attain an ;Q1 value of +.? to .K or a prothrombin time

that is *.K to + times that of the normal control plasma.. $ee Objective V *.

4" LIST TEN ERRORS THAT CAN OCCUR IN PERFORMING THEPROTHROMBIN TIME.

1! Rsin the incorrect anticoa ulant2! Rsin the incorrect amount of anticoa ulant3! Rsin e!pired rea ents.4! Rsin an incorrect amount of blood to anticoa ulant."! Rsin old or hemoly%ed patient>s plasma#! Rsin wet or dirty plastic ware or lassware in performin the tests.$! 8ipettin errors.:! 6ailure to follow the manufacturer>s directions.;! Chan in from one manufacturer to another and not maintainin

careful "uality control.10! Chan in from one lot number to another without verifyin the

control results.

4# BRIEFLY DISCUSS THE PRINCIPLE OF COUMADIN THERAPY .


29/53

Coumadin is a warfarin compound and competes with vitamin B in the liverpreventin synthesis of the vitamin B dependent coa ulation factors. Coumadinis also 3nown as 5arfarin sodium, Coufarin, 8anwarfin, 5arfilone, and 5arnerinsodium. Coumadin is hydro!ycoumarin and inhibits the carbo!ylation of

vitamin B dependent inactive clottin factors (;;, ;;, ;G, and G). The absence of these carbo!y lutamic acid units leaves these four clottin factors unable tobind calcium ions. The clottin factors cannot con re ate on the phospholipidsurface of the platelet nor to participate in clottin reactions.

5hen a patient is started on coumadin therapy, it become effective in about *?hours. ;t ta3es about two wee3s to stabili%e the patient and for ma!imumtherapy effect. The physician>s intent is to increase the 8T to about *.K to +.?times that of normal. 0ach coumadin dose will be reflected from A to N hourslater. The 8T measures ;; activity, but the activity level of factors ;;, ;G, and Ghas the potential to affect the test.

Clinicians will prescribe oral anticoa ulants to prolon the clottin time, inhibitclottin , and facilitate clot lysis without placin the patient at ris3 of ahemorrha e. 7isorders in which coumadin may be prescribed are:[1] intravascular clottin [6] post operative thrombophlebitis2] pulmonary embolism [7] acute coronary thrombosis

[3] atrial fibrillation [8] recurrin idiopathic thrombophlebitis[4] tissue heart valves [9] recurrin systemic embolism[5] acute embolic and thrombotic occlusions of the peripheral arteries

Coumadin type dru s should not be prescribed for menstruatin women,

pre nant females, nursin mothers, durin postpartum, and followincerebrovascular accidents.. The chief problem with coumadin therapy ishemorrha ic accidents.

4$ DESCRIBE THE THREE TYPES OF ORAL ANTICOAGULANTS USED BYPHYSICIANS.

These are dicumarols, coumarins or coumadins, and indanediones (in dan e dione%). Coumarins are most commonly used. The dicumarols are very slowactin and indanediones have the most side effects. 2ecause of the side effectsindanediones are avoided as therapy strate ies. The antidote for coumarin is

vitamin B, but it may ta3e up to three days to reach it full therapeutic effect.6resh fro%en plasma can immediately correct an emer ency bleedin due tomis dosa e of coumarin. Ca tio* T e&e is some e9&ee o. &is> .o&e-atitis o& AI S i. si*9 .&es .&o e* - asma%

4: LIST MEDICATIONS / DRUGS THAT ARE NOWN AFFECT THE PATIENT4SRESPONSE TO COUMADIN THERAPY .


30/53

5hen a physician prescribes coumadin therapy, a review of what medicationsthe patient is currently ta3in should occur and a prescription written towithdraw andDor add medications. 8atients on coumadin therapy must bemonitored.

7ru s 3nown to potentiate coumadin action are:[1] ethyl alcohol [8] allopurinol[2] anabolic steroids [9] amino lycoside antibiotics[3] tricyclic antidepressants [10] cephalosporins[4] iodine based ! ray dyes [11] heparin[5] oral hypo lycemics [12] penicillin[6] sulfonamides [13] choral hydrate[7] luca on [14] thyroid hormone

7ru s 3nown to depress coumadin effects are:[1] barbiturates [5] corticosteroids

[2] estro ens [6] rifampin[3] !anthines [7] oral contraceptives[4] carbama%epine [8] phenobarbital

4; DESCRIBE THE BASIC PROCEDURE FOR THE ACTIVATED PARTIALTHROMBOPLASTIN TIME 0APTT1 TEST .

The &8TT procedure re"uires placin a desi nated volume of platelet poorplasma (888) into a reaction well followed by a desi nated volume ofcephaloplastin rea ent and allow the mi!ture to come to 9 oC. Three minutesis ample time for step. The final step is to add a desi nated volume of calciumchloride rea ent. The ensuin reaction is watched and the time recorded whenthe fibrin clot develops. This test may miss mild factor deficiencies. Qormalreaction time ran es from a low of +K seconds to a hi h of + seconds.

Ce- a o- asti* is - os- o i-i s /sta*'e o/tai*e /-et&o e m et e& e7t&a'tio* o. a'eto*e &ie /&ai* tiss e% T eAPTT is 'a e -a&tia /e'a se it m st a e t e assista*'e o.t e - asma -&o'oa9 a*ts (e7'e-tio*s a&e .a'to& II a* III)% Itis 'o*si e&e to /e a - ate et - os- o i-o-&otei* s /stit te%

T e testi*9 -&o'e &e &eD i&es a itio* o. a* a'ti ato& to assistt e a'ti atio* o. t e 'o*ta't .a'to&s%

"0 DISCUSS THE PRINCIPLE OF THE ACTIVATED PARTIAL THROMBOPLASTIN TEST.

