A 60-year-old man on daratumumab for multiple myeloma requires pre-transfusion testing. His indirect antiglobulin test is repeatedly positive and pan-reactive, though he has no history of transfusion reactions. The most appropriate laboratory workaround is:
- A Treating reagent red cells with dithiothreitol to strip CD38 before antibody identification ✓
- B Washing the patient's red cells three times before testing
- C Performing elution studies on the patient's own red cells
- D Withholding transfusion until four weeks after the last daratumumab dose
Correct answer: A. Treating reagent red cells with dithiothreitol to strip CD38 before antibody identification
Explanation
Daratumumab binds CD38, which is weakly expressed on red cells. Circulating drug coats donor reagent cells during testing, producing a false-positive indirect antiglobulin test that masks clinically significant alloantibodies. Treating reagent red cells with dithiothreitol denatures CD38 without destroying other blood group antigens relevant to Indian panels, restoring valid antibody identification. Washing does not remove bound IgG, and waiting weeks is impractical in myeloma patients needing transfusion.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.