Samples were referred to us (the reference laboratory) and were found to contain a pan reactive antibody detected by all IAT techniques available to us (including two gel technologies, and tube techniques perfomed with a range of different media). The 'Auto' and DAT were negative. An elution of the patient's red cells was also 'negative'. The patient had been transfused a single red cell unit, about 6 weeks prior to referral (no previous transfusion history), when their IAT red cell antibody screen was negative. Reactivity with test cells was now a, relatively, uniform positive grade 3 (on a scale of 1-5), but some stronger and weaker reactions were noted. Reaction strength increased when an enzyme IAT was performed, using papain treated red cells. We initially investigated for the possible presence of an antibody to a higher frequency antigen, but found no negative results with, for example, Csa-, Lan-, Vel-, Lub-, Kpb-, CR1-, Yta-, k-, red cells. The plasma hade a titre of 2048 against each of the red cells of a 3 cell antibody screening 'set'. We were then informed that the patient had started treatment with anti-CD38, immediately after their transfuson, 6 weeks ago. We treated a standard red cell antibody identification panel with DTT, and found that this failed to react with the sample. This result, in combination with results from an extended phenotype, allowed us to rule out most significant antibodies (other than those with antigens that are sensitive to DTT treatment and that the patient lacked) and be fairly confident taht the antibody we were detecting was the anti-CD38. What I want to know is why are the patient's 'Auto' and DAT negative, where has their CD38 antigen gone? Also, has anyone who has encountered this antibody come up with any other methods for 'dealing' with it?