Anti-CD47 Interference

Background:

Anti-CD47 (Hu5F9-G4)interferes with all phases of pretransfusion testing, including ABO reverse typing.

Anti-CD47 (Hu5F9-G4) is a human monoclonal IgG4 antibody used to treat hematologic or solid malignancies.  CD47 is a glycoprotein expressed on all cells. 

All plasma samples reacted 3-4+ in all phases with RBCs, including immediate spin.  Stronger reactivity may occur in D-negative RBCs.  Plasma reacted with DTT, trypsin, papain, alpha-chymotrypsin or WARM (warm autoantibody removal medium—Immucor). 

DAT and autocontrol are negative or weak whereas eluates are 3+ reactive.  Reactivity is removed by multiple alloadsorptions with papain-treated cells or pooled platelets.  PEG absorption is invalid due to precipitation of the antibody.  Gamma heavy-chain specific AHG reagent (Gamma-clone IgG—Immucor) does not detect IgG4 antibodies.

Process:

  1. Always check medication history for anti-CD47 treatment.
  2. If positive, use gamma heavy-chain specific AHG reagent (Gamma-clone IgG) for IAT.

The following table summarizes anti-CD47 reactivity and compares it to anti-CD38—see reference below.

Reference:

Randall Velliquette et al, Anti-CD47 Interference in Red Cell and Platelet Testing, Transfusion 2019; 59, 730-737