No difference in age of units transfused and pretransfusion Hb or HbS level. (A) There was no difference by analysis of variance in the age of the units transfused that were prestudy Rh negative, on-study Rh negative, or D-positive RHD genotyped on study (18 vs 16 vs 17 days). (B) There was no significant difference between average pretransfusion levels of Hb or (C) HbS level before and on study. Dots represent individual unit or laboratory values, and the dots connected by lines represent the average for each study subject in A-C.