Antibodies (historical or newly developed) reported in n = 1742 pSCDs who received transfusion. (A) Distribution of antibodies per antibody specificity and (B) distribution of antibodies per patient; there were 498 different combinations of antibodies. Antibodies or combinations reported in <5 patients are not shown. Antibodies to HFAs included anti-Fy3 (n = 58), anti-Fy5 (n = 17), anti-Js^b (n = 5), anti-U (n = 9), anti-Co^a (n = 3), (n = 1), and anti-Hy, anti-Jo^a, and anti-En^a (n = 1 each). n = 31 antibodies to HFAs were not identified at the first occurrence. HTLA, high titer-low affinity; NI-LFA, nonidentified low-frequency antigen; US, unspecified specificity (which could be a previously identified antibody that was not characterized to save resources or for lack of appropriate panel cells, or an emerging antibody).