introduction to clinical hematology

INTRODUCTION TO CLINICAL HEMATOLOGYVet . Heba Yasser

BLOOD

Blood is the biological fluid most routinely analyzed in the laboratory.

BLOOD

Blood is a fluid tissue that circulates through the vascular channels carrying the necessities for life to all cells of the body, and it receives the waste products of metabolism for transport to the organs of excretion.

BLOOD COMPOSITION

The cellular portion

is assessed in the clinical hematology laboratory

The liquid portion

evaluated in the clinical

biochemistry laboratory.

AIM OF BLOOD EXAMINATION:

1. Screening procedure for general health.

2. Diagnosis of different diseases.3. To asses the body's ability to fight

infection (cellular immunity).4. Evaluation of certain disease

condition.5. Follow up the response to certain

therapy.

PHYSIOLOGICAL CONSIDERATIONS IN INTERPRETATION OF BLOOD VALUES

1. Emotional stress: facing different environment in the veterinary clinic, Blood should be collected when the animal is at rest.

2. Exercise: especially in animals which have a responsive spleen, like horse.

PHYSIOLOGICAL CONSIDERATIONS IN INTERPRETATION OF BLOOD VALUES

3. Diet: Samples shouldn't be collected soon or shortly after feeding. Animal is preferred to be fasted(8-10 hours) before sampling to avoid processing problems associated with postprandial lipemia.

4. Drugs5. Age, sex and breed

Physiological response

function Altered test

Emotional stress:

Epinephrine Hyperglycemia LecucytosisLymphocytosis in cats

Blood sugar testT.L.C.D.L.C

Exercise: Hypoxia induce spleenic contraction

Release of blood cells into circulation

PCVTLC

Prolonged exercise:

increases activity of muscular enzymes

CK, AST, LDH

Diet: after meals

lipemic Blood sugar testLipids test

Starvation:

Decreased BUN &serum albumin

Drugs: Glucocorticoids Liver enz.

Activity

TLC, DLC,BUN ALP, ALT

alter tests to detect immune-mediated diseases.

Physiological response

function Altered test

Drugs:exogenous insulin

decreases serum glucose

Blood glucose test and serum potassium

Antibiotics :Cephalosporins

increased creatinine concentration

Age, sex and breed

Significantly influences some of the blood values.

COLLECTION AND HANDLING THE BLOOD SPECIMEN

The selection of the proper container and the proper anticoagulant must be made prior to specimen collection.

1. Containers (equipment): Syringes and Vaccutainers

Are of variable sizes. Should be chemically clean and dry. Glass vials fitted with rubber or polyethylene

stoppers are recommended.

2. Anticoagulants 

SYRINGES : PRECAUTIONS

The blood must be transferred quickly into the anticoagulant to prevent initiation of the clotting mechanism.

Using calibrated syringe to ensure the collection of an exact volume of blood suitable to the amount of the anticoagulant contained in the sample vial.

Old metallic syringe

Plastic disposable syringe

VACUTAINERS (VACUUM TUBES)

Are plain, anticoagulated or containing clotting accelerator.

The stoppers' color indicates the contained anticoagulant and use.

TECHNIQUE AND PRECAUTIONS OF BLOOD COLLECTION

I. Precautions before blood collection:

1. Select the site of sampling; free from cyanosis, inflammation, or edema.

2. Shave the site of sampling; especially in long-haired animals.

3. Sterilize the site of sampling by 70 % alcohol. (Rubbing with alcohol makes the vein more clearly outlined).

4. Anesthesia and skin incision may be required; in the rat, guinea pig, and rabbit.

II. AMOUNT OF BLOOD REQUIRED:

Depends on the requested test(s), and the method used for conducting the test.

As a general role; it is usually safe to take about 0.5 ml blood/kg body weight in all species.

5 ml in large animals and 2 ml of blood in small animals are sufficient for routine blood study.

1. SMALL AMOUNT OF BLOOD:

Site: Capillary bed of the skin, Clipping the toe nail, or Bricking the marginal ear vein. Aim:Small amount of blood is collected if only RBCs

count, hemoglobin concentration, PCV, leucocytes count, or blood smear examinations are needed.

Technique:Sudden sharp stab using an automatic lancet, an

ordinary lancet, or sterile needle.Exclude the first exuding blood drop (contaminated

with the tissues) and collect the second. 

Lancets

2. LARGE AMOUNT OF BLOOD

Large blood samples are drown from major veins.

Occlude the vein using digital pressure or tourniquet.

Stretch the skin across the vein. Insert the needle, while the bevel is

directed upward.Apply gentile traction or suction of blood to

avoid collapse of the vein.Release the digital pressure, or remove the

tourniquet. Gently withdraw the blood by the plungers.

