35. Blood Groups and Transfusion Flashcards
Describe the 2 blood group systems used.
What determines blood groups?
What are red cell antigens?
What are antibodies?
Red cell surface as a lipid bilayer with sugar residues and proteins. Sugar residues form ABO blood grouping system. Proteins form the rhesus (Rh) blood grouping system.
Genes
Substanes on red cell surface that can stimulate Ab formation. Over 300 diff so need to define the clinically imp ones.
Immunoglobins in plasma which react specifically with their antigen e.g. anti-A Ab react with A antigen
What are:
a) autoantibodies?
b) alloantibodies?
What is agglutination?
a) react with antigens on person’s own red cells
b) produced by person against antigens not present on their own RBC (naturally occuring, immune)
If an antigen is mixed with its corresponding antibody. (Pic)
Differentiate between IgM and IgG.
What Abs do the following blood groups have in their plasma?
A
B
O
AB
Both naturally occuring antibodies, not born with them. Once born and exposed to environmental antigens, IgM form anti-A or anti-B depending on blood group and activate complement -> punches holes in red cell surface = acute intravascular haemolysis. IgG coat the red cells, and they’re removed by liver/spleen etc. Can get more delayed extravascular haemolysis.
A: anti-b
B: anti-a
O: anti-a and anti-b
AB: no ABO antibody in plasma
What is seen in the
a) Forward ABO grouping tile?
b) Reverse ABO grouping tile?
a) Pt cells mixed with specific antisera at RT. A agglutinated by anti-a, B agglutinated by anti-b, AB agglutinated by anti-a and anti-b, O not agglutinated
b) Pt serum mixed with known red cells at RT. Plasma with anti-b agglutinate B and AB, anti-a will agglutinate A and AB, anti-a and anti-b will agglutinate AB, A and B.
What are the possible genotypes for the following ABO phenotypes:
A
B
AB
O
What blood type would you give to someone if you didn’t know their blood type? Why?
A and B are co-dominant.
A: AA, AO
B: BB, BO
AB: AB
O: OO
NB: More B in asian, more A and O in caucasian
O! They have naturally occuring anti-A and anti-B but very little plasma in transfusion.
What donor blood types can you give for the following pts:
a) O
b) A
c) B
d) AB
a) O
b) A, O
c) B, O
d) AB, A, B, O
What are Rh blood groups?
How do you test for Rh blood groups?
Antigens - 3 pairs inherited as triplet: C or c, D or no D (d), E or e. E.g. RhD+ = have D. These antibodies are immune only - only produced if person exposed to antigen through transfusion, pregnancy or transplantation. About 15% of white caucasion pop RhD- and anti D will be formed if they get transfused with D+ blood or in mum carrying D+ baby b/c dad has D antigen.
NB: Rh+ much more frequent than Rh-
Take red cells with known antigen and combine with known reactant and look. E.g. when combined with C and if + cells go to top. If -ve cells go to bottom. So in pic: heterozgote Cc and homozygote ee, and kell -ve:
What will the following Rh phenotypes be agglutinated by?
1) Antigens CcDe
2) Antigens cdE
1) anti-C, anti-D and anti-E
2) anti-C and anti-E but not by anti-D (b/c no d antigen)
1) If someone has the phenotype CcDEe, what could their genotype combinations be?
2) Phenotype Ccde?
3) Phenotype cde?
1) CDE/cde
CDe/cdE
cDE/Cde
CDe/cDE
2) Cde/cde
3) cde/cde
What is haemolytic disease of the foetus and newborn (HDFN)?
What do all Rh D- mothers all get given now during pregnancy?
Spectrum varies - still-birth, severe brain damage, anaemia and jaundice in newborn. Anti-D is an important common cause. Rh D- mum with first pregnancy carrying Rh D+ child. Immune system sensitised to D antigen. Second RhD+ child - anti D stimulated, crosses placenta and destroys foetal red cells.
Prophylactic anti-D in pregnancy.
For the following patients, what blood would you transfuse?
1) Rh D+
2) Rh D-
What are the 4 different types of blood (red cell) transfusion?
1) RhD+ or RhD-
2) RhD- (RhD+ only to males requiring massive transfusion)
* Avoid giving antigen D to someone who does nothave that antigen*
1) Whole blood - no longer available
2) Red cells - most plasma removed
3) Red cells in additive solution - with most plasma, white cells and platelets removed
4) Leucocyte-depleted red cells - 99% of white cells removed
What conditions may require a red cell transfusion?
What are the risks of transfusion?
Blood loss (surgery, trauma, obstetric haemorrhage), bone marrow failure (leukaemia, cancer), haemolysis (malaria, sepsis), inherited Hb disorders (thalassamia, sickle cell).
Avoid transfusion if anaemia due to Fe, B12 or folate deficiency and gie haematinic replacement therapy instead
Risks: Infection transmission, alloimmunisation that may compromise future transfusion, incompatibile transfusion, circulatory overload, Fe overload
How do you organise a transfusion?
ID, label tube after filling, sign, find Pt’s ABO and RhD type, antibody screen (detects atypical Abs e.g. alloantibodies formed after previous pregnancy or transfusion, and indirect antiglobulin test for IgG Abs).
Can do either physical crossmatching (mix donor red cells and pt serum) or electronic crossmatching (if antibody screening negative).
What happens in the indirect antiglobulin test?
Used to screen for atypical Abs in the pt’s plasma. If prev preg/transfusion, may have IgG Abs = exposing them to delated haemolytic transfusion reaction if go ahead.
Test: pt’s plasma mixed with grp O cells expressing all the common blood group antigens: Rh C c D E e and others. If Ab present it will bind to the antigen on the detector red cells. Positive result = agglutination - Coombs’ test. Then try and ID the antibody with screening.
The pt is monitored closely when undergoing a transfusion. How do you recognise a possible transfusion reaction?
What should be done?
Symptoms: restless, flushing, abdo pain, nausea, diarrhoea
Signs: fever (rapid temp spike >40 degrees), hypertension, haemoglobinguria
STOP TRANSFUSION. Maintain venous access with saline, commence resus. Take blood samples to determine reaction reason inc. direct antiglobulin test.
ABO mismatch can activate complement -> acute intravascular haemolysis, can lead to shock and renal failure.
