Daratumumab (i.e. DARZALEX™ or DARA), from Janssen Biotech (Johnson & Johnson), is a new drug recently approved by the FDA to treat patients with refractory multiple myeloma. This monoclonal antibody is directed against CD38, which is strongly expressed on malignant plasma cells, but also weakly present on red blood cells (RBCs). Therefore, DARA can bind to RBCs and interfere with antibody screening, antibody identification and compatibility testing. Patients may be on this treatment for 6 months or more, and the RBC binding effects of the drug may persist for up to 6 months after drug discontinuation. It is important that the transfusion service is notified whenever a patient is scheduled to begin or has begun DARA treatment.
When sending patient samples to the IRL, be sure to indicate on the IRL order form if the patient is on DARA or is scheduled to being DARA treatment. Contact your local blood center or Vitalant for more information and for recommendations to mitigate the serologic interference, which could delay appropriate patient care and transfusions.