Antibody and CD38 antigen levels are decreased on RBCs isolated from DARA treated individuals. (A) Hemoglobin (Hgb) levels of DARA-treated patients before DARA exposure and at weeks 1, 2, 3, and 4 of treatment (week 4 n = 11, as hemoglobin data were not available for 2 patients). (B-E) Flow cytometric detection of in vivo DARA binding (B), CD38 antigen (C), Kell antigen (D), and Duffy antigen (E) on RBCs isolated from DARA-treated and nontreated patients. Significance was determined by Student t test (****P ≤ .0001). MFI, mean fluorescence intensity.