Daratumumab (DARA, Anti-CD38) and Interference with Blood Compatibility Testing

 

Patient selection: interference with blood compatibility testing, with a positive direct antiglobulin test (DAT)

 

Identification of the patient as having multiple myeloma and of being treated with daratumumab can greatly simplify the workup. Otherwise the patient needs to be evaluated for all causes of a positive DAT.

 

One way of resolving the problem is to treat the reagent red blood cells with dithiothreitol (DTT), which destroys CD38. This will eliminate the interference from daratumumab.

 

Unfortunately DTT also destroys Kell antigen on the reagent red cells, which means that anti-Kell antibodies may be missed. The workaround for this is to make sure that the units that the patient receives are Kell antigen negative (although this may not be necessary if the patient is known from the past to be K-positive).