BLOOD TRANSFUSION Blood Transfusion From Donor to Patient - An Overview b y Carl G T du Toit B.Sc. Hons (Biochemistr y) INT RODU CT ION Blood transfusion is defined as the safe transfer of blood c o mp o n e n t s f r o m a d o n o r t o a r e c i p i e n t . D o n a t i n g b l o o d s h o u l d be voluntary an d measures to pro tect donors and recipients s h o u l d b e o f p a r a m o u n t i mp o r t a n c e ( 1 ) . SANBS (South African National Blood Service) is a National organization that provides services related to blood transfusion to eight provinces in South Africa. In a three y ear period S A N B S b l e d 2 . 2 mi l l i o n d o n a t i o n s a n d p r o c u r e d t h e s e donations from a donor base of 680 000 donors. Around 3000 donations are tested daily (2). 1. Crite ria fo r Do nor sel ection Before a potential donor can donate blood , they need to register and co mplete a for m relate d to their general health and medi cal hi story . The form al so i ncl udes questi ons rel ati ng to a n y b e h a v i o u r wh i c h c o u l d i n c r e a s e t h e r i s k o f t r a n s m i t t i n g disease to the recipient. T h e p r i ma r y o b je c t i v e o f D o n o r s e l e c t i o n i s t h e r e f o r e d e s i g n e d a r o u n d t wo t h e m e s : 1. The safety of the donor. 2. A quality blood product that is safe for t h e r e c ip ie n t . Specific steps, to ensure that blood transfusion is safe , are t a k e n a n d i n c l u d e t h e f o l l o wi n g : -1- Carl G T du Toit BLOOD TRANSFUSION 1 . V o l u n t a r y , n o n - r e mu n e r a t e d ( u n p a i d ) d o n a t i o n s h a v e b e e n s h o wn t o b e t h e b e s t w a y t o r e c r u i t s a f e d o n o r s . 2. Questions are posed to donors about their general health. 3 . T h e me d i c a l h i s t o r i e s o f d o n o r s a r e o b t a i n e d b y a q u a l i f i e d n u r s i n g s i s t e r o r p h l e b o t o mi s t . 4 . A o n e - o n - o n e i n t e r v i e w i s c o n d u c t e d wi t h t h e d o n o r . 5 . A p h y s i c a l e xa mi n a t i o n i s c o n d u c t e d p r i o r t o d o n a t i o n . 6. Laboratory testing is conducted on all donations. 7. The donor‟s identity is checked against a deferral registry. 8. Providing a method b y which the donor can indicate the unit as unsuitable for transfusio n (3). F o r t h e i r o wn p r o t e c t i o n , d o n o r s a r e r e q u i r e d t o c o mp l y wi t h t h e f o l l o wi n g c r i t e r i a : A g e : O l d e r t h a n 1 6 y e a r s , a n d f i r s t t i me d o n o r s n o t older than 65 years. W ei ght: > 50kg (dependi ng on the h ei ght of the donor) H a e mo g l o b i n : > 1 2 . 5 g / d l Pulse rate of 50 - 100 beats per min ute. Blood pressure between 100/60 and 180/100. M i n i mu m d o n a t i o n i n t e r v a l o f 8 we e k s ( 1 2 - 1 6 we e k s advised) P r e g n a n t a n d l a c t a t i n g wo m e n a r e e xc l u d e d b e c a u s e o f h i g h i r o n r e q u i r e me n t s . E xc l u s i o n s o f p e r s o n s wi t h : - Cardiovascular disease, including hypertension - Significant respiratory disorders - Epilepsy and other CNS disorders - D i a b e t e s me l l i t u s - Chronic renal disease - O n g o i n g me d i c a l i n v e s t i g a t i o n s / c l i n i c a l t r i a l s E xc l u s i o n o f a n y d o n o r r e t u r n i n g t o o c c u p a t i o n s s u c h a s d r i v i n g a b u s , p l a n e o r t r a i n , h e a v y ma c h i n e operator, etc. because possible delayed fainting could be dangerous. Donors are also deferred if they are going to u n d e r t a k e a l o n g p l a n e jo u r n e y o n t h e d a y t h e y wi s h to donate blood (6). -2- Carl G T du Toit BLOOD TRANSFUSION 1.1 T h e S AN B S ( S o u t h A f r i c a n N a t i o n a l B l o o d