The Blood Transfusion Lab Flashcards
Describe characteristics of antibodies
Antibodies are protein molecules –immunoglobulins (Ig)
Usually of the immunoglobulin classes: IgG and IgM
Found in the plasma
Produced by the immune system following exposure to a foreign antigen
Reactions to blood usually occurs when?
Reactions to blood usually occurs when the antibody in the plasma reacts with an antigen on the cells
Blood group systems - how many and which ones most important
There are 26 known blood group systems
ABO and Rh are clinically most important
Effect of antigens in transfused blood on pt
Antigens in transfused blood can stimulate a patient to produce an antibody but only if the patient lacks the antigen themselves
Relation of antibody prod with transfusions
The frequency of antibody production is very low but increases the more transfusions that are given
Describe ways to stim antibody prod
Blood transfusion
i.e. blood carrying antigens foreign to the patient
Pregnancy
Fetal antigen entering maternal circulation during pregnancy or at birth
Environmental factors
(i.e. naturally acquired e.g. anti-A and anti-B)
Effect of antigen-antibody reactions in vivo
in vivo (in the body) leads to the destruction of the cell either:
directly when the cell breaks up in the blood stream (intravascular)
indirectly when liver and spleen remove antibody coated cells (extravascular)
Agglutination - define
Agglutination is the clumping together of red cells into visible agglutinates by antigen-antibody reactions
Agglutination - cause
Agglutination results from antibody cross-linking with the antigens
List what agglutination can identify and what allows it to do this
As the antigen-antibody reaction is specific, agglutination can identify:-
The presence of a red cell antigen
i.e. blood grouping
The presence of an antibody in the plasma
i.e. antibody screening/identification
ABO antibodies effect
ABO antibodies can activate complement causing INTRAVASCULAR HAEMOLYSIS
Group A -
RBC type
AB present
AT present
Group A -
RBC type = A
AB present = anti-B
AT present = A antigen
Group B -
RBC type
AB present
AT present
Group B -
RBC type = B
AB present = anti-A
AT present = B antigen
Group AB -
RBC type
AB present
AT present
Group AB -
RBC type = AB
AB present = none
AT present = A and B antigens
Group O -
RBC type
AB present
AT present
Group O -
RBC type = O
AB present = anti-A and anti-B
AT present = no antigens
Result for testing patient’s red cells with anti-A, anti-B and anti-D
agglutination shows that a particular antigen is on the red cells
no agglutination shows the antigen is absent
Result for testing patient’s plasma with A cells and B cells
agglutination shows that a particular antibody is in the plasma or serum
no agglutination shows the antibody is absent
ABO Compatibility - recipient blood group O
Only compatible with donor red cell O
ABO Compatibility - recipient blood group A
Only compatible with donor red cells O and A
ABO Compatibility - recipient blood group B
Only compatible with donor red cells O and B
ABO Compatibility - recipient blood group AB
Compatible with donor red cells O, A, B + AB
Rh grouping system - characteristics
50+ antigens:
Most important antigen is called D.
People with D antigen are D positive (85% of UK)
People who do not produce any D antigen are D negative (15%)
The other 4 main antigens are known as C, c, E and e
Rh (D) typing - conditions and result
Must be tested in duplicate (or tested each time and compared to historical result)
Patient / Donor classified as D pos or D neg
Clinical significance of Rh in transfusion
Transfusion
D antigen is very immunogenic and anti-D is easily stimulated - PREVENTION!
All Rh antibodies are capable of causing severe transfusion reaction- ANTIBODY DETECTION
Clinical significance of Rh in pregnancy
Pregnancy
Rh antibodies are usually IgG and can cause haemolytic disease of the newborn
Anti-D is still most common cause of severe HDN
Development of Haemolytic disease of the Newborn (HDN)
Rh+ father
Rh- mother carrying first Rh+ fetus
- Rh antigens from developing fetus can
enter the mother’s blood during
delivery
Mother responds w/anti-Rh antibodies
If another Rh+ fetus, her anti-Rh antibodies will cross placenta + damage fetal RBC
HDN – laboratory testing and result
Blood group and antibody screen at antenatal booking to identify pregnancies at risk of HDN
D negative women who may need anti-D prophylaxis
Describe quantification of atypical antibodies
Atypical antibodies are quantified periodically to assess their potential effect on the fetus
RAADP function
An injection of anti-D will bind to and remove any fetal D positive red cells in the circulation
RAADP doses
1500 iu of anti-D is given routinely at 28 weeks and a smaller dose (usually 500 iu) after delivery if baby RhD+
In some hospitals 2 smaller (500 iu) doses are given at 28 and 34 weeks instead of the 1 larger dose
List when Anti-D is also given
Anti-D is also given after any event that may cause a feto-maternal haemorrhage (bleed between mum and fetus) such as:
Abdominal trauma
Intrauterine death
Spontaneous or therapeutic abortion
Importance of screening antibodies that can cause haemolytic transfusion reaction
It is important that we screen for these antibodies
so that If detected, antigen negative blood can be provided to avoid causing a immune reaction.
