Kaplan-Meier curve for the number of RBC units received before the first positive antibody screen in n = 643 patients for whom no antibodies had been reported before the study period or before their first transfusion. The first positive antibody screen for each patient is counted as an event. Curves are shown for all antibodies and for subgroups: WAAs, AUS, antibodies to RH antigens (D, C, E, c, and e) or Kell (RH-K), to AEP, and to HFA. (A) The full cohort. (B) Zoom-in focusing on 0 to 50 RBCus, with a vertical bar representing 20 RBCus, after which 90% of patients who will make antibodies to HFA have made their first such antibody, and >75% of patients who will make antibodies to RH-K antigens, AEPs, WAAs, and AUSs will have made their first such antibody. The figure was generated with software SAS 9.4 and R.