S e r v i c e ) Compre he nsi ve Dono r Q uestio nna ire T h e D o n o r Q u e s t i o n n a i r e c o n s i s t s o f f o u r p a g e s wi t h t h r e e parts. The first page of the Donor For m c onsists of the de mographics of the donor and an i mportant no tice r egarding HIV. Sou th Africa has a high incidence of HIV and potential donors are strongly advised against donating blood if they suspect they may ha ve been e xposed to HI V/AI DS. • Part one of the Health Questionnaire consists of a n s we r i n g h e a l t h q u e s t i o n s r e l a t i n g t o t h e me d i c a l h i s t o r y o f t h e d o n o r . S o me o f t h e q u e s t i o n s a r e d e s i g n e d f o r t h e protection of the donor , while others are specific to the protecti on of the reci pi ent. The questi ons are about general h e a l t h , me d i c a t i o n , r e s e n t o r p a s t s u r g e r y , r e s e n t o r p a s t infections and/or conditions or disorders that could preclude the donor from donating. The questionnaire states u n e q u i v o c a l l y t h a t a l l a n s we r s wi l l b e t r e a t e d c o n f i d e n t i a l l y . • T h e s e c o n d p a r t ( S e l f - e xc l u s i o n q u e s t i o n n a i r e ) c o n s i s t s o f questi ons rel ati ng to li festyl e and any behavi or that coul d i n c r e a s e t h e r i s k o f t r a n s mi t t i n g H I V t o t h e p a t i e n t . T h i s p a r t i n c l u d e s d i r e c t q u e s t i o n s a b o u t t h e s e xu a l b e h a v i o r o f t h e d o n o r a n d i s d e s i g n e d t o i d e n t i f y p o s s i b l e wi n d o w p e r i o d donations. T h e q u e s t i o n s a d d r e s s t h e f o l l o wi n g : S e xu a l p r o mi s c u i t y v s . a s i n g l e , r e g u l a r s e x p a r t n e r P r o t e c t e d s e x - i . e . s e x wi t h a c o n d o m Male donor sa me se x partners Prostitution This section also evaluates the risk relating to the use of a surgi cal needl e to take narcoti cs, steroi ds or any substance not p r e s c r i b e d b y a d o c t o r o r a n u r s e . T h e s e l f - e xc l u s i o n q u e s t i o n n a i r e i s l e g a l l y b i n d i n g a n d a i ms t o i d e n t i f y p o s s i b l e wi n d o w p e r i o d d o n a t i o n s a n d e x c l u d e t h e m. • T h e t h i r d p a r t ( D e c l a r a t i o n ) i s a f o r ma l s t a t e m e n t wh e r e the potential donor confirms that he or she understands the q u e s t i o n s a n d h a s a n s we r e d a l l t h e q u e s t i o n s a c c u r a t e l y a n d h o n e s t l y . T h i s h a s l e g a l i mp l i c a t i o n s a n d i s i mp o r t a n t wi t h respect to the code of ethi cs for bl ood donati on and t r a n s f u s i o n . T h e c o n c e p t o f t r u s t i s mo s t i mp o r t a n t , wi t h c o n f i d e n t i a l i t y a n d i n f o r me d c o n s e n t s e r v i n g a s t h e c o r n e r s t o n e of the donating process (3). • The last page of the questionnaire, (For office use), is for a d mi n i s t r a t i o n r e l a t e d i s s u e s a n d i s c o mp l e t e d b y a s t a f f m e m b e r t o r e c o r d t h e p h y s i c a l e xa m i n a t i o n o f t h e d o n o r . -3- Carl G T du Toit BLOOD TRANSFUSION D o n o r s e l e c t i o n , d e f e r r a l a n d / o r e xc l u s i o n a r e s p e c i f i c a l l y designed to protect the health of the donor and to prevent the t r a n s mi s s i o n o f d i s e a s e s t o t h e r e c i p i e n t - t h a t i s , t h e r i s k t o r e c i p i e n t i s mi n i mi z e d . N e v e r t h e l e s s , a l l d o n a t e d b l o o d s t i l l need to be tested to guarantee that the blood is indeed safe for the recipient. 