The activated partial thromboplastin test (&8TT) is also simply called thepartial thromboplastin time (8TT) test. This test evaluates the intrinsic clottinsystem. The &8TT test monitors 6letcher, 6it% erald, G;;, ;;;, ;G and G;


31/53

coa ulation factors. This rea ent contains a contact factor (Baolin, ella ic acid,or celite) which induces conformational chan es in Ha eman (G;;) factor andinitiates the coa ulation cascade mechanism. #ost coa ulation factordeficiencies and circulatin anticoa ulants involve these factors, thereforecoa ulation investi ations should include the &8TT as a testin strate y. &8TT

rea ent are calibrated to provide prolon ed values when the patient>s plasmahas ?. unitsDm4 of factors ;;;, ;G, and G;. The &8TT is also prolon ed whenlupus anti coa ulant antibody is present. The &8TT is insensitive to factors ;;and G;;;.

"1 LIST THE CIRCUMSTANCES IN WHICH A PHYSICIAN WOULD ORDER AN ACTIVATED PARTIAL THROMBOPLASTIN TIME .

5hen the patient is suspected of havin a hemorrha ic disorder or thephysician suspects a lupus anticoa ulant antibody. The followin are 3nown tocause prolon ed &8TT>s:

1! deficiencies of factors ;;, , ;;;, ;G, G, G;, or G;;.2! fibrino en level *.? m Dd43! anti factor ;;;4! fibrin de radation products (678)"! disseminated intravascular coa ulation#! vitamin B deficiency (The &8TT detects only 6actors ;;, ;G, and G)$! heparin therapy.

5hat 3ind of an &8TT test result is the physician loo3in for in heparin therapyL$ince the normal ran e is from +K to + seconds with a median time of Mseconds, the physician is loo3in for a therapeutic time of about KN seconds.

This is abut *.K times that of the median time.

"2 DESCRIBE THE LUPUS ANTI-COAGULANT ANTIBODY .

This antibody is found in up to *? of patients with systemic lupuserythematosus ($40), hence its name. ;t is also found in viral infections inchildren and H; . This antibody has an affinity for phospholipid, anti factor ;;;antibody, and heparin. ;t will combine with the test rea ents for &8TT. The'lupus antibody may cause false positive serolo ical tests for syphilis. ;tspresence causes prolon ed 8T and &8TT time results, but rarely causeshemostatic problems. The antibody is more often associated with thrombosis

problems rather than those of bleedin . ;t is not 3nown to activate clottinfactors. The antibody is either ; # or ; < or both. ;t binds to the phospholipidsbloc3in interaction in the coa ulation scheme.

This antibody is difficult to identify in the laboratory. The followin are a fewsteps to follow in order to identify the antibody.[1] Carefully collect the blood specimen and centrifu e to remove allplatelets because they will inactivate the antibody.


32/53

[2] 1ule out heparin contamination. The thrombin time or reptilase test willaccomplish this.[3] #i! one part of the patients plasma with one part of normal plasma. Thiswill correct the problem if it is a one factor deficiency. There will be nocorrection for the presence of the antibody. 1efer to Objectives 9+ and N+.

[4] & 1ussell viper venom time (see Objective N*) or 3aolin clottin time willhelp to screen for the antibody. ;f these antibodies are present these tests willbe prolon ed.

"3 DESCRIBE HEPARIN AND ITS MODE OF ACTION .

Heparin (a sulfated polysaccharide) is a proteo lycan (a acidicmucopolysaccharide) found inside mast cells and basophils, lun , liver, s3in,and in circulation. ;t is a hetero enous molecule that consist of severalcomponents that can be separated by molecular si%e and wei ht. ;t is a uni"uemolecule containin many sulfate roups. One of its 3nown functions is to

activate antithrombin ;;; and another function is to interact with factor G,prothrombin, and platelet a re ation. Ca tio* He-a&i* s o *ot /ese to 'o e't / oo .o& - ate et 'o *ts% ;t can be isolated from the liver,lun s, and spleen. ;t is poorly absorbed from the s baseline or controlvalue. &s a rule this puts the heparin concentration to about ?. to ?.KunitsDm4. $ide effects of heparin therapy are hemorrha e and development of

thrombocytopenia.

Heparin is thou ht to have bindin sites for thrombin and antithrombin ;;;. 2ycomple!in with thrombin and antithrombin ;;;, heparin can induce aconformational chan e in antithrombin ;;; and facilitate the formation ofcovalent, one on one thrombin antithrombin ;;; comple!, thus speedin up therate at which antithrombin ;;; reacts with thrombin. One possible mode ofaction is listed as follows:


33/53

"4 DISCUSS THE ROLE OF PROTAMINE SULFATE IN COAGULATION .

;t does not have a direct role. ;t is a simple protein that has been sulfated toform an anta onist to heparin. One m of protamine sulfate will neutrali%e *??

units of heparin. ;t is also a test procedure to evaluate the action of thrombinon fibrino en. $ee Objective N9.

"" DISCUSS ANTITHROMBIN-III AS A NATURAL INHIBITOR OF COAGULATION .

