Impact of anticoagulants on VITT–IgG-mediated platelet adhesion/thrombus formation. (A) Platelets from healthy individuals were incubated with IgGs from healthy controls (HCs) or VITT patients before calcein staining and reconstitution with autologous whole blood and perfusion through BioFlux microfluidic channels. IgG concentrations were measured using nanodrop (mean IgG concentration, 15.10 ± 2.14 mg/mL). Where indicated, samples were treated with different concentrations of anticoagulants: low-dose heparin (0.1 U/mL), therapeutic-dose heparin (0.5 U/mL), TD danaparoid (0.8 U/mL), TD and HD fondaparinux (1 and 8 µg/mL), and TD and HD of argatroban (0.8 and 8 µg/mL). (B) IVIG was added alone or in combination with anticoagulants. Each dot represents 1 VITT patient IgG. Images were acquired at 20× magnification using an inverted Olympus IX73 or Zeiss Axio Observer 7 fluorescence microscope. Thrombus formation was determined as the %SAC by adherent platelets using ImageJ. Images were processed identically using automated or manually adjusted threshold settings and exclusion of image artifacts. Violin plots showing the distribution of the values were generated using Graphpad Prism 8. This figure represents values from the same experimental setup. The figure is split into 2 different panels (1A and 1B) for easier interpretation of the results. Therefore values and representative images in the HCs group and some in untreated VITT IgGs are presented in both panels. HD, high dose; LD, low dose; ns, not significant; TD, therapeutic dose. *P < .05, **P < .01, and ***P < .001.