Drug-induced immune haemolytic anaemias

Question 1

What’s drug-induced immune haemolytic anaemia (DIIHA)

Answer 1

• patient produces an Aby towards a drug => immune-mediated RBC destruction
• may be intra- or extravasular heamolysis

Question 2

What’s the unifying theory

Answer 2

Aby can form against any one of the three epitopes
- Aby mainly to membrane & little bit of drug
- Aby to drug & membrane
- Aby to drug

Question 3

What’s the mechanism by which DIIHA causes DAT pos w/out Aby production

Answer 3

non-immunoligic protein adsorption (NIPA)
1. drug binds to & modifies RBC membrane
2. change in membrane => plasma components (igG, Alb, complement proteins) bind in non-immunologic (/non-specific) manner
= DAT pos w/out Aby production

Question 4

Describe the typical presentation of DIIHA

Answer 4

• HA after administered drug (need full drug Hx)
• present similar to warm AIHA

Question 5

Compare & contrast the presentation of warm AIHA and DIIHA

Answer 5

Both: pos auto control, pos DAT (most anti- IgG & -C3 pos)
DIIHA: Eluate is NEG(/weaker than DAT) bc removing Aby also removes drug from RBC membrane. Panagglutination disappears after stop giving drugs
WARM AIHA: eluate is pos. panagglutination continues even stop taking drugs

Question 6

Why do drug-induced antibodies cause panagglutination during initial testing?

Answer 6

bc have drug in plasma causing panagglutination

Question 7

What’s the difference b/w drug-dependent and drug-independent Aby

Answer 7

Dep: Drug present in patient’s plasma
Indep: doesn’t require presence of drug to bind to RBC = still binds even after drug is cleared (DAT pos)

Question 8

what’s the sub group in drug dependent Aby

Answer 8

• Aby reacting to drug-treated RBCs
• Aby reacting in the presence of drug: RBC reacted w/ serum AND drug in solution

Question 9

procedure for classifying drug-dependent Aby in DRUG-TREATED CELLS

Answer 9

• RBC incubated w/ drug for 1 hr @ RT = drug-treated RBC
• Treated RBC tested against (>) on IAT-saline method reading at 37C & AHG
  > patient plasma/serum: neat & 1/20 dilution
  > Eluate & last wash
  > Normal plasma/serum: Neat & 1/20 dilution
  > Pos control plasma/serum

Question 10

Why do we react the treated RBC to Neat & 1/20 dilution of patients’ plasma/serum

Answer 10

to see effect of non-immunoligic protein adsorption (NIPA), usually seen in Neat of Pt & Normal sample (pos rxn in IAT)
- nature of drug bound to RBC makes Aby stick to it (non-specifically i.e. no Aby made against it)

Question 11

procedure for classifying drug-dependent Aby in PRESENCE OF DRUG

Answer 11

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