Antibody screening - process
Patients serum is mixed with 3 selected screening cells, incubated for 15 minutes at 37oc and then centrifuged for 5 minutes.
Any clinically significant antibodies reacting at body temp should be detected and then identified using panel of known phenotyped red cells.
Specific antigen negative blood can then be provided for these patients to avoid stimulating an immune response.
If an antibody is detected we must:-
If an antibody is detected we must:-
Identify the antibody
Assess its clinical significance
- For transfusion
- In pregnancy
How to Identify an antibody
Compare pattern of reactions with each reagent cell of ID panel with the pattern of antigens on the reagent cells
Matching pattern will identify the antibody
Describe how IgG spanning the gap between RBCs is made possible
IgM antibodies can span the gap between RBCs
IgG can not, because too small to overcome ZETA potential (+ve charge)
LISS (low ionic strength saline) is negatively charged, so neutralises positive ZETA potential.
Therefore IgG can now span the gap.
Explain formation of zeta potential
RBC surface = -vely charged due to the ionization of the carboxyl group of sialic acid
In saline RBC attract +vely charged Na+, and an ionic cloud will form around each cell
Thus the cells will be repelled and stay a certain distance apart.
ZP = measure of the difference in charge at the surface of the membrane and the outer edge of the ionic cloud (slipping plane).
Indirect anti-globulin test (IAT) - describe action
LISS counteracts Zeta potential.
Results in agglutination
Indirect anti-globulin test (IAT) - describe uses
Used for:
Used to detect IgG antibodies
Screening for antibodies
Identifying antibodies
Cross-matching donor blood with recipient plasma when there are known antibodies or a previous history of antibodies.
Immediate spin cross-match (ISX) - describe process
Checking donor red cells against patients plasma
ABO check
Incubate for 2 – 5 minutes (room temp), spin and read.
Immediate spin cross-match (ISX) - purpose
used to detect ABO incompatibility between donor red cells (RBCs) and the serum of the intended recipient.
Immediate spin cross-match (ISX) - result
May be positive in the absence of ABO incompatibility (false positive)
or it may be negative when ABO incompatibility exists (false negative).
Immediate spin cross-match (ISX) - used when
Antibody screen is negative
Full Indirect Antiglobulin test (IAT) cross-match - used when
Antibody screen positive or patient has known antibody history.
Full Indirect Antiglobulin test (IAT) cross-match - process
Select antigen negative donor red cells and incubate with patient serum for 15 minutes at 37oC
RBC transfusion in what form
Concentrated red cells (packed cells) in a suspension of SAGM
What must be done after significant bleeding
If significant bleeding anticipated, activate the major haemorrhage protocol
Fresh Frozen Plasma - composition
FFP contains all clotting factors
Fresh Frozen Plasma - use
Given for coagulopathy with associated bleeding
Fresh Frozen Plasma - requires what
Requires clotting screens to monitor
Fresh Frozen Plasma - life length
Only has 24 hour life after thawing
five days for major haemorrhage
Platelet transfusion in what form
Adult pool of platelets from 4 donors (suspended in plasma from 1 donor)
Platelet transfusion - use
Platelets required to create clots to reduce bleeding
Platelet transfusion - why pt history important
Some drugs given to reduce efficacy of platelets (antiplatelet agents) so patient history important
Cryoprecipitate - composition
Contains Factor VIII, VWF and fibrinogen
Cryoprecipitate - how many units used
2 units usually given at one time
Cryoprecipitate - describe monitoring
Monitor fibrinogen levels by clotting screens
List the aspects of regulation of Blood
EU Blood Safety Directive Blood Safety Quality Regulations Better Blood Transfusion 3 MHRA inspections CPA inspections
Serious Hazards of Transfusion (SHOT) - describe action required
Serious Hazards of Transfusion (SHOT):
Voluntary reporting
Report all Serious adverse Events (SAE) and Serious adverse reactions (SAR)
Serious Adverse Blood reactions and events (SABRE) - describe action required
Serious Adverse Blood reactions and events (SABRE):
Mandatory reporting
Report all SAR and SAE where the root cause error was the Quality system
