Practical 3: RhD anomalies Flashcards
What should you first do if an anomaly comes up?
Repeat the test going back to tubes i.e. repeat everything including making up your rbc suspension
What should you do if there is a repeatable anomalous result
Report it to a senior person in the lab
Request a repeat fresh sample
List the different types of common problems
(2)
Groups differ from that of previous group of the patient
Forward group does not correspond with reverse group
What is a discrepancy?
When the red cell testing does not match the serum testing
What three discrepancies might occur when the forward group does not correspond with the reverse
Weak reaction
Missing reactions
Extra reactions
Why might there by a weak/missing reaction?
(5)
Paediatric
Elderly patient
Hypogammaglobulinaemia
Post bone marrow transplant
SCID
Why might there by extra reactions?
(7)
Possible A2 with anti-A1 antibody
Blood transfusion
Cold agglutinins
Post bone marrow transplant
Polyagglutination
Acquired B antigen
Roulouex - rbcs stack on top of each other not agglutinated -> caused by patients plasma -> wash rbcs
What should you do if you think a patient is group A2?
(2)
Subtype the patient with anti-A1
Rule out cold agglutinins by warming the sample
What should you do if you have a group O patient with no reverse groups i.e. no antibodies
(3)
Check patient history
Are they a baby
Do they have hypogammaglobulinaemia or SCID
What should you do if you suspect an acquired B antigen
(3)
This is very rare so it’s more than likely cold agglutinins
But if this isn’t resolved by rerunning the test or warming the sample then report to senior staff
Double check patient’s history e.g. do they have a gastric carcinoma which would cause acquired B
What result would indicate weak partial D
If only one of the anti-D anti-sera worked
What should you do if you suspect weak partial anti-D
(2)
Need to rule out anti-C or E by using a BioVue/Diamed CDE gel
Incubate at 37 degrees for 15 mins and retest to see if other anti-D becomes positive or if result improves
What two gels can we use to phenotype CDE?
BioVue CDE gel
Diamed CDE gel
What should you do if RhD control comes up positive
Run a Direct Coombs test
- is the agglutination caused by other non ABO blood groups
Is there cold aglutinins or rouloux
List the five causes of extra antigens
Group A with acquired B antigen
B(A) phenotype
Polyagglutination
Rouleaux
Hematopoietic progenitor cell transplants
List the five causes of extra antibodies
A subgroups with anti-A1
Cold alloantibodies
Cold autoantibodies
Rouleaux
IVIG (intravenous Ig transfusion)
List the three causes of missing or weak antigens
ABO subgroup
Pathologic etiology
Transplantation
List the four causes of missing or weak antibodies
Newborn
Elderly
Pathologic etiology
Immunosuppressive therapy for transplantation
What are the two reasons for mixed-field reactions
Transfusion of group O to group A, B, or AB
Haematopoietic progenitor stem cell transplants
What causes rouleaux and how do you solve it
(3)
Caused by increased plasma protein
Solved via saline displacement in reverse group
Solved by washing patient rbcs in forward group
Why would an A2 subgroup have a weaker reaction
Subgroup has less antigen sites on the surface of the rbc
Therefore will show weak or missing reaction
How do you solve a A2 subgroup
Test with Anti-A1 (Dolichos Biflorus)
What causes acquired-B-phenotype
Lower GI tract disease
Cancer of colon/rectum
Intestinal obstruction
Gram negative septicemia caused by E.Coli
How do you resolve acquired B
(2)
Test patients serum with their own rbcs -> patients own anti-B will not react with the acquired B antigen on their red cell
Or use an anti-B reagent produced by some manufacturers which also shouldn’t react
How does acquired B come about
Bacterial (E.Coli) have a deacetylating enzyme that affects the A sugar
It removed the acetyl group from A antigen to form B antigen