2. Donatio n testi ng A s a l r e a d y me n t i o n e d b l o o d ma y t r a n s mi t i n f e c t i o u s d i s e a s e s . Blood and blood products are therefore routinely tes ted for markers of trans missible diseases. All donated blood i s tested according to the standards of practice of Blood Transfusion in South Africa (4). It is standard practice in South Africa to test every single unit of donated blood (5). Bl ood uni ts are coll ected by an asepti c techni que i nto pl asti c b a g s c o n t a i n i n g a n a p p r o p r i a t e a mo u n t o f a d d i t i v e s o l u t i o n e . g . AdSol . Uni ts are then sent to bl ood transfusi on l aboratori es for p r o c e s s i n g . A t t h e t i me o f d o n a t i o n s p e c i me n s a r e a l s o collected for laboratory testing. Every unit collected from a donor i s acco mpanied by three blo od sa mples for m that donor . O n e s a mp l e f o r A B O b l o o d g r o u p i n g , o n e f o r s e r o l o g y t e s t i n g and one for N AT (Nucl ei c Aci d A mpl i fi cati on Testi ng) . Tests are perfor med b y trained and qualif ied laboratory t e c h n i c i a n s a n d t e c h n o l o g i s t s o n a u t o ma t e d a n a l y z e r s . The application and use of automation for all aspects of c o mp a t i b i l i t y t e s t i n g h a s i n c r e a s e d s e c u r i t y o v e r ma n u a l testing. Tests are done for mainly for: ABO and D grouping Hepatitis viruses - Hepatitis B virus (Hepatitis B surface antigen HBsAg) - Hepatitis C virus (HCV) Retroviruses - H u ma n i m m u n o d e f i c i e n c y v i r u s ( H I V ) 1 a n d 2 Bacteria - T r e p o n e m a p a l l id u m ( s y p h i l i s ) South Africa has a high prevalence of HIV; therefore there i s a h i g h r i s k o f t r a n s mi t t i n g t h e d i s e a s e b y b l o o d t r a n s f u s i o n , e v e n though the tested blood may be found negative for these m a r k e r s . T h i s i s d u e t o t h e wi n d o w p e r i o d , wh i c h r e f e r s t o t h e -4- Carl G T du Toit BLOOD TRANSFUSION t i me w h e n a p e r s o n i s f i r s t i n f e ct e d u n t i l t h e p e r s o n t e s t s p o s i t i v e . D u r i n g t h e wi n d o w p e r i o d , wh i c h ma y l a s t f o r mo n t h s , the laboratory tests may be negat ive but the person is still c a p a b l e o f i n f e c t i n g o t h e r s . I t i s t h e r e f o r e o f t h e u t mo s t i mp o r t a n c e t h a t t h e a n s we r s g i v e n i n t h e D o n o r Q u e s t i o n n a i r e by the potential d onor is accurate a nd honest. „ W it h t h e in t r o d u c t io n o f N u c l e ic a c id t e s t in g ( N A T ) in 2 0 0 5 , t h e w in d o w p e r io d h a s b e e n r e d u c e d t o 1 1 d a y s . C u r r e n t l y t h e c a l c u l a t e d r e s id u a l r i s k o v e r a l l ( u s i n g a n in f e c t io u s d o s e o f 1 0 c o p ie s ) i s 6 p e r m i l l i o n d o n a t io n s . S in c e t h e im p l e m e n t a t io n o f I n d iv id u a l D o n a t io n N u c l e i c a c i d t e s t in g ( I D - N A T ) t h e r e h a v e b e e n n o r e p o r t e d c a s e s o f H I V t r a n s f u s io n t r a n s m i s s i o n . ’ ( 2 ) I t i s i mp o r t a n t t o n o t e t h a t t h e s c r e e n i n g t e s t s a r e n o t d i a g n o s t i c a n d f a l s e p o s i t i v e r e s u l t s ma y b e o b t a i n e d . D o n o r s a r e i n f o r me d a n d o f f e r e d c o u n s e l i n g i f a n y r e s u l t s a r e p o s i t i v e . D o n o r s t h e n h a v e t h e o p t i o n t o c o n f i r m t h e s e r e s u l t s wi t h t h e i r doctor or at their clinic. 