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Irregular erythrocyte antibody screening tests in patients treated with CD38 monoclonal antibodies lead to falsepositive results because of the surface expression of CD38 on red-blood-cell reagents. We obtained false-positive results for blood samples from multiple patients using the automated pre-transfusion testing system IH-1000 (BIO-RAD) after testing a blood sample taken from a patient treated with daratumumab. This may have been caused by residual daratumumab-bound erythrocytes from the treated patient in the device. Such an occurrence may be more or less likely depending on conditions such as drug concentration and measurement sequence. Further verification is needed. Thus, caution is warranted when testing blood samples from patients on anti-CD38 antibody therapy using an automated pre-transfusion testing system.

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