Detection and quantification of IgG anti-PF4/H using CLIA and ELISA in patients with suspected and confirmed HIT. (A) Optical density (OD) results of both IgG anti-PF4/H assays according to HIT diagnosis (red dot) or no HIT diagnosis (blue dot). The red dashed line represents the positive threshold (OD > 1 U) for CLIA, and the black dashed line represents the positive threshold (OD > 0.5) for ELISA. There were discordant results between ELISA and/or CLIA for 5 patients with confirmed HIT (patients 1, 2, 3, 4, and 5). Characteristics of these discordant patients are described in Table 3. (B) AUC representing the performance of both tests in diagnosing HIT.