Determining a safe pre-transfusion protocol for multiple myeloma patients on anti-CD38 treatment

Daratumumab is a monoclonal antibody therapy used to treat multiple myeloma. It has introduced challenges for blood transfusion laboratories to provide safe red cells for transfusion due to the cross-reactivity of daratumumab with red cell surface antigens on antibody screening cells, resulting in panreactivity and preventing the exclusion of alloantibodies. NHS Lothian transfusion protocol for patients on daratumumab involves pre-daratumumab extended patient phenotyping of significant RBC antigens and transfusion of RhD (CcEe) and K phenotype matched Red Cell Concentrate (RCC) without performing any pre-transfusion antibody screening.

To determine alloimmunisation rates following the current protocol the laboratory information management system (LIMS) was interrogated to determine if patients previously on daratumumab had developed antibodies in response to transfused RCCs. Grifols sCD38 was used to neutralise daratumumab in transfused patients. sCD38 was used to (1) assess alloimmunisation rates in patients on treatment (2) assess how it could be applied in a routine pre transfusion testing protocol.

Since 2018, 185 patients started daratumumab therapy in Lothian. There was a record of RCC transfusion in 102 patients. From the LIMS, negative antibody screens were recorded in 21 patients post-daratumumab treatment. No alloimmunisation was detected from 34 transfused patients still on daratumumab.

Low alloimmunisation suggests NHS Lothian protocol for transfusion of daratumumab patients is safe. Extended phenotyping of patients pre-treatment may be extensive and unnecessary due to the low alloimmunisation rate. Implementation of sCD38 reagent into pre-transfusion testing can reduce extensive pre-treatment testing and improve the safety of transfusion by exclusion of alloantibodies in daratumumab patients.