Jugular vein

SITES OF BLOOD COLLECTION

Horse, Sheep, Goat and Camel: Jugular vein (middle third; more superficially

exposed). Cow: Jugular vein (middle third; more superficially

exposed), Tail venipuncture (coccygeal vein), or the mammary vein.

Dog:Cephalic (most commonly), jugular (occasionally),

saphenous, or tibial veins. Cat:Cephalic (most commonly), jugular (occasionally),

or femoral veins, or clipping of the toe nail.

Sampling from cephalic vein in cats

Jugular vein in dog

Sampling from coccogyeal artery in cow

Jugular vein in lamb

Jugular vein in horse

SITES OF BLOOD COLLECTION

Rabbit, Guinea pig: Heart, ear vein, or jugular vein (occasionally). Pig: Anterior vena cava, ear vein, or jugular vein

(occasionally). Rat, Mouse:Tail amputation (the commonest), retro orbital

venous plexus, or the heart. Birds: Wing vein, cutaneous ulnar vein, or brachial

veins, or the heart.

Ear vein in rabbit

Wing vein in bird

Sampling in mice

HANDLING OF THE COLLECTED BLOOD SAMPLE

Blood samples should be processed as soon as possible after collection.

On standing; the cells settle down and separate from the plasma,

so it is necessary to mix the sample thoroughly each time a portion is removed for a test.

HANDLING OF THE COLLECTED BLOOD SAMPLE

The blood film is best made immediately from fresh blood, 15 minute.

OR as soon as possible from anticoagulated blood, preferably within an hour of sampling, as WBCs undergo degenerative changes due to aging of the cells.

HANDLING OF THE COLLECTED BLOOD SAMPLE

Blood can be kept at room temperature for 1-2 hours.

If blood examination is to be postponed for several hours or overnight; make blood films immediately, perform ESR, and then refrigerate the sample. The cell remains stable at 4o C for 24 hours.

An ice box or cold packs should be used to transport blood samples to a distant laboratory.

IDENTIFICATION OF THE COLLECTED BLOOD SAMPLE  Specimens to be sent to the laboratory

should be completely identified. A complete history should be included with

each sample.

ANTICOAGULANTS

Hematological examination requires blood in liquid form.

Immediately after withdrawal; blood must be thoroughly mixed with the anticoagulant to prevent clotting.

The common used Anticoagulants are: Heparin, EDTA, Sodium fluoride, Sodium citrate and double oxalates.

Mode of action

Dose Recommended uses

Advantages Disadvantages

Heparine

EDTA

Sod.Citrate

Sod.flouride

Double oxalate

CAUSES OF SPECIMEN SPOILAGE

1. Hemolysis: Breakdown of the cellular elements of the blood.

Effect of hemolysis on lab. Results:Hemolysis interferes with the laboratory investigations which are measured colorimetrically; either by:

a) changing the optical density b)releasing intracellular components. causing

false increase or decrease in the concentration of the analytes

CAUSES OF HEMOLYSIS

A) Before withdrawal: Using wet syringe or needle. Using needle of small gauge.

B) During withdrawal: Rapid withdrawal of the blood. Moving the needle inside the vein. Placing the blood into the vacuum tubes too

quickly.

C) After withdrawal:

o Dispensing the blood without removing the needle.

o Incorrect dose of the anticoagulant.o Vigorous mixing of the blood with the

anticoagulant.(Rough handling of specimen).o Centrifuging blood for longer time and at higher

speed.o Exposing blood to extreme heat or cold.o Storing whole blood samples in freezing

temperature.o Bacterial or chemical contamination.

CAUSES OF SPECIMEN SPOILAGE

2. Lipemia: The presence of high concentration of lipids in the blood.

Effects of lipemia on laboratory tests: Lipemia enhances hemolysis. Lipemia produce false-high values of Hb, and

so incorrect MCH and MCHC. Turbidity of the serum impair end-point

spectrophotometric determinations.

LIPEMIA

Lipemia falsely decrease serum sodium and potassium measurements by flame photometry.

Lipemia falsely increase plasma proteins measurement by refracto- metry.

Lipemia causes false decrease in cholesterol in cats.

CAUSES OF SPECIMEN SPOILAGE

3. Clotting: The blood loses its liquid form and becomes clotted.

Causes of clotting: Taking too much time in obtaining the blood;

so the blood has already started to clot before being mixed with the anticoagulant.

Using no anticoagulant. Failure to mix the blood with the

anticoagulant. Using inadequate dose of the anticoagulant. 

CAUSES OF SPECIMEN SPOILAGE

4. Decomposition: due to overgrowth of bacteria or mould. The blood become unfit for examination.

Causes of decomposition: High temperature. Bacterial contamination. Contamination with the soil or fecal

materials. 

CAUSES OF SPECIMEN SPOILAGE

5. Desiccation (Drying):Drying of blood sample.

Causes of sample drying: Failure to back the specimen properly. The principal packing faults are: a) too small sample in a too large container.

b) leaving the container opened to air.