Blood groups and transfusions Flashcards
where are the blood groups located on the red cell
Located on the surface of the red cell
what blood group system do sugar residues form
what blood group system to proteins for
Sugar residues form one type of blood group system e.g. ABO - ABO polysaccharide antigens
Proteins form another type of blood group system e.g. Rhesus (Rh)
what determines the blood group
Genes determine what particular sugar or protein is produced and thus the blood group
what are antibodies
- Antibodies are immunoglobulins in plasma which react specifically with their antigens e.g. the anti-A antibody reacts with the A antigen
what are autoantibodies
- Can have autoantibodies – react with antigens present on the persons own red cells
what are alloantibodies
produced by person against antigens not present on persons own red cells
what are the two types of alloantibodies
naturally occurring (exposure to environment)
immune (contact with antigen)
what is agglutination
antibody binds to antigen and clumps stuff together
what antigens are in the ABO system
- A and B polysaccharide antigens
what are the naturally occurring antibodies against the ABO system
- Anti-a
- Anti-b
what are the immune antibodies agains the ABO system
IgM
IgG
what does IgM do
- Cold-acting (bind at room temperature)
- Activate complement
what happens if there is an ABO mismatch transfusion
ABO antibodies can be IgG or IgM, if there is an ABO mismatch transfusion and this will activate haemolysis of red blood cells,
name the blood groups and what antibody they have in there plasma
A (has anti-B in plasma)
B (has anti-A in plasma)
O (has anti-A and anti-B in plasma)
AB (has no ABO antibody in plasma
what will the ABO blood groups be agglutinated by
- Blood of group A will be agglutinated by anti-A
- Blood group B will be agglutinated by anti B
- Blood of group AB will be agglutinated by anti-A and anti-B
- Blood group O will not be agglutinated by anti-a or anti-b
name the phenotypes of the blood groups and what there genotypes could be
A - AA or AO
B - BB or BO
AB - AB
O - OO
for each blood group name
- blood group repent
- antigen present
- antibodies present
- can receive blood groups
Blood group A
- antigen present = A
- antibodies present = B
- can receive blood groups = A and O
Blood group B
- antigen present = B
- antibodies present = A
- can receive blood groups = B and O
Blood group AB
- antigen present = AB
- antibodies present = None
- can receive blood groups = A or B or O
Blood group O
- antigen present = H
- antibodies present = A and B
- can receive blood groups = O
describe the rhesus blood group system
3 pairs of proteins, inherited as triplet:
D or no D (written as d)
C or c
E or e
what can antibodies against rhesus blood groups form
Can form only following exposure:
Transfusion
Pregnancy
Transplantation
describe Rh genotype and phenotype
- Genes are in triplets
- Depending on the phenotype you can try and predict the genotype
- Inherit one triplet from each parent
- Alleles are co-dominant
how can phenotype and genotype of rhesus groups be determined
- Phenotype can be determined serologically
- CcDE red cells will agglutinate with anti-C, anti-c, anti-D, antiE, but not anti-e
genotype can be determined by molecular techniques
if you are RhD positive what blood can you get
if you are RhD negative what blood can you get
RhD positive = RhD positive or RhD negatie
RhD negative = only RhD negative
what happens if you are given the wrong RhD positive or RhD negative in a blood transfusion
- can lead of haemolytic disease of the foetus and newborn
- this is because the mother can form RhD antibodies which cause haemolysis
- leads to fatal anaemia and neonatal jaundice which can cause brain damage
how do you prevent haemolytic disease of the foetus
Prophylaxis after a sensitising event during pregnancy Prophylactic anti-D Ig all D negative mothers in third trimester
Postnatally if baby D positive
Free fetal DNA testing for RHD typing of of fortus from maternal sample now available to help targeted Anti D prophylaxis
what are the blood components and what can they be transfused as
- Red cells for transfusion
- Platelets – low platlet count
- Plasma - uses fresh frozen plasma, cryoprecipitate plasam, fractionation – factor
what are the three different types of plasma that can be used
- fresh frozen plasma
- cryoprecipitate
- fractionation factor concentrates, immunoglobulin, albumin (non UK plasma)
what are the conditions that red blood cells are stored at
Stored at 4 deg C, Shelf life 35 Days,
when should a red cell blood transfusion be sued
Blood loss
- Surgery, Trauma
Obstetric haemorrhage
Bone marrow failure
Leukaemia, cancer, drugs
Haemolysis
Malaria, sepsis, immune, haemolytic disease of newborn
Inherited haemoglobin disorders
Thalassaemia
Sickle cell anaemia
when should you avoid transfusion
Anaemia due to Iron, B12 or folate deficiency
- give haematinic replacement therapy instead.
