DDAB development in patients 307 and 330.

Patient 307 (A) and patient 330 (B). The time course of DDAB development was monitored by the initial version of the DDAB ELISA (closed circles) and by FACS (open circles) versus decrease in platelet count (closed diamonds) during treatment with roxifiban. Antibody binding, denoted as delta, is measured by the difference between IgG bound to purified IIb/IIIa (ELISA) or platelets (FACS) in the presence of XP280 to that in the absence. Note that the increase in DDABs coincides with the decrease in platelet number. (C) Gel-purified platelets were incubated with 307 (left bars) or 330 (right bars) PPPs in the absence (no drug; open bars) or presence of XP280 (drug; filled bars). Dotted bars indicate that samples were incubated with XP280, but EDTA (9 mM) was added after the initial platelet-binding step. Platelets were removed by centrifugation and the resulting PPP tested in the DDAB ELISA. To prevent drug-dependent antibody binding of IgG to the no-drug wells, these wells were incubated with a GP IIb/IIIa antagonist that competes with XP280 for GP IIb/IIIa binding but fails to elicit binding of 307 or 330 DDABs. (D) The time courses of the DDAB titer rise and decline were analyzed in patients 307 (open circles) and 330 (closed circles) using the improved ELISA version. The PPP samples were diluted to be in the linear, dynamic range of the assay. The time of thrombocytopenia is indicated by an arrow.