DTRs in patients with unexplained Rh antibodies. Percent hemoglobin S and hemoglobin levels in 3 representative cases of chronically transfused patients with anti-D, -C, and -e (see Table 2 for values of all DTRs associated with Rh antibodies). Each point represents a pretransfusion value coinciding with transfusions occurring at 3-week intervals. Arrows indicate time of antibody detection. The dotted line represents the mean percent hemoglobin S or hemoglobin level for that individual determined pretransfusion for 9 visits preceding antibody detection. The SD for means was calculated. The difference between the baseline and the value at time of antibody formation is expressed as a multiple of this SD, or Z-score. The gray shaded area indicates values that would have a Z-score <2. Z-score >2.0 for hemoglobin S level or <−2.0 for hemoglobin level correlates with P < .05. The double lines on the top charts indicate a several-month period when transfusions were discontinued.