blood groups and transfusions Flashcards
where are blood groups found?
on the surface of RBCs
what is the ABO blood group made of?
sugar residues
what is he Rh blood group made of?
proteins
what determines the blood group?
genes
what are antibodies
immunoglobulins in plasma which react specifically with their antigen
what are autoantibodies?
react with antigens present on person’s own RBCs
what are alloantibodies? what types are there?
produced by the person against antigens not present on their own RBCs
- Naturally occurring (exposure to environment)
- Immune (contact with antigen)
at what temperature does IgM bind?
room emp
what does IgM do?
activates complement
name the ABO blood groups and their antibodies
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 is the ABO phenotype?
antigens detectable on RBC membrane
what is the ABO genotype?
antigens encoded in DNA (one copy from each parent)
what are the possible genotypes for blood group A?
AA, AO
what are the possible genotypes for blood group B?
BB, BO
what are the possible genotypes for blood group AB?
AB (codominant)
what are the possible genotypes for blood group O?
OO
how many pairs of proteins are there in the Rh blood group system and how are they inherited?
3 pairs of proteins, inherited as triplet
what are the proteins of the Rh blood group?
- D or no D (d)
- C or c
- E or e
what type of antibodies are formed in the Rh blood group and how can they form?
immune only
form on exposure; transfusion, pregnacy and transplantation
how can the Rh phenotype be determined?
serologically
what antibodies will agglutinate CcDE?
agglutinate with anti-C, anti-c, anti-D, anti-E but not anti-e
what antibodies will aggluinate cdE?
anti-c
anti-E
there’s no anti-d
explain how a mother can damage the fetal RBCs?
Rh+ father and Rh- mother carrying her first Rh+ fetus
Rh antigens from the developing fetus can enter the mother’s blood during delivery
In response to the fetal Rh antigens, the mother will make anti-Rh antibodies
If the woman becomes pregnant again with another Rh+ fetus then her anti-Rh antibodies will cross the placenta and damage the fetal RBCs
what are the consequences of having a Rh- mother and her second Rh+ fetus?
Fetal anaemia – can be fatal
Neonatal jaundice – can cause brain damage
how is a Rh- mother with a Rh+ baby treated?
- 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 foetus from maternal sample now available to help targeted Anti D prophylaxis
name methods of good clinical blood transfusion practice?
Monitoring adverse reactions Patient identification Sample labelling Lab testing Selection of component Transfer to clinical area Appropriate use
how should RBCs be stored?
4 degC
shelf life of 35 days
name some indications for transfusions and give examples
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
(Anaemia due to Iron, B12 or folate deficiency) - Avoid transfusion– give haematinic replacement therapy instead.
what should you do after 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
how does an antibody screen work?
- indirect antigloblin test is used to detect IgG (alloantibodies formed after previous pregnancy or transfusion)
- Patient’s plasma mixed with group O cells expressing ALL the common blood group antigens – e.g. Rh C c D E e, and many others
- If an antibody is present it will bind to the antigen on the ‘detector’ red cells and screen will be positive
explain how an indirect antiglobulin test occurs?
Patient’s serum with IgG Incubation with reagent RBCs Binding of any IgG to reagent RBCs Incubation with antibodies to human Ig Agglutination (+ve indirect Coombs test)
how does serological cross match 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 carry out a blood transfusion?
Positively identify patient by name, DOB and hospital number Before transfusing must confirm Identity of patient Blood group of patient Blood group of the unit of blood Start transfusion Monitor closely (especially initially) Pulse, blood pressure and temperature
what are the signs and symptoms of a transfusion reaction?
Symptoms: restless, flushing, anxiety, abdominal pain, nausea and diarrhoea, abdominal pain, pain at venepuncture site
Signs: Fever, hypotension, haemoglobinguria
how do you treat someone who has had a possible transfusion reaction?
STOP TRANSFUSION
Maintain venous 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
when does a delayed haemolytic transfusion reaction occur and how does it present?
7 to 10 days post transfusion
Failure of haemoglobin to rise
Jaundice
what regulatory bodies do you report transfusion adverse effects to?
SHOT (Serious Hazards of Transfusion) - Collects information on adverse events and feedbacks to hospitals to improve transfusion overall safety
Blood Safety and Quality Regulations require mandatory reporting to:
MHRA (Medicines and Healthcare products Regulatory Agency)
SABRE (Serious Adverse Blood Reactions and Events)
