Effect of anticoagulants on VITT IgG binding to microtiter plate-bound PF4. Binding of (A) total VITT IgG and (B) anti-PF4 specific VITT IgG to PF4 (10 μg/mL) in the absence or presence of argatroban, bivalirudin, danaparoid, fondaparinux, or UF heparin. The data are representative of 3 patient samples with VITT. Binding of total HIT IgG to PF4 (10 μg/mL) and heparin (0.1 U/mL) in the absence or presence of (C) argatroban, bivalirudin, danaparoid, fondaparinux, or (D) UF heparin. IgG binding to PF4 calculated relative to VITT IgG alone (A, B), HIT IgG with 0.1 U/mL heparin (C), or HIT IgG alone (D). Dashed lines indicate the therapeutic plasma range.