3. Compone nt t he rapy H i s t o r i c a l l y , b l o o d wa s t r a n s f u s e d a s wh o l e b l o o d wi t h o u t a n y processi ng. W hol e Bl ood i s no l onger routi nel y used because t h e e xt r a p l a s m a c a n c o n t r i b u t e t o t r a n s f u s i o n a s s o c i a t e d circulatory overload (TACO), a potentially dangerous c o mp l i c a t i o n . The selective transfusion of suitable blood products has b e c o me r o u t i n e b e c a u s e t h e a p p r o p r i a t e c o mp o n e n t t h a t i s b e s t sui ted to correct a pati ent defi ci ency can no w be chosen and transfused in concentrated for m. Using red cell concentrated, f o r e xa m p l e , mi n i mi z e s t h e p o s s i b i l i t y o f c i r c u l a t o r y o v e r l o a d and cardiovascular failure (1). T h r e e c o mp o n e n t s a r e ma d e b y t h e i n i t i a l c e n t r i f u g a t i o n o f wh o l e b l o o d : r e d c e l l s , b u f f y c o a t a n d p l a s ma . ( F i g . 1 ) -5- Carl G T du Toit BLOOD TRANSFUSION Fig. 1: T he preparatio n o f b lo od co mpo nent s fro m wh o le b loo d. (1) → *FFP for clinical use → *FFP for fractionation → - Albumin - Gamma globulin → Fresh plasma Whole blood - Coagulation Factors → Cryoprecipitate + cryosupernatant → Platelets → Buffy coat → Red cell concentrate * F F P = f r e s h f r o z e n p l a s ma According to the SANBS “Request for blood or blood c o mp o n e n t s ” F o r m, t h e f o l l o wi n g b l o o d p r o d u c t s a r e a v a i l a b l e and the storage conditions, stability and usage of these products are su mmarized in Table 1. Table 1 Blood products storage, stability and Indications Blood products Storage Stability Red cell concentrate 2-6°C 35 days Red cell concentrate (Leucodepleted) 2-6°C 24 hrs 20-24°C with agitation 5 days 20-24°C 6 hrs Platelet concentrate (Pooled) -6- Indications - Correction of red cell deficiencies (Anemias) - Massive blood loss - Multiple transfused patients - Babies - Leukaemia and lymphoma Carl G T du Toit BLOOD TRANSFUSION with agitation (Single Donor) Cryoprecipitate o n c e t h a w e d a t 3 7 °C Plasma (Fresh frozen) - Severe thrombocytopaenia - Chemotherapy - Bone marrow transplantations - Bleeding - DIC (Disseminated intravascular coagulation) 20-24°C with agitation -18°C 5 days 20-24°C 4 hrs -18°C 1 year 1 year - Long term platelet therapy e.g. leukaemia Haemophilia - Replacement of clotting factor deficiencies - Reversal of Wafarin effect - Massive blood transfusions - Used in antithrombin III deficiencies - Treatment of immunodeficiencies 4. Compatibilit y T esting C o mp a t i b i l i t y t e s t i n g c o n s i s t s o f : Checking to ensure the correct sample is used. - Pati ent detai l s on th e req ue st f orm m ust m atch the details on the blood sample. . Checking the records for previous group/antibody detection. ABO and Rh grouping. - F or ward an d rev erse gr ou pi ng i s perf or m ed. - Veri f y groupi ng re sul ts a gai n st pr ev i ous resul ts. An antibody screen. - If the anti body sc ree n i s n eg ativ e an imm edi ate spi n cr o ss-m atch i s p erf orm ed. - If the scr een i s p o si tiv e the anti body must be i de nti fi ed so the appropriate blood can be selected. Selecting appropriate blood for transfusion. C r o s s - m a t c h i n g t h e p a t i e n t ‟ s s e r u m o r p l a s ma against the donor‟s red cells. - If there i s n o hi story of anti bodi e s and no anti b odi e s ar e detecte d an i m m edi ate spi n cro ss -m atch i s p erf orm ed. - If anti bodi e s ar e det ected an i ndi rect a nti gl obul i n test s (IAT) cross-m atch i s u se d. - If the re sul t i s po si tiv e the bl ood i s i nco m pati bl e and cannot be used. Visual inspection of red cell units. - Bef ore a uni t i s i ssue d f or transf u si on i t sh oul d b e i nsp ecte d f or l eakage, ev i dence of heam ol ysi s, di scol or ati on and p re sence of cl ots. - I f any of t hese are o b serv ed t he u ni t m ust n ot be u sed. -7- Carl G T du Toit BLOOD TRANSFUSION I n a n e m e r g e n c y s i t u a t i o n t h e r e m a y n o t b e e n o u g h t i me t o perform all these tests. The result from the ABO and Rh typing is used to issue blood and the antibody screen and indirect a n t i g l o b u l i n t e s t ( I A T ) mu s t b e p e r f o r me d a f t e r w a r d s . 