A 68-year-old man with relapsed multiple myeloma starts daratumumab. Before his second cycle, the transfusion laboratory calls to report difficulty completing antibody screening and crossmatching. The correct explanation and action are:
- A Daratumumab coats red cells via CD38, interfering with indirect antiglobulin testing; the drug should be documented so special techniques can release masked antibodies ✓
- B The drug causes cold agglutinin disease; all transfusions should be avoided until treatment ends
- C He has developed true alloantibodies from prior transfusion; the drug should be stopped permanently
- D Daratumumab causes haemolysis by complement fixation; washed red cells must be used exclusively
Correct answer: A. Daratumumab coats red cells via CD38, interfering with indirect antiglobulin testing; the drug should be documented so special techniques can release masked antibodies
Explanation
CD38 is weakly expressed on red blood cells, so circulating daratumumab binds recipient erythrocytes and produces panreactivity on the indirect antiglobulin test, mimicking multiple alloantibodies. No haemolysis occurs. The solution is administrative: inform the blood bank, record recent dosing, and use dithiothreitol-treated cells or other adsorption techniques to uncover genuine clinically significant antibodies. Stopping the drug is unnecessary, and cold agglutinins involve IgM against I antigen, unrelated to CD38 therapy.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.