Practical 3: RhD anomalies Flashcards

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1
Q

What should you first do if an anomaly comes up?

A

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

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2
Q

What should you do if there is a repeatable anomalous result

A

Report it to a senior person in the lab

Request a repeat fresh sample

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3
Q

List the different types of common problems
(2)

A

Groups differ from that of previous group of the patient

Forward group does not correspond with reverse group

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4
Q

What is a discrepancy?

A

When the red cell testing does not match the serum testing

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5
Q

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

A

Weak reaction

Missing reactions

Extra reactions

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6
Q

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

A

Paediatric

Elderly patient

Hypogammaglobulinaemia

Post bone marrow transplant

SCID

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7
Q

Why might there by extra reactions?
(7)

A

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

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8
Q

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

A

Subtype the patient with anti-A1

Rule out cold agglutinins by warming the sample

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9
Q

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

A

Check patient history

Are they a baby

Do they have hypogammaglobulinaemia or SCID

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10
Q

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

A

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

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11
Q

What result would indicate weak partial D

A

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

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12
Q

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

A

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

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13
Q

What two gels can we use to phenotype CDE?

A

BioVue CDE gel

Diamed CDE gel

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14
Q

What should you do if RhD control comes up positive

A

Run a Direct Coombs test

  • is the agglutination caused by other non ABO blood groups

Is there cold aglutinins or rouloux

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15
Q

List the five causes of extra antigens

A

Group A with acquired B antigen

B(A) phenotype

Polyagglutination

Rouleaux

Hematopoietic progenitor cell transplants

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16
Q

List the five causes of extra antibodies

A

A subgroups with anti-A1

Cold alloantibodies

Cold autoantibodies

Rouleaux

IVIG (intravenous Ig transfusion)

17
Q

List the three causes of missing or weak antigens

A

ABO subgroup

Pathologic etiology

Transplantation

18
Q

List the four causes of missing or weak antibodies

A

Newborn

Elderly

Pathologic etiology

Immunosuppressive therapy for transplantation

19
Q

What are the two reasons for mixed-field reactions

A

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

Haematopoietic progenitor stem cell transplants

20
Q

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

A

Caused by increased plasma protein

Solved via saline displacement in reverse group

Solved by washing patient rbcs in forward group

21
Q

Why would an A2 subgroup have a weaker reaction

A

Subgroup has less antigen sites on the surface of the rbc

Therefore will show weak or missing reaction

22
Q

How do you solve a A2 subgroup

A

Test with Anti-A1 (Dolichos Biflorus)

23
Q

What causes acquired-B-phenotype

A

Lower GI tract disease

Cancer of colon/rectum

Intestinal obstruction

Gram negative septicemia caused by E.Coli

24
Q

How do you resolve acquired B
(2)

A

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

25
Q

How does acquired B come about

A

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

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