5. Haza rds Of T ransf usio n Transfusion reactions are any adverse events that occur because of blood transfusion. Safe and effective blood transfusion therefore requires the co mbined efforts o f blood transfusion services, technicians, technologists, scientists and cl i ni ci ans to ensure the hi ghest standards are appli ed to al l syste ms in the co mple x proce ss fro m donor to patient. T h e mo s t c o m m o n c a u s e o f i s s u i n g t h e i n c o r r e c t b l o o d c o mp o n e n t i s e i t h e r c l e r i c a l , a d mi n i s t r a t i v e o r t r a n s c r i p t i o n e r r o r s . E r r o r s c a n o c c u r a t t h e p o i n t o f l a b e l i n g o f b l o o d ( wr o n g l a b e l o n wr o n g t u b e ) , l a b o r a t o r y t e s t i n g ( t e c h n i c a l e r r o r ) , b l o o d u n i t l a b e l i n g ( a d mi n i s t r a t i v e e r r o r ) a n d c o l l e c t i o n f r o m t h e blood refrigerator or inadequate bedside checking. In 1996 the “ Serious Hazard of Tr ansfusion” (SHOT) s che me wa s i n t r o d u c e d . T h i s c o n f i d e n t i a l r e p o r t i n g s c h e me , u s i n g detai l ed anal ysi s of errors, has pr ovi ded data that have enabled both national bodies and local transfusion services to i n t r o d u c e me a s u r e s t o r e d u c e r i s k ( 5 ) . Acute life-threatening transfusion reactions can result from the f o l l o wi n g : 1. Acute hae molytic reactions: - Acute i ntrav ascul ar h eam ol ysi s a s the r esul t of ABO incompatibility. - Sev ere ex t rav ascul ar h eam ol ysi s h app e ns whe n a stro ng anti bo dy i s m i ssed i n pr e -tra n sf usi on te sti ng and c au se s rapi d cl e aran ce of i n com pati bl e red cel l s. 2 . A n a p h y l a xi s a n d s e v e r e a c u t e a l l e r g i c r e a c t i o n s - a r e associ at e d wi t h pl a sm a wher e t he r eci pi ent ha s b een pre se n si ti zed to an al l erge n i n the do nor pl a sm a. 3. Transfusion of an infected blood product - this i s more comm on wi t h pl at el et s a s t hey are st or ed at room t em perat ure. 4 . T r a n s f u s i o n - a s s o c i a t e d a c u t e l u n g i n ju r y ( T R A L I ) - t h i s i s cau se d by th e pre senc e of anti -l eukocyte anti bodi e s th at cau se leucocytes to aggregate and become trapped in the pulmonary circulation. 5 . D e l a y e d h a e mo l y t i c t r a n s f u s i o n r e a c t i o n s . 6. Transfusion related graft vs. ho st disease. -8- Carl G T du Toit BLOOD TRANSFUSION 7. Post- transfusion purpura. T r a n s f u s i o n r e a c t i o n s c a n b e a cu t e ( wi t h i n 2 4 h o u r s ) o r d e l a y e d ( a f t e r t wo o r m o r e d a y s ) . I f a n a c u t e t r a n s f u s i o n r e a c t i o n i s s u s p e c t e d , p r o mp t a c t i o n t o s t o p t h e t r a n s f u s i o n i s e s s e n t i a l t o s e c u r e a b e t t e r o u t c o m e . T h e l a b o r a t o r y mu s t b e i n f o r me d i m m e d i a t e l y . T h e u n i t o f b l o o d , a s we l l a s b l o o d a n d u r i n e s a mp l e s ( p o s t t r a n s f u s i o n s a mp l e s ) f r o m t h e p a t i e n t s , m u s t b e r e t u r n e d t o t h e l a b o r a t o r y a s t h e y wi l l i n v e s t i g a t e t h e cause. I mmediate investigations in the cas e o f an acute transfusion r e a c t i o n i n c l u d e t h e f o l l o wi n g s t e p s : Check for heamolysis - Vi sual i n sp ecti on of pl asm a an d uri ne . - Bi li rubi n and LDH l ev el s wi l l be rai sed . C h e c k f o r i n c o m p a t i b il i t y - Check the patient‟s