Practical 3: RhD anomalies

Question 1

What should you first do if an anomaly comes up?

Answer 1

Repeat the test going back to tubes i.e. repeat everything including making up your rbc suspension

Question 2

What should you do if there is a repeatable anomalous result

Answer 2

Report it to a senior person in the lab

Request a repeat fresh sample

Question 3

List the different types of common problems
(2)

Answer 3

Groups differ from that of previous group of the patient

Forward group does not correspond with reverse group

Question 4

What is a discrepancy?

Answer 4

When the red cell testing does not match the serum testing

Question 5

What three discrepancies might occur when the forward group does not correspond with the reverse

Answer 5

Weak reaction

Missing reactions

Extra reactions

Question 6

Why might there by a weak/missing reaction?
(5)

Answer 6

Paediatric

Elderly patient

Hypogammaglobulinaemia

Post bone marrow transplant

SCID

Question 7

Why might there by extra reactions?
(7)

Answer 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

Question 8

What should you do if you think a patient is group A2?
(2)

Answer 8

Subtype the patient with anti-A1

Rule out cold agglutinins by warming the sample

Question 9

What should you do if you have a group O patient with no reverse groups i.e. no antibodies
(3)

Answer 9

Check patient history

Are they a baby

Do they have hypogammaglobulinaemia or SCID

Question 10

What should you do if you suspect an acquired B antigen
(3)

Answer 10

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

Question 11

What result would indicate weak partial D

Answer 11

If only one of the anti-D anti-sera worked

Question 12

What should you do if you suspect weak partial anti-D
(2)

Answer 12

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

Question 13

What two gels can we use to phenotype CDE?

Answer 13

BioVue CDE gel

Diamed CDE gel

Question 14

What should you do if RhD control comes up positive

Answer 14

Run a Direct Coombs test

• is the agglutination caused by other non ABO blood groups

Is there cold aglutinins or rouloux

Question 15

List the five causes of extra antigens

Answer 15

Group A with acquired B antigen

B(A) phenotype

Polyagglutination

Rouleaux

Hematopoietic progenitor cell transplants

Question 16

List the five causes of extra antibodies

Answer 16

A subgroups with anti-A1

Cold alloantibodies

Cold autoantibodies

Rouleaux

IVIG (intravenous Ig transfusion)

Question 17

List the three causes of missing or weak antigens

Answer 17

ABO subgroup

Pathologic etiology

Transplantation

Question 18

List the four causes of missing or weak antibodies

Answer 18

Newborn

Elderly

Pathologic etiology

Immunosuppressive therapy for transplantation

Question 19

What are the two reasons for mixed-field reactions

Answer 19

Transfusion of group O to group A, B, or AB

Haematopoietic progenitor stem cell transplants

Question 20

What causes rouleaux and how do you solve it
(3)

Answer 20

Caused by increased plasma protein

Solved via saline displacement in reverse group

Solved by washing patient rbcs in forward group

Question 21

Why would an A2 subgroup have a weaker reaction

Answer 21

Subgroup has less antigen sites on the surface of the rbc

Therefore will show weak or missing reaction

Question 22

How do you solve a A2 subgroup

Answer 22

Test with Anti-A1 (Dolichos Biflorus)

Question 23

What causes acquired-B-phenotype

Answer 23

Lower GI tract disease

Cancer of colon/rectum

Intestinal obstruction

Gram negative septicemia caused by E.Coli

Question 24

How do you resolve acquired B
(2)

Answer 24

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

Question 25

How does acquired B come about

Answer 25

Bacterial (E.Coli) have a deacetylating enzyme that affects the A sugar

It removed the acetyl group from A antigen to form B antigen