BLOOD, BLOOD COMPONENTS ANDBLOOD PRODUCTS

Most blood collected from donors is processed as follows:

■Blood components, such as red cell and plateletconcentrates, fresh frozen plasma (FFP) and cryoprecipitate, are prepared from a single donation ofblood by simple separation methods such ascentrifugation and are transfused without furtherprocessing.

■Blood products, such as coagulation factorconcentrates, albumin and immunoglobulin solutions,

are prepared by complex processes using the plasmafrom many donors as the starting material (UK donor

plasma is not used, see above (

In most circumstances it is preferable to transfuseonly the blood component or product required by thepatient (‘component therapy’) rather than use whole blood.This is the most effective way of using donor blood,

which is a scarce resource, and reduces the risk of complicationsfrom transfusion of unnecessary components of theblood.

Red cell concentratesVirtually all the plasma is removed and is replaced by about

100 mL of an optimal additive solution, such as SAG-M,which contains sodium chloride, adenine, glucose and mannitol.

The mean volume is about 330 mL. The PCV is about0.57 L/L, but the viscosity is low as there are no plasma

proteins in the additive solution, and this allows fast administrationif necessary. All blood components (red cell andplatelet concentrates, and plasma) are leucocyte-depleted inthe UK by filtration within 48 hours of collection of the donorblood.

Washed red cell concentratesThese are preparations of red cells suspended in saline,

produced by cell separators to remove all but traces ofplasma proteins. They are used in patients who have hadsevere recurrent urticarial or anaphylactic reactions

Platelet concentratesThese are prepared either from whole blood by centrifugationor by plateletpheresis of single donors using cell separators.They may be stored for up to 5 days at 22°C with agitation.They are used to treat bleeding in patients with severe thrombocytopenia,and prophylactically to prevent bleeding inpatients with bone marrow failure

Granulocyte concentratesThese are prepared from single donors using cell separatorsand are used for patients with severe neutropenia with definiteevidence of bacterial infection. The numbers of granulocytesare increased by treating donors with G-CSF andsteroids.

Fresh frozen plasmaFFP is prepared by freezing the plasma from 1 unit of bloodat 30°C within 6 hours of donation. The volume is approximately200 mL. FFP contains all the coagulation factorspresent in fresh plasma and is used mostly for replacementof

coagulation factors in acquired coagulation factor deficiencies.It may be further treated by a pathogen-inactivationprocess, e.g. methylene blue or solvent detergent, to minimizethe risk of disease transmission.

CryoprecipitateThis is obtained by allowing the frozen plasma from a singledonation to thaw at 4–8°C and removing the supernatant.The volume is about 20 mL and it is stored at −30°C. Itcontains factor VIII:C, von Willebrand factor (VWF) andfibrinogen, and may be useful in DIC and other conditionswhere the fibrinogen level is very low. It is no longer usedfor the treatment of haemophilia A and von Willebranddisease because of the greater risk of virus transmissioncompared with virus-inactivated coagulation factorconcentrates.

Factor VIII and IX concentratesThese are freeze-dried preparations of specific coagulationfactors prepared from large pools of plasma. They are usedfor treating patients with haemophilia and von Willebranddisease, where recombinant coagulation factor concentratesare unavailable. Recombinant coagulation factor concentrates,where they are available, are the treatment of choicefor patients with inherited coagulation factor deficiencies

AlbuminThere are two preparations:

■Human albumin solution 4.5%, previously called plasmaprotein fraction (PPF), contains 45 g/L albumin and

160 mmol/L sodium. It is available in 50, 100, 250 and500 mL bottles.

■Human albumin solution 20%, previously called ‘saltpoor’albumin, contains approximately 200 g/L albuminand 130 mmol/L sodium and is available in 50 and

100 mL bottles.