identity and related documentation. - Rep eat ABO gro upi ng, a nti bodi e s scr ee n and c ro ssm atch on bot h the p re - a nd p o st tran sf u si on sa m pl es. - Perf orm di rect anti gl obul i n test (DAT) o n pati ent. Check for DIC - Perf orm blood count and coagulation screen. Check renal function - Check bl ood ure a, cr eati ni ne a nd el ectr ol ytes. C h e c k f o r b a c t e r ia l in f e c t io n s - Take blood cultures f rom the patient and donor unit. P e r f o r m im m u n o l o g i c a l in v e s t ig a t i o n s - Check IgA l ev el s and anti -IgA anti bo di e s. Since the introduction of the SHOT ( Serious Hazard of Transfusion) sche me it ha s be co me clear that multiple errors can occur. The annual reports make reco mmendations for i mp r o v i n g a n d a p p l y i n g s t r i c t p r o t o c o l s f o r s a m p l e l a b e l i n g a n d t e s t i n g , l a b o r a t o r y p r o c e d u r e s , r e l i a b l e d o c u me n t a t i o n , a n d frequent staff training. 6. Qualit y Ass ura nce in Blood T rans fusion Laboratories Q u a l i t y a s s u r a n c e i s a v e r y i mp o r t a n t a s p e c t o f t h e b l o o d t r a n s f u s i o n p r o c e s s a n d a i m s t o e n s u r e t h a t t h e p a t i e n t wi l l receive sufficient, safe, quality blood products. A l aboratory needs to b e accredi ted. An authori tati ve body l i ke the South African National Accreditation Syste m ( SANAS) mus t g i v e f o r ma l r e c o g n i t i o n t h a t a n o r g a n i z a t i o n i s c o m p e t e n t t o carry out specific tasks. -9- Carl G T du Toit BLOOD TRANSFUSION Should there be any deviation from the policies or standard operating procedures of the Blood Transfusion service these n o n - c o n f o r ma n c e s m u s t b e i n v e s t i g a t e d a n d r e s o l v e d . N o n c o n f o r ma n c e s m u s t b e u s e d t o t a k e p r e v e n t a t i v e a c t i o n a n d t h u s c o n t i n u o u s l y i mp r o v i n g t h e e n t i r e s y s t e m . 7. Objections to blood tra nsfus ion O b je c t i o n s t o b l o o d t r a n s f u s i o n s ma y a r i s e f o r p e r s o n a l , m e d i c a l , o r r e l i g i o u s r e a s o n s . F o r e xa m p l e , J e h o v a h ' s W i t n e s s e s o b je c t t o b l o o d t r a n s f u s i o n p r i ma r i l y o n r e l i g i o u s grounds. If the patients‟ life could be saved by vital transfusion but the pati ent or thei r parent s or legal guardi an s (i n the case o f a c h i l d ) r e f u s e t r a n s f u s i o n , t h e c o u r t s ma y b e c a l l e d u p o n t o intervene. Judges tend to rule in favour of transfusion (8). REFERENCES 1. Hoffbrand A.V., Moss P.A.H., et al. 2006. Essential Haematology. 5th edition. Blackwell Publishing, Oxford. (Chapter 27 - Blood transfusion) 2. Vermeulen M., Sykes W., Gaggia L., et al. 10 September 2009. Impact of Individual Donation Nucleic Acid Testing (ID-NAT) on the Residual HIV Transmission Risk of South African Blood Transfusions: Three Year Experience. [PowerPoint presentation] 3. Smalberger. H. April 2010. Why you have to complete the Donor Questionnaire. BloodBeat Volume 3 (Issue 3): 10-11. 4. Hendrickse H. 2010. Lecture Notes - Blood Transfusion II. Cape Peninsula University of Technology. 5. South African National Blood Service. 2009. Are you giving blood for the right reasons? [Pamphlet] 6. Lewis S. M., Bain B. J., Bates I., et al. 2006. Practical Haematology. 10th edition. Elsevier, Philadelphia. (Chapter 20 - Laboratory aspects of blood transfusion) 7. South African National Blood Service. 2009. Be a Platelet Donor. [Pamphlet] - 10 - Carl G T du Toit BLOOD TRANSFUSION 8. Longmore M., et al. 2007. Oxford Handbook of clinical Medicine. 7th edition. Oxford University Press, New York. - 11 - Carl G T du Toit