&ntithrombin ;;; (&T ;;;) is a sin le chain, F+ lobulin, produced in the liver,and is a major inhibitor of coa ulation. ;t is responsible for about N? ofcoa ulation inactivation. ;ts an anti serine protease, whose primary tar et isinactivation of thrombin. ;t also inactivates any activated serine proteaseclottin factor (;G, G, G;, and G;;). &lso inactivated are protein C and 6letcherfactor. &T ;;; contains an ar inine residue that interacts with the active serine

molecule of the coa ulation en%yme.;t is decreased in thrombotic disease, disseminated intravascular coa ulation(7;C) syndromes, cirrhosis of the liver, certain liver diseases, followin sur ery,septicemia, and women on oral contraceptives or estro en therapy. ;t isassayed usin electro immunoassay, radial immunodiffusion, or en%yme lin3edimmunosorbent assay. Qormal ran es (*9 to ? m Dd4) are listed as low as 9?and a hi h of *+K . Qormal ran es are established by individual laboratoriesand will vary from lab to lab. ;f &T ;;; levels drop to A? that of normal, thepatient is at ris3 of a thrombosis.

"# DISCUSS PROTEIN C AS AN INHIBITOR.8rotein C (a lycoprotein) is vitamin B dependent and produced in the liver.8lasma levels avera e from to K m D4. ;t is activated by thrombin and also apotent inhibitor of 6actors ;;; and G. The activation of protein C is enhancedand accelerated by the presence of thrombomodulin and Ca EE. 0ndothelial cellscontain thrombomodulin molecules which interact with thrombin formin a *:*comple!. The comple! forms a modified thrombin molecule that is not free to


34/53

cleave fibrino en, but is available to activate protein C. ;n this way thrombinbecomes an anticoa ulant. &ctivated protein C (comple!ed with protein $)destroys activated factor , which limits the formation of thrombin. Thisprotein C activity ma3e activated factor G more vulnerable to deactivation byantithrombin ;;;. 8rotein C also enhances the release of tissue plasmino en

activator by inactivatin a plasma inhibitor of tissue plasmino en activator."$ DISCUSS THE ROLE OF PROTEIN S IN THE INHIBITION OF HEMOSTASIS .

8rotein $ is a vitamin B dependent lycoprotein and e!ists in plasma in twoforms. 6orty percent of 8rotein $ e!ists in the functional free form and theremainder e!ists in a form comple!ed to C b bindin protein (lin3ed to thecompliment system) which is non functional. The amount of 8rotein $ in plasmais from +? to +K m Dd4. Qormal laboratory ran es for 8rotein $ ran es from Ato *A? . ;f protein $ levels fall to W A? , then the patient is at ris3 forthrombotic complications. 8rotein $ is synthesi%ed by hepatocytes and

me a3aryocytes. This protein has a hi h affinity for phospholipid surfaces andepithelial cells. This affinity promotes the bindin of 8rotein C to such surfacesand facilitates 8rotein C activation. 6ree protein $, in bindin to 8rotein C,forms a comple! with 8rotein C. ;t is this comple!ed form of 8rotein C that actsupon specific clottin factors.

": DISCUSS 5% - MACROGLOBULIN AS A COAGULATION INHIBITOR.

F+ #acro lobulin is a lycoprotein found throu hout the body. This protein willform comple!es with thrombin, plasmin, and 6letcher factor (3alli3rein) toinhibit their activities. The F + macro lobulin will bind slowly with thrombin,

then under o cleava e, leavin the thrombin molecule less effective in itsproteolytic activity. ;t appears that the comple!es formed by the F + macro lobulin tend to be cleared from plasma by pha ocytic cells of the#ononuclear 8ha ocytic $ystem (#8$), formerly the reticuloendothelial system(10$). &bout K? of the inhibition of 6letcher factor is conducted throu h themacro lobulin. F + #acro lobulins are in the hi hest concentrations in infants,small children, and pre nant women. ;t is reported that this lycoprotein canform comple!es with serine proteases.

"; BRIEFLY DESCRIBE THE PURPOSE OF C#-INACTIVATOR IN THEINHIBITION OF HEMOSTASIS.

C* ;nhibitor (also called C* inactivator) is a neuramino lycoprotein. ;t is theprinciple inactivator of activated factors G; and G;;, plasmin, and activated6letcher factor (3alli3rein).

#0 BRIEFLY DESCRIBE THE PURPOSE OF 5# - ANTITRYPSIN IN THEINHIBITION OF HEMOSTASIS.


35/53

F* &ntitrypsin is a lycoprotein, which is thou ht to have a secondary role incoa ulation inactivation. ;t is considered to be a wea3 inhibitor of thrombinand activated factors G and G;.

#1 BRIEFLY DESCRIBE THE PURPOSE OF HEPARIN COFACTOR II IN THE

INHIBITION OF HEMOSTASIS.Heparin cofactor ;; is a lycoprotein synthesi%ed in the liver. ;ts activity isstron ly au mented by heparin, indicatin that it has limited activity by itself.;t is limited in its substrates, suppressin thrombin and chymotrypsin. There isno 3nown evidence of activity a ainst activated factors ;G, G, and G;.

#2 DISCUSS THE ROLE OF VITAMIN IN HEMOSTASIS.

itamin B is re"uired by the hepatocytes to complete the alteration of factors;;, ;;, ;G, and G. ;t converts the lutamic acid residue in these factors to a

carbo!y lutamic acid residue that has the capability to bind calcium ions.

itamin B*, typical of plants, is found in reen leafy ve etables. 2acterial flora(Escherichia coli , 2acteroides fragilis , etc.) in the intestinal tract synthesi%esvitamin B+, a useable form characteristic to animals for absorption. ;f thepatient has mal absorptive syndrome of the


36/53

cross lin3in occurs. This means that plasmino en will de rade at this site.Cleava e of the fibrin clot produces the followin products: first a XXD7G7comple!, second . . . 707 and 7XDX7 comple!es, and third . . . 0 fra ment, 77 dimers, and 707 comple!es. The followin de radation scheme illustrates thede radin process.

