CLIA performance for diagnosis of HIT, including Bayesian analysis. (A) Results of the CLIA for the prospective study (n = 509 sera); analysis per manufacturer’s recommended cutoff (1.00 U/mL). HIT-positive vs HIT-negative status in relation to CLIA results, CLIA-pos (positive) vs CLIA-neg (negative). The corresponding 4Ts scores, shown as xx-xx-xx for each of the data groupings, correspond to low-intermediate-high (per real-time scoring by the investigators). (B) Post-test probabilities of HIT based upon combining pretest probability of HIT (per investigators’ 4Ts score) and CLIA test result at manufacturer’s recommended cutoff (Bayesian analysis). For each 4Ts classification (low, intermediate, and high), the probability of an SRA-positive (SRA-pos) test result is indicated. (C) Probability of HIT-positive vs HIT-negative result per strength of CLIA result (stratum-specific analysis). LR⁻ indicates likelihood ratio for HIT-negative status, whereas LR⁺ indicates likelihood ratio for HIT-positive status. As above, the corresponding 4Ts scores, shown as xx-xx-xx for each of the data groupings, correspond to low-intermediate-high (per real-time scoring by the investigators). (D) Post-test probabilities of HIT based upon combining pretest probability of HIT (per investigators’ 4Ts score) and stratum-specific CLIA test result (Bayesian analysis). The data shown are for the prospective study (n = 509 sera). (E) Distribution of CLIA test results for single-hospital consecutive patients with HIT. The figure shows the results using serum (n = 135). When plasma was used, the corresponding data distribution was similar, as follows: <0.40, n = 0; 0.40-0.99, n = 3; 1.00-4.99, n = 23; 5.00-19.99, n = 50; and ≥ 20.0, n = 59.