Based on this evaluation, 5 of 10 PEA+/SRApatients were deemed likely to have HIT (Table 5; supplemental Figure 2). may provide an option for rapid and conclusive results. Based upon predefined criteria that combined 4Ts scores and HIT ELISA results, 409 consecutive adults suspected of having HIT were classified as disease positive, negative, or indeterminate. Patients deemed HIT indeterminate were considered disease negative in the primary analysis and disease positive in a sensitivity analysis. The ability of PEA and SRA to identify patients judged to have HIT was compared using receiver operating characteristic curve statistics. Using these predefined criteria, the diagnostic accuracy of PEA was high (area under the curve [AUC], 0.94; 95% confidence interval [CI], 0.87-1.0) and related to that of SRA (AUC, 0.91; 95% CI, 0.82-1.0). In level of sensitivity analysis, the AUCs of PEA and SRA were also related at 0.88 (95% CI, 0.78-0.98) and 0.86 (95% CI, 0.77-0.96), respectively. The PEA, a theoretically simple nonradioactive assay that uses 20-fold fewer platelets compared with the SRA, experienced high accuracy for diagnosing HIT. Widespread use of the PEA may facilitate timely and more effective management of individuals with suspected HIT. == Visual Abstract == == Intro == Heparin-induced thrombocytopenia (HIT) is definitely a life-threatening complication of heparin therapy caused by antibodies that identify the platelet-specific CXC chemokine, platelet element 4 (PF4), when it binds to heparin or additional negatively charged macromolecules.1-5Despite improvements in the understanding of HIT pathogenesis since it was recognized as a medical entity several decades ago, patients suspected of having PQM130 this problem continue to experience significant morbidity, particularly thrombosis, bleeding, and amputation, and 10% of cases end fatally.6Once HIT is suspected, immediate discontinuation of heparin and institution of an alternate anticoagulant are necessary. A false-positive test for HIT or a delay in excluding HIT needlessly subjects a patient to the substantial risks associated with treatment having a heparin option. Conversely, a false-negative HIT test can lead to catastrophic thrombosis or death. Pretest probability of HIT can be identified utilizing clinical scores such as the 4Ts score.7Helpful information can also be gained by performing a relatively simple laboratory Slc2a3 test, the PF4/polyanion enzyme-linked immunosorbent assay (ELISA), which detects antibodies found in virtually all patients with HIT.8Because of its poor diagnostic specificity, however, the greatest value of the PF4 ELISA lies in the ability of a negative result to exclude the analysis. In contrast, many individuals having a positive ELISA result do not, in fact, have HIT. The serotonin launch assay (SRA) detects pathogenic HIT antibodies preferentially and is widely considered to be the gold-standard laboratory test for HIT analysis.2Thrombocytopenia and thrombosis in HIT result from the actions of a subset of heparin-induced pathogenic antibodies that activate platelets. Regrettably, however, the SRA is definitely theoretically demanding and is regularly available only through a few research laboratories, precluding its impact on early decisions for individuals with suspected PQM130 HIT. An alternative platelet-activation assay, the PF4-dependent P-selectin manifestation assay (PEA), is based on the finding that incubation of platelets with PF4 primes them for acknowledgement by pathogenic heparin-induced antibodies, which, upon binding to PF4-primed PQM130 platelets, induce FcRIIa (CD32)dependent platelet activation and P-selectin (CD62p) surface manifestation.9The PEA is technically simple, uses fewer platelets, and, unlike the SRA, requires no radioactive reagents, with the potential to make same-day results available to help with patient care decisions. Limited clinical studies possess suggested the accuracy of PF4-enhanced platelet activation assays for recognition of individuals who have HIT is comparable to or better than that of the SRA,10,11whereas others have shown that use PQM130 of PF4-treated platelets in practical platelet screening can detect pathogenic HIT antibodies earlier in the disease program.12,13Here, we describe results of a multicenter, prospective, blinded study designed to compare the PEA and SRA inside a large-scale clinical setting. ==.