#4 DISCUSS THE ROLE OF PLASMINOGEN IN THE FIBRINOLYTIC SYSTEM.

8lasmino en is a sin le chain @ lobulin that circulates in the blood in aninactive state. The plasma concentration ran es form +? to ? m Dd4. ;t isproduced in the liver. ;t is drawn into the clottin process in its inactive formand becomes absorbed into the clot. &ctivators of plasmino en (t 8&) can befound in the blood and most tissues. &ctive coa ulation factor G;;, 6letcher(3alli3rein), and 6it% erald (H#5B) convert plasmino en to plasmin. These aredesi nated as intrinsic activation. 0!trinsic activation occurs when theendothelial cells of the vascular system release tissue activator, whenstimulated by certain activated clottin factors, e!ercise, hypotensive shoc3,pharmacolo ic stimulators, and venous stasis.

#" DISCUSS THE ACTIVATION OF PLASMINOGEN TO PLASMIN.

8lasmino en activator factor (t8&) has a stron affinity for fibrin and it is


37/53


38/53

thrombin, plasmin, and 3alli3rein. ;t is considered to be an important bac3upinhibitor when F + antiplasmin levels are low. This is a very lar e molecule andit mode of action is to trap the plasmin molecule as it attempts to attachproteolytically to a substrate molecule. The level of inhibition is not ascomplete as for F + antiplasmin since the bound molecule can e!ert small

levels of activation. 7eficiencies of this inhibitor are rare and medically thesepatients are asymptomatic.3! 8&; * is produced in the hepatocytes, endothelial cells, andme a3aryocytes. 8&; * is found in the F ranules of platelets. 8&; * inhibitstissue plasmino en activator (t 8&) and two chain type lycoprotein (uro3inaseli3e) plasmino en activator (tcu 8&) by neutrali%in the molecule andpreventin it from formin plasmin.

The e!trinsic plasmino en activators desi nated as uro3inase typeplasmino en activator e!ists as two types -*/ scu 8& and -+/ tcu8&. The scu 8& (sin le chain type lycoprotein (uro3inase li3e)plasmino en activator) molecule does not activate plasmino en,but tcu 8& does.

4! 8&; + wea3ly inhibits t 8& and tcu 8&, but not scu 8&."! 8&; inhibits tcu 8& and activated protein C.

Note PAI - asmi*o9e* a'ti ato& i* i/ito&%

#: DESCRIBE THE LEE-WHITE WHOLE BLOOD CLOTTING TIME .

This testin procedure is included for its historical interest. ;t will not be usedfor test "uestions. This is a whole blood clottin time test that has been usedto monitor heparin therapy. 8repare three N.? mm diameter tests tubes for thetest. 6our m4s of blood is drawn with a +? au e needle via a clean, nontraumati%ed venipuncture. One m4 of blood is deposited in each of the threetest tubes and the last m4 is discarded. The tubes are placed in the water bathfor three minutes. 2e in loo3in for clot formation as follows: 1! Tilt tube V*at ? second intervals until the blood can be completely inverted withoutspillin . 2! 1epeat with tube V+, and 3! lastly with tube V . Qote that thehandlin and tiltin of blood hastens the clottin process. The results obtainedfor tube V are reported. & prolon ed clottin time is considered to beindicative of a coa ulation deficiency. The normal ran e for the 4ee 5hiteclottin time is five to ten minutes. ;f the tube diameter is M.? mm, then thenormal ran e increases to si! to thirteen minutes. This clottin procedure isconsidered obsolete and is no lon er performed. The prothrombin time (8T)and activated partial thromboplastin time (&8TT) tests involve the samecoa ulation time principle and are more reliable. Comments . . . . Tube V* maybe left in the water bath over a + to hour period and observed for clotretraction. The tiltin of the tubes are to be entle, always in the samedirection, and at the same an le.


39/53

#; DISCUSS THE ACTIVATED COAGULATION TIME 0ACT1 TEST .

The activated coa ulation time (&CT) test is a modification of the whole bloodclottin time test. ;t is a test desi ned to be performed at the bedside of the

patient. ;t is used to monitor heparin therapy. The test re"uires the use of atube that contains an activator (e!ample: diatomaceous earth) to which mustbe added a minimum of +.? m4s of whole blood. The blood is mi!ed todistribute the activator and timin be ins as soon as the blood is collected. Thetube is tilted and observed until a clot is formed. The mean normal time forthe clot to form is MN seconds. ;f a person is on heparin therapy for deep veinthrombosis, the e!pected clottin time ran es from *N? seconds ( minutes) to+ ? seconds ( minutes). & person on heparin therapy for cardiopulmonarybypass operation should demonstrate a mean clottin time of ?? seconds (9minutes).

$0 BRIEFLY DESCRIBE THE ROLE OF URO INASE AND STREPTO INASE INHEMOSTASIS THERAPY .

Rro3inase and strepto3inase are thrombolytic dru s used to treat pulmonaryemboli and coronary thrombosis. These dru s will activate plasmino en toplasmin. These dru s are usually iven via ; infusion and can induce a hi hde ree of fibrinolysis.

$1 DISCUSS THE BLEEDING TIME IN THE INVESTIGATION OF HEMOLYSIS .

The bleedin time is an in vitro testin procedure to detect platelet

dysfunction and von 5illebrand>s disease which will prolon the bleedin time.2ecause aspirin causes prolon ation of the bleedin time in normal patients,this procedure should not be attempted on patients who have ta3en aspirinwithin the past ei ht days. 7ru therapy may also prolon the bleedin time.Thrombocytopenia prolon s the bleedin time.