Human albumin solutions are generally considered to beinappropriate fluids for acute volume replacement or for thetreatment of shock because they are no more effective inthese situations than synthetic colloid solutions such as polygelatins

)Gelofusine (or hydroxyethyl starch (Haemaccel).However, albumin solutions are indicated for treatment ofacute severe hypoalbuminaemia and as the replacementfluid for plasma exchange. The 20% albumin solution is particularlyuseful for patients with nephrotic syndrome or liverdisease who are fluid overloaded and resistant to diuretics.Albumin solutions should not be used to treat patients withmalnutrition or chronic renal or liver disease with low serumalbumin.

Normal immunoglobulinThis is prepared from normal plasma. It is used in patientswith hypogammaglobulinaemia, to prevent infections, andin patients with, for example, immune thrombocytopenicpurpura

Specific immunoglobulinsThese are obtained from donors with high titres of antibodies.Many preparations are available, such as anti-D, antihepatitisB and anti-varicella zoster

THE WHITE CELL

The five types of leucocytes found in peripheral blood areneutrophils, eosinophils and basophils (which are all calledgranulocytes) and lymphocytes and monocytes

NEUTROPHILSThe earliest morphologically identifiable precursors of neutrophilsin the bone marrow are myeloblasts, which are largecells constituting up to 3.5% of the nucleated cells in themarrow. The nucleus is large and contains 2–5 nucleoli. Thecytoplasm is scanty and contains no granules. Promyelocytesare similar to myeloblasts but have some primarycytoplasmic granules, containing enzymes such asmyeloperoxidase. Myelocytes are smaller cells withoutnucleoli but with more abundant cytoplasm and both primaryand secondary granules. Indentation of the nucleus marksthe change from myelocyte to metamyelocyte. The matureneutrophil is a smaller cell with a nucleus with 2–5 lobes, withpredominantly secondary granules in the cytoplasm whichcontain lysozyme, collagenase and lactoferrin.

Peripheral blood neutrophils are equally distributed into acirculating pool and a marginating pool lying along the endotheliumof blood vessels. In contrast to the prolonged maturationtime of about 10 days for neutrophils in the bonemarrow, their half-life in the peripheral blood is extremelyshort, only 6–8 hours. In response to stimuli (e.g. infection,corticosteroid therapy), neutrophils are released into the circulatingpool from both the marginating pool and the marrow.Immature white cells are released from the marrow when arapid response (within hours) occurs in acute infection

)described as a ‘shift to the left’ on a blood film.(

FunctionThe prime function of neutrophils is to ingest and kill bacteria,fungi and damaged cells. Neutrophils are attracted to sitesof infection or inflammation by chemotaxins. Recognition offoreign or dead material is aided by coating of particles withimmunoglobulin and complement (opsonization) as neutrophilshave Fc and C3b receptors. The material isingested into vacuoles where it is subjected to enzymicdestruction, which is either oxygen-dependent with the generationof hydrogen peroxide (myeloperoxidase) or oxygenindependentoxygenindependent

)lysosomal enzymes and lactoferrin .(Leucocytealkaline phosphatase (LAP) is an enzyme found in leucocytes.It is raised when there is a neutrophilia due to an acuteillness. It is also raised in polycythaemia and myelofibrosisand reduced in CM

Neutrophil leucocytosisA rise in the number of circulating neutrophils to > 10 × 109/Loccurs in bacterial infections or as a result of tissue damage.This may also be seen in pregnancy, during exercise andafter corticosteroid administration. With anytissue necrosis there is a release of various soluble factors,causing a leucocytosis. Interleukin 1 is also released in tissuenecrosis and causes a pyrexia. The pyrexia and leucocytosisaccompanying a myocardial infarction are a good exampleof this and may be wrongly attributed to infection.A leukaemoid reaction (an overproduction of white cells,with many immature cells) may occur in severe infections,tuberculosis, malignant infiltration of the bone marrow andoccasionally after haemorrhage or haemolysis.In leucoerythroblastic anaemia, nucleated red cells andwhite cell precursors are found in the peripheral blood.Causes include marrow infiltration with metastatic carcinoma,myelofibrosis, osteopetrosis, myeloma, lymphoma, and occasionallysevere haemolytic or megaloblastic anaemia