what are the complications of adverse effects of transfusion
non infectious
immune
• Acute Haemolytic transfusion reaction –ABO incompatible transfusion
• Delayed Haemolytic transfusion reaction
• Febrile non haemolytic
• Allergic - urticatial rash,
anaphylaxis
• Post transfusion purpura
• Transfusion related acute lung injury (TRALI)
• TA-GVHD
non immune
• Fluid overload (TACO)
• Iron overload (in multi-transfused)
infectious • Viral (HBV, HCV, HIV, HepE HTLV, CMV, EBV, parvovirus etc) • Bacterial • Syphilis • Parasites (malaria, trypanosomiasis) • Prions
How do you take blood from a patient
confirm identification by speaking to them (use wrist-band if unconscious)
label tube after filling with blood with full name, date of birth and hospital record number
ensure that no discrepancy between details on bottle and form
sign both form and tube to confirm
what are ABO incompatible transfusions all due to
all due to human error:
Patient wrongly identified (unconscious)
Patient wrongly identified (no wristband)
Patient wrongly identified (human error)
Patient wrongly identified (pre-transfusion sample from wrong patient)
how does an indirect antiglobulin test work
- Patietns serum with IgG
- Incubation with reagent RBC
- Binding to the IgG to reagent RBCs
- Incubation with antibodies to human Ig
- Agglutination (positive indirect coombs test)
what do you do if the antibody screening is negative
Electronic ‘crossmatch’
If antibody screen negative can give ABO and Rh D compatible units without serological crossmatch – strict criteria apply
95% of the blood issued is done this way
how does serological cross matching work
mix donor red cells and patient serum to check compatible
Must do if antibody screen positive or not eligible for electronic ‘crossmatch’
If red cell antibodies then select units negative for those antigens and serologically crossmatch to check compatibility
how do you give a transfusion
- Positively identify the patient by name and DOB and hospital number
- Before transfusing must confirm
o Identity of patient
o Blood group of patient
o Blood group of the unit of blood
Start transfusion
Monitor closely (especially initially)
o Pulse, blood pressure and temperature
what is the possible transfusion reaction
- Restlessness,
- Flushing
- Anxiety
- Abdominal pain
- Nausea
- Diarrhoea
- Abdominal pain
- Pain at venepuncture site
what are the signs of a transfusion reaction
- Fever
- Hypotension
- Haemoglobinguria
what should you do if a transfusion reaction happens
Stop transfusion
- Maintain access with saline commence resuscitation
How do you investigate a transfusion reaction
Take samples for
full blood count, renal and liver function tests
blood cultures,
coagulation screen,
repeat compatibility testing
pre and post transfusion plasma
Direct Antiglobulin Test
assessment of urine for haemoglobin
High dependency management – renal support, DIC
what is a delayed haemolytic transfusion reaction due to
Due to red cell Ab’s - IgG
Rh system/ Kell/ Fya/ Jkb etc
- might have already been exposed in the past therefore IgG is present, If the antibody goes below the point of detection the test might be negative
- then if it is exposed again then you get an delayed haemolytic transfusion reaction
- then the haemoglobin fails to rise and you get jaundice as a by product
when does a delayed haemolytic transfusion reaction happen
7 to 10 days post transfusion
Failure of haemoglobin to rise
Jaundice
what test is used to test to see if a delayed haemolytic transfusion reaction has happened
Direct Antiglobulin Test
how common are delayed haemolytic transfusion reactions
How common are red cell Abs?
~2-5% of transfused patients
Much higher rates allo-immunisation in patients with Sickle Cell Disease ~ 20%
give extended Rh(DCcEe) and K matched blood
how does a direct antiglobulin test work
- RBC with IgG or CS bound to membrane ( already coated with antibodies)
incubation with antibodies to human ig and C3 - Agglutination (positive-direct coombs test)
where do you report transfusion adverse events
SHOT (Serious Hazards of Transfusion)
Collects information on adverse events and feedbacks to hospitals to improve transfusion overall safety
MHRA (Medicines and Healthcare products Regulatory Agency)
- SABRE (Serious Adverse Blood Reactions and Events