The 7u3e method (introduced in *M*?) is the least reproducible of the bleedintime techni"ues. ;t is not lon er performed in most laboratories. The ;vymethod replaced the 7u3e procedure in *M *, which employs a blood pressurecuff on the arm of the patient. The 'cuff is inflated to ? mm H . Two orthree lancet incisions (about * mm deep and ?. mm lon ) is made on the

inside forearm and the bleedin time of the two or three cuts avera ed. Thismethod reatly improved the bleedin techni"ue with more reproducibleresults. $evered capillaries tend to collapse (vaso spasm phenomenon) whichshortens the clottin time and is independent of platelet function. The 7u3emethod had three variables and the ;vy method eliminated the capillaryvariable. This left the platelet function variable and the human variable of thecapillary puncture. ;n *MAM, the template method was introduced in which amechanical device produces a standardi%ed len th and depth of cut (* mm


40/53

deep and mm lon ), removin the human variable. The template bleedintime is reproducible and the preferred techni"ue. Qormal template bleedintime values ran e from +. minutes to M.K minutes. The direction of the cut onthe forearm should be consistent for all patients, either perpendicular(vertical) or hori%ontal to the bend of the elbow. Hori%ontal incisions tend to

yield lon er bleedin times. Caution: T e tem- ate met o 'a* 'a semi to si9*i8'a*t s'a&&i*9 i* some -atie*ts%

$2 EXPLAIN WHY A PHYSICIAN WOULD ORDER A THROMBIN TIME 0TT1TEST .

This test (synonym: thrombin clottin time) measures the availability offunctional fibrino en. The prothrombin time will be prolon ed when 1! thefibrino en level drops to 9K m Dd4 to *?? m Dd4, 2! if heparin is present, 3! if fibrin or fibrino en de radation products are present, and - / a thrombolytica ent (as strepto3inase) is present. The prothrombin time is not specific, but

can detect a 6actor ;; deficiency. ;f the physician suspects heparin inhibition,then the thrombin time (TT) test will help to confirm this problem. Theprocedure re"uires citrated plasma (one part ?.*?M # sodium citrate in M partsof whole blood). The specimen must be centrifu ed to obtain platelet poorplasma. The plasma must be 3ept cold and the test performed within fourhours after collection. Qormal values are determined by the thrombinconcentration used. 1eference ran es may be 1! N M seconds, 2! *K to +?seconds, 3! less than + seconds, or 4! +? to +K seconds. Caution

T &om/i* is *ot a sta/ e &ea9e*t+ o*'e it is ma e - a* es a/o t t &ee mi* tes)+ it m st /e se imme iate ( s a


41/53

retraction is abnormal when para proteins are present (as in multiplemyeloma), thrombocytopenia, s thrombasthenia, 2ernard $oulierdisease, dysfibrino enemia, and disseminated intravascular coa ulation (7;C).Observe the followin illustrations of a normal and abnormal clot retraction.This test is seldom performed in the laboratory. ;t is included to describe how

blood behaves in the clottin process.

Comment: T e ' ot &et&a'tio* test is 9e*e&a 'o*si e&e to /e o.itt e ' i*i'a se% T e mo&e so- isti'ate - ate et . *'tio* test a ema e t is -&o'e &e a se om &eD este -&o'e &e%

$4 EXPLAIN THE CONCEPT OF AGGREGOMETRY AS A PLATELET FUNCTIONTEST .

This testin procedure re"uires special 'a re ation rea ents and a specialphotometer with a stirrin device. 2lood must be collected with a plasticsyrin e and stored in plastic tubes. The blood is centrifu ed at as speede"uivalent to *K? G for ? minutes to prepare a platelet rich plasma (818). ;f

12C>s appear to be present in the 818, repeat this centrifu ation step a ain forK minutes. & platelet poor plasma (888) must also be prepared by spinnin at*K?? G for *K minutes. Cap the specimens in a plastic tube to prevent CO + loss and pH chan es. 8erform a platelet count to determine the plateletconcentration in the 818. ;f the count is between +?? G *? MD4 and ?? G *? MD4,proceed with the a re ometry studies. ;f the count is reater than ?? G*?MD4, adjust the sample by dilutin it with 888. 1epeat the platelet count forverification. & desi nated volume (usually ?.K m4 of 818) is placed in thea re ometer well or cuvette and appropriate a re atin rea ent is added.The optical density of the specimen is monitored and as a re ation ta3esplace the specimen becomes clear and the li ht transmittance increases. &ll

chan es in optical density over time are recorded in a raph format as a curve.;f the curve deviates from the normal e!pected curve, the slope of the curvechan es and forms the basis for determinin the amount or percent of plateleta re ation. 0!amine the followin illustration of the features of the plateleta re ation curve.

The principle of platelet a re ometry is to deliberately add a plateleta re atin a ent to 818, induce shape chan e and then cause the platelets to


42/53

a re ate or clump to ether. 5hen the test is initially set up, thea re ometer (type of photometer), the suspended platelets form a turbidsuspension. &s a re ation ta3es place the test suspension clears and a chan ein the li ht transmission is measured and recorded. The test procedure re"uiresthat the patient be in a fastin state and that their last meal be fat free. The

patient should not be ta3in aspirin or non steroid anti inflammatorymedications. The patient>s blood is to be drawn with a plastic syrin e and theblood added to .N sodium citrate. The blood to citrate ratio is nine partsblood to one part anticoa ulant. Testin for platelet a re ation should becompleted within two hours after collection. $ee the followin illustration forplatelet a re ation scheme.

$" DISCUSS SIX PLATELET AGONISTS USED IN AGGREGOMETRY STUDIES.

