Anti-PF4 autoantibodies were detected in all samples by ELISA but not CLIA. (A) ELISA reactivity was inhibited to optical density <0.3 by heparin in all samples (2 U/mL, data not shown). (B) Binding of antibodies from patient sera to healthy donor platelets in the presence of AZD1222 was suppressed by heparin. Fluorescent intensity ratio of AZD1222 (or AZD1222 + heparin 100 U/mL) to buffer is shown. (C) Schistocytes in blood smear high power field in patient 1, indicative of TMA, on day 4. (D) Course of selected laboratory markers over time. X-axes show days of hospital stay. Y-axes on the left are for all panels.