Neutrophil leucocytosis

Tissue necrosis, e.g. myocardial infarction, traumaInflammation, e.g. gout, rheumatoid arthritisDrugs, e.g. corticosteroids, lithiumHaematological:

Myeloproliferative diseaseLeukaemoid reactionLeucoerythroblastic anaemiaPhysiological, e.g. pregnancy, exerciseMalignant disease, e.g. bronchial, breast, gastricMetabolic, e.g. renal failure, acidosisCongenital, e.g. leucocyte adhesion deficiency, hereditaryneutrophilia

Causes of neutropeniaAcquiredViral infectionSevere bacterial infection, e.g. typhoidFelty’s syndromeImmune neutropenia – autoimmune, autoimmune neonatalneutropeniaPancytopenia from any cause, including drug-inducedmarrow aplasiaPure white cell aplasiaInheritedEthnic (neutropenia is common in black races)Kostmann’s syndrome (severe infantile agranulocytosis) dueto mutation in elastane 2 (ELA 2) geneCyclical (genetic mutation in ELA2 gene with neutropeniaevery 2–3 weeks(

Others, e.g. Schwachman–Diamond syndrome, dyskeratosiscongenita, Chédiak–Higashi syndrome

HAEMATOLOGICALMALIGNANCIES

The leukaemias, the lymphomas and multiple myeloma arean interrelated spectrum of malignancies of the myeloid andlymphoid systems. They are uncommon but not rare, thelymphomas alone being the fifth commonest cancer in theUK. The aetiology of these diseases for the most partis unknown, although viruses, irradiation, cytotoxic poisonsand immune suppression have been implicated in a smallproportion of casesThe pathogenesis involvesat least one or usually more molecular abnormalities, andnon-random chromosomal abnormalities have been detectedin several leukaemias and lymphomas. Classification hasbecome increasingly complex, with the universally appliedWHO scheme demanding morphological, cytogenetic andsometimes molecular criteria to be fulfilled. Treatment optionsare multiple

THE LEUKAEMIASThese are relatively uncommon diseases with an incidenceof about 10 per 100 000 per year; which can occur at anyage. They are classified as being acute (short natural history)or chronic (long natural history), and of myeloid or lymphoidorigin. More than half of the leukaemias present acutely (ALL,AML) with the remainder being chronic types (CLL, CML).The type of leukaemia varies with age; acute lymphoblasticleukaemia (ALL) is mainly seen in childhood and chroniclymphocytic leukaemia (CLL) is a disease of the elderly. Themyelodysplastic syndromes are considered pre-leukaemic

.Leukaemia can be diagnosedby examination of a stained slide of peripheral bloodand bone marrow, but immune phenotyping, cytogeneticsand molecular genetics are essential for complete subclassificationand prognostication.

General classificationThe characteristics of leukaemic cells can be assessedby light microscopy, expression of cytosolic enzymes andexpression of surface antigens. These will reflect the lineageand degree of maturity of the leukaemic clone. Thus, leukaemiacan be divided on the basis of the speed of evolutionof the disease into acute or chronic; each of these is thenfurther subdivided into myeloid or lymphoid, according to thecell type involved.

■acute myeloid leukaemia (AML) ■acute lymphoblastic leukaemia (ALL)

■chronic myeloid leukaemia (CML) ■chronic lymphocytic leukaemia (CLL

AetiologyIn the majority of patients this is unknown but several factorshave been associated:

■Radiation. This can induce genetic damage tohaemopoietic precursors and ALL, AML and CML havebeen seen in increased incidences in survivors ofHiroshima and Nagasaki and in patients treated withionizing radiation.

■Chemical and drugs. Exposure to benzene used inindustry may lead to marrow damage. AML occurs aftertreatment with alkylating agents (e.g. melphalan) andtopoisomerase II inhibitors (e.g. etoposide).