EPINEPH INE . &lso called adrenalin, it produces a biphasic curve ofirreversible platelet a re ation. & small percenta e of patients willdemonstrate a monophasic curve. &bnormal platelet curves are observed inthrombosthenin, uremia, and stora e pool disease.Storage !ool Disease ! This is a platelet disorder characterized by theabsence of dense bodies and or 3-granules! &latelets cannot release 1&,calcium, platelet factor-4, etc! This is obser ed in 5is"ott- ldrich syndrome,thrombocytopenia ( ith absent radius bone in both arms) "no n as T 0, and$hedia"-#igashi syndrome! There is no treatment for this platelet disorder!A ACHI ONIC ACI . 5hen this rea ent is added to the patient>s specimen, asin le monophasic curve is produced, resemblin that produced by colla en. ;fthere is a platelet deficiency of thrombo!ane andDor cycloo!y enase, the curveis suppressed. &spirin inhibits this rea ent resultin in the absence of a curve.The patient must be aspirin free for ei ht days before testin . &bnormal curveresults are observed in thrombasthenia. Note A&a' i o*i' a'i is eat a*i9 t a/i e a* m st /e sto&e i* t e .&o e* state a


43/53

-e&missi/ e to &e.&ee e a&a' i o*i' a'i a iD ots t &ee times%COLLAGEN . 5hen colla en is added to a patient>s specimen the rea entinitiates a monophasic curve after ? to A? seconds. This a re ationphenomenon is dependent upon an intact platelet membrane and membranereceptors, normal phospholipase pathway, and normal cycloo!y enase and

thrombo!ane functions. ;f an abnormal response occurs, this may su estdisorders such as platelet membrane defect, stora e pool disorders, aspirin li3edefects, thrombasthenia, and uremia. NOTE Co a9e* s o *ot /e.&o e*% Sto&e at &e.&i9e&ato& tem-e&at &e%

As-i&i*= i>e e.e'ts is a* a*oma t at es'&i/es - ate ets


44/53

$$ EXPLAIN THE PRINCIPLE OF THE PLATELET ADHESIVENESS TEST .

This is an in vitro procedure to evaluate the ability of platelets to adhere toeach other and to walls of dama ed vessels. Two samples of blood is collected,one specimen collected under standard procedures in an 07T& tube and theother into a similar tube but re"uirin the blood to pass throu h a tubinpac3ed with lass beads. ;f the platelets are normal, the second tube willcontain from ? to 9K of the platelets counted in the first tube. The adhesivenature of the platelets will cause them to adhere to lass beads. The resultsreported reflect the number of platelets that adhered to the lass beads.7etermine the difference between the two values and divide the difference by


45/53

the count without beads and multiply the result by *??? to obtain thepercenta e. Qormal values reported are variableI from a low of +A to a hi hof MK platelet adhesion. This test is difficult to interpret. Decreased !a"#es are observed in 1! s thrombasthenia, 2! von 5illebrand disease,3! Chedia3 Hi ashi syndrome, 4! certain myeloproliferative disorders, "!

uremia, and #! in estion of dru s andDor aspirin. Increased !a"#es areobserved in 1! venous thrombosis, 2! pulmonary embolism, 3! carcinoma,4! pre nancy, "! splenectomy, and #! patient>s ta3in oral contraceptives.

$: DISCUSS THE CIRCULATING ANTICOAGULANT TEST .

$ome coa ulation problems are due to the presence of inhibitors, somethinthat interferes with the coa ulation mechanism, and are not due to adeficiency of a coa ulation component. These may develop because of somedisease state or an idiopathic problem. $uch inhibitors are ; < antibodies (someantibodies are reported of the ; # class). There are two roups of circulatin

inhibitors:1! S-e'i8' i* i/ito&s . . . . This roup are antibodies and are directeda ainst certain coa ulation factors. These often react in a pro ressive mannerand tend to be irreversible. The inhibitors that are seen the most are thosedirected a ainst factors ;;; and ;G.2! No*=s-e'i8' i* i/ito&s . . . . These are not directed a ainst any specificcoa ulation factor. Qon specific inhibitors may not be associated with bleedin .These are immediate in action and will form a protein protein comple! with aspecific factor or roup of factors. $uch comple!es are reversible and enerallydo not destroy the factor(s). The lupus li3e roup of circulatin inhibitors arespecific a ainst phospholipids and do not cause bleedin . &nother roup of

inhibitors seen in this cate ory are seen in patients with multiple myeloma orbeni n paraprotein disorders. 4iver disease may result in the development ofnon specific inhibitors.

These inhibitors can be detected by the activated partial thromboplastin time(&8TT) test and sometimes by the prothrombin time (8T) test. To determine ifthe abnormal result is due to a coa ulation factor deficiency or a circulatinanticoa ulant or inhibitor, repeat the test by mi!in one volume of thepatient>s citrated plasma with an e"ual volume of normal plasma. ;f the causeis due to a coa ulation factor deficiency, the &8TT test result will be normal. ;fcirculatin inhibitors are present the patient>s plasma will not be corrected and

the results will be prolon ed. The reason that the patient>s plasma would becorrected if the problem were a coa ulation deficiency is that it re"uires aboutK? of the coa ulation factors to produce a normal test result.

$; EXPLAIN THE DIFFERENCE BETWEEN AGED AND ABSORBED PLASMA INCOAGULATION STUDIES AND HOW TO INTERPRET THE RESULTS OBTAINED .

& ed serum is obtained by allowin a tube of clotted normal blood to incubate


46/53

at 9 ?C for three hours. One procedure re"uires that to this tube of blood, addone part of ?.*?M # sodium citrate to nine parts of whole blood. &llow theblood to incubate an additional two hours. Centrifu e for ten minutes andremove the serum. The serum is ready to be used. The second procedurere"uires that the clotted blood be centrifu ed without the addition of

additives. ;f stored, store at +??

