TSP1 release in the PF4-TRA and heparin-TRA were well correlated, and cryopreserved platelets support FcᵞRIIa-mediated platelet activation. (A) Ten HIT-suspected patient samples with sufficient volumes to test in both the PF4-TRA and heparin-TRA stimulated similar levels of TSP1 release in both the PF4-TRA and heparin-TRA (R2 = 0.724; P = .0018). Data are from technical duplicates, and correlation was determined by linear regression analysis (black solid line) with 95% CI (dashed lines) displayed. (B) TSP1 release induced by HIT and VITT samples from cryopreserved platelets incubated with monoclonal antibody IV.3 or IC in the PF4-TRA are shown. Data are from technical duplicates with mean ± SD displayed. ∗∗P < .005; ∗∗∗P < .001. IC, isotype control; ns, not significant.