■Genetic. Leukaemia risk is highly elevated in a numberof germline conditions that result in genetic instability orbone marrow failure. These include Fanconi anaemia,

ataxia telangiectasia and Li–Fraumeni syndrome. Therisk is elevated some 30 times in people with trisomy21. There is a high degree of concordance amongmonozygotic twins.

■Viruses. Leukaemias are associated with human T celllymphotropic virus type 1 (HTLV-1), which is foundparticularly in Japan and the Caribbean

ACUTE LEUKAEMIASThe acute leukaemias increase in incidence with advancingage. Acute myeloid (myeloblastic, myelogenous) leukaemia

)AML (has a median age at presentation of 65 years and mayarise ‘de novo’ or against a background of myelodysplasia,either of unknown aetiology or related to cytotoxic chemotherapy.Acute lymphoid (lymphoblastic) leukaemia (ALL) hasa substantially lower median age at presentation and in additionis the commonest malignancy in childhood

Clinical featuresThe majority of patients with acute leukaemia, regardless ofsubtype, present with symptoms reflecting inadequate haematopoiesissecondary to leukaemic cells infiltration of thebone marrow:

■anaemia – shortness of breath on effort, excessivetiredness, weakness

■leucopenia – recurrent infections ■thrombocytopenia – bleeding and bruising (particularly

acute promyelocytic leukaemia( ■marrow infiltration – bone pain.

Examination may be unremarkable, but features include: ■pallor

■fever (due to infection, not the disease itself) ■petechiae, purpura, bruises, fundal haemorrhage

)particularly acute promyelocytic leukaemia( ■lymphadenopathy, hepatosplenomegaly (more notable in

lymphoblastic leukaemia( ■violaceous skin lesions (acute myelomonocytic

■testicular enlargement (acute lymphoblastic leukaemia) ■cranial nerve palsies occasionally found (acute

lymphoblastic leukaemialeukaemia(

WHO classification of acute leukaemia

Acute myeloid leukaemiaAML with recurrent genetic abnormalitiesAML with t(8;21)(q22;q22), (AML1/ETO)AML with abnormal bone marrow eosinophils andinv(16)(p13;q22) or t(16;16)(p13;q22), (CBFβ/MYH11)Acute promyelocytic leukaemia with t(15;17)(q22;q12), PML/

RAR-alpha and variantsAML with 11q23 (MLL) abnormalitiesAML with multilineage dysplasiaFollowing MDS or MDS/MDPWithout antecedent MDS or MDS/MDP, but with dysplasiain at least 50% of cells in two or more myeloid lineagesAML and myelodysplastic syndromes, therapy relatedAlkylating agent/radiation-related typeTopoisomerase II inhibitor-related typeOtherAML, not otherwise categorized*

AML, minimally differentiatedAML without maturationAML with maturationAcute myelomonocytic leukaemiaAcute monoblastic/acute monocytic leukaemiaAcute erythroid leukaemia (erythroid/myeloid and pureerythroleukaemia variants(

Acute megakaryoblastic leukaemiaAcute basophilic leukaemiaAcute panmyelosis with myelofibrosisMyeloid sarcoma

Acute lymphoid leukaemia

Precursor B cell acute lymphoblastic leukaemia

t(9;22)(q34;q11); BCR/ABL fusion gene

t(4;11)(q21;q23); MLL-AF4 fusion gene

t(1;19)(q23;p13.3); E2A/PBX1 fusion gene

t(12;21)(p13;q22); TEL/AMLI

Precursor T cell acute lymphoblastic leukaemia

Burkitt-cell leukaemia

InvestigationsConfirmation of diagnosis

■Blood count. Hb low, WBC raised usually (sometimes low), platelets low.

■Blood film. Blast cells almost invariably seen., ,lineage identified morphologically, confirmed with

immunophenotyping. ■Bone marrow aspirate. Increased cellularity,

reduced erythropoiesis, reduced megakaryocytes, sometimestrilineage dysplasia. Replacement by blast cells > 20%