C. 5hen usin a ed serum, dilution may bere"uired. ;f so, use ?.NK QaCl. & ed serum contains factors ;;, ;G, G, G;, andG;;. ;ncubation destroys the labile factors.

&bsorbed plasma is made by addin *?? m of barium sulfate to each m4 offresh o!alated plasma (use sodium o!alate). QOT0: &luminum hydro!ide elmay be used but re"uires fresh citrated plasma, use sodium citrate. #i! themi!ture for ten minutes at room temperature, then place in the refri eratorfor an additional ten minutes. Centrifu e at +K? rpm for ten minutes andremove the supernatant plasma. 2arium sulfate or aluminum hydro!ide willabsorb out factors ;;, ;;, ;G, and G. &bsorbed plasma contains factors ;, , ;;;,

G;, and G;;.To use either absorbed plasma or a ed serum, mi! e"ual parts with thepatient>s plasma and perform the &8TT or 8T test. 0!amine the followin tableto see how substitution studies mi ht reveal the factor deficiencies. Q = normal, & = abnormal, and U = testin not re"uired. &robable 2%O02E1 &. %6 7E1 %E086 factor

&TT &T &TT &T &TT &T deficiency

& Q Q U Q U G; or G;;

& Q & U Q U ;G & Q Q U & U ;;; Q & U & U Q ;; & & & & Q Q G & & Q Q & & & & U U U U ;; Q Q Qo deficiency

:0 BRIEFLY DESCRIBE THE UREA SOLUBILITY TEST.

The urea solubility test is specific for factor G;;; deficiency. ;t is also called the

6actor G;;; $creenin Test. 1outine coa ulation screenin tests do not detectfactor G;;; deficiency. To perform this test, add calcium to citrated plasma toform a fibrin clot. Qe!t add K# urea to the clot and incubate at roomtemperature for + hours. ;f there is no deficiency, the clot will remain intact.;f factor G;;; is missin , the clot will dissolve in this period of time. This testwill detect a factor G;;; deficiency if MN of the factor is defective or missin .

:1 EXPLAIN WHY A PHYSICIAN WOULD ORDER A STYPVEN TIME TEST .


47/53


48/53

TIME.

He probably would not order this test. ;f he did, it would be to measurefibrinolytic activity. Qormal fibrinolysis occurs at a slow rate in the eu lobulinsystem. ;f a firm clot is present after M? minutes, the fibrinolysis process is

normal. ;f the clot is lysin and deterioratin in the first M? minutes, thenfibrinolysis is increased and abnormal.

The procedure is simple. 8lasma is acidified with cold dilute acetic acid untilthe solution attains a pH of K. K to K. ?. The ne!t step is to refri erate themi!ture for ? minutes, in which time a precipitate should form that containsfactor ;, plasmino en, plasmin, and plasmino en activators. This precipitate isthe eu lobulin fraction. Centrifu e the tubes and decant the supernatant.1esuspend the residue in borate buffer, then add thrombin. 2e in timin .;ncubate at 9 oC. The clot will form in a short time. Chec3 the clot every tenminutes for lysis. ;f no lysis after M? minutes, the test is complete. 1eport as

normal. ;f the time is shorter, then this indicates increased plasmino enactivator activity.

:" EXPLAIN WHY A PHYSICIAN WOULD RE2UEST A TEST TODEMONSTRATE THE PRESENCE OR ABSENCE OF FIBRINOGEN DEGRADATIONPRODUCTS.

6ibrino en de radation products (678), also called 6ibrin $plit 8roducts (6$8)are observed in patients with acute and chronic disseminated intravascularcoa ulation, alcoholic cirrhosis of the liver, sur ical complications, primaryfibrinolysis, late pre nancy, deep vein thrombosis, and pulmonary embolism.

The very presence of 6$8 in these e!amples indicate that a plasmin release hasoccurred or is occurrin . 8atholo ic de radation of fibrino en and fibrin are theresult of increased plasmin activity and sets the state for abnormal secondarybleedin . 678>s are si nificant because that they have hemostatic effects(includes antithrombin activity and interference with platelet activity andfibrin monomer polymeri%ation) and can be life threatenin . 6ibrino enfra ments into G, X, 7, and 0 fra ments and other low molecular wei htproducts. ;t is the G and X fra ments that e!ert the anticoa ulant effects bypolymeri%in with fibrino en. The X and 7 fra ments obstruct thepolymeri%ation of fibrin which results in soluble fibrin formation. The 0fra ments is inhibitory to thrombin. ;n addition, all the fra ments are capable

of adherin to platelet surface membranes and causin platelet dysfunctionwith poor a re ation properties. These comple!es can be detected by theprotamine sulfate test, ethanol el test, and late! 678 assay.

:# DIFFERENTIATE BETWEEN PRIMARY AND SECONDARY FIBRINOLYSIS.

P&ima& 8/&i*o sis (PF) , a rare event, is the de radation of fibrino en. Thisis a patholo ical state characteri%ed by increased amounts of plasmino en


49/53

activators, increasin the amount of plasmin in circulation. This results also inthe splittin apart of factors and ;;;. The fibrino en de radation productsform fibrin li3e threads slowly and re"uire about + hours for the evidence of'clottin to appear. This is not a common occurrence but appears whendama ed cells appear or mali nant cells (as in prostate cancer) are present,

sur ery, shoc3, acute leu3emia, or cirrhosis of the liver.Se'o* a& 8/&i*o sis (SF) occurs in conditions li3e disseminatedintravascular coa ulation (7;C) where there is deposition of fibrin. $econdaryfibrin de radation products tend to polymeri%e earlier, re"uirin about ?minutes to become observable.

There are four tests that will differentiate between these two types offibrinolysis.1 ! The 0u lobulin Clot 4ysis Time. ;t is si nificantly decreased in primaryfibrinolysis.

2! 8latelet count. ;t is increased in 86 (Y*?? G *?MD4). ;n $6 the plateletcount is usually less.3! &ntithrombin ;;; assay. 4evels will be normal in 86, but decreased in $6.4! 7 dimer test will be ne ative in 86, but positive in $6.

:$ EXPLAIN THE PRINCIPLE BEHIND THE PROTAMINE SULFATE DILUTION0PSD1 TEST.

6ibrin de radation products (678) are soluble entities that interfere with thenormal coa ulation process. ;f protamine sulfate is added to plasma containin678>s, then a variation of a phenomenon 3nown as paracoa ulation ta3es place.

This means that the various 678>s will be in to dissociate from fibrin and othersites and will polymeri%e in the presence of protamine sulfate to form aelatinous button. The button is comprised of G and XX fra ments. 6irbrinmonomers will also join this odd polymeri%ation phenomenon. Qote if 678 arepresent in lar e "uantities, the test will not wor3 well. The protamine sulfate(also true for ethanol) will displace the small 678>s resultin in spontaneouspolymeri%ation. 6or this reason the protamine sulfate dilution test and theethanol elatin test can be used to tests for 678>s. The better testintechni"ue is & arose el chromato raphy. Caution t e 9e is sometimesi ' t to o/se& e% La/o&ato&ia*s < o &ea t e PS test &eD i&ee7-e&ie*'e% 6alse positives occur in females before and after menses and in

patients with advanced cirrhosis. This test does not detect just fibrino ende radation products. ;f fibrino en is present in lar e "uantities, it tends toprecipitate as an amorphous mass which occurs as lar e 678 comple!es withfibrino en. This is not a elatinous clot.

B e8*itio*+ -a&a'oa9 atio* o'' &s < e* t &om/i* s- its8/&i*o9e* i*to 8/&i* mo*ome&s% T e 8/&i* mo*ome&s


50/53

sta&t .o&m a 8/&i* mes ( e e o-me*t o. t e ' ot)% T e8/&i* mo*ome&s


51/53

1! 8ossibility of transferrin activated coa ulation factors on the probe>selectrode into the ne!t patient>s sample and shortenin of the clottin time.2! Rse of incorrect reaction wells or cups.3! Technical error on the part of the laboratorian.

4! ;ncorrect collection of the specimen."! 0!pired rea ents.

;1 DISCUSS THE OPERATION PRINCIPLE OF THE PHOTO-OPTICALCOAGULATION INSTRUMENT, SUCH AS THE COAG-A-MATE, MDA, OR MLA .

These instruments come in a variety of models and use a photocell to detectthe fibrin clot. They have an advanta e over the electromechanical detectionsystems in that the photo optical detector can detect a rapid and si nificantincrease in li ht transmission. &ccuracy is e!pected to be S ?.* seconds. Thespecimen and rea ents are pipetted into the reactions wells in such a way that

ma!imum mi!in is obtained. There is no movin probe to mi! the system asre"uired in the fibrometer. &ccuracy of rea ent and specimen delivery ismaintained by sensor systems that cause the probe(s) to ma3e minimal contactwith the fluids. The technolo y and sensitivity of these instruments permitsdetectin clots in chylous and icteric patient specimens.

;n detectin the formin clot, at the onset of the test, the li ht is transmittedthrou h the reaction mi!ture with little scatterin . &s the reaction proceedsand more and more fibrin is incorporated into polymers, then into the clot, theamount of li ht scatterin increases proportionally. This creates an electricalsi nal that is analy%ed by al orithms. &t some point in the reaction, the si nal

becomes such that the instrument determines that the clot has formed. & timeris lin3ed into the reaction which is turned on when the plasma is added to therea ents. & detection system also turns on at the same time and it will turn offthe timer when the formation of the clot occurs.

A* a 9o&it m is a se&ies o. a 9e/&ai' eD atio*s% T ismea*s t at it is a* o& e&e seD e*'e o. ste-s% Ea' ste-m st /e 'om- ete /e.o&e t e *e7t ste- 'a* -&o'ee % T ismat emati'a st&ate9 is -&o9&amme i*to a 'om- te& asa se&ies o. mat emati'a -&o9&essio*s to e*a/ e it to set e e9&ee o. i9 t s'atte&i*9 as a mea*s to ete&mi*e t e'om- etio* o. t e ' ot%

;2 LIST SEVEN SOURCES OF ERROR THAT MAY OCCUR IN THE PHOTO-OPTICAL DETECTION COAGULATION SYSTEM.

"#$ The possibility of a ripplin optic effect that occurs when rea ents andspecimen are added to the reaction chamber and causin the instrument to


52/53


53/53

;! 8erform statistical calculations to establish standard deviations.

;" . DISCUSS PROFICIENCY TESTING IN THE COAGULATION LABORATORY.

This is a "uality control pro ram for interlaboratory testin to evaluate the

coa ulation results. 2y comparin the test results between the patient and thecontrols, the laboratory can access their performance to that of otherlaboratories. This increased the reliability of the test results reported to thephysician. 5hen comparin results with other laboratories, use thoselaboratories that use the same testin instruments and rea ents used in yourlaboratory. ;n coa ulation testin , the prothrombin time (8T) test and theactivated partial thromboplastin time (&8TT) test are dependent upon therea ent system.

1eviewed and 1evised.

basic concepts of hematology (hemostasis)

Documents