A clinical-laboratory approach contributing to a rapid and reliable diagnosis of heparin-induced thrombocytopenia

Introduction: Heparin-induced thrombocytopenia (HIT) remains a very challenging diagnosis. The first objective of this study was to compare the performance of the IDH/PF4 PaGIA (R) with the Asserachrom (R) HPIA ELISA. The main purpose was to evaluate the diagnostic utility of the combination of the H/PF4PaGIA (R) with the clinical "4T's" score as a screening strategy. Materials and Methods: 102 patients with clinical suspicion of HIT were classified into risk groups using the 4T's score. The presence of HIT antibodies was assessed by two immunoassays and confirmed by a functional flow cytometric assay. Results: Comparison of the ID-H/PF4 PaGIA (R) with the Asserachrom (R) HPIA ELISA demonstrated a comparable technical performance, being an excellent screening test to rule out HIT (negative predictive value or NPV=100%). According to the 4T's score, HIT was excluded in all tow risk patients (NPV=100%). ELISA optical density levels were significantly different between all riskgroups (P-values<0.01). In contrast, due to the tow positive predictive value (22%) and weak positive likelihood ratio (2.6), a positive ID-H/PF4 PaGIA (R) result did not considerably increase the probability of HIT. Conclusion: Our study confirms the combination of the 4T's score with the ID-H/PF4 PaGIA (R) as a reliable strategy to rule out HIT. Yet, confirming positive ID-H/PF4 PaGIA (R) results by flow cytometry within 1-2 h after blood sampling remains necessary. This novel clinical-laboratory approach can contribute in a rapid and reliable way to the definite diagnosis of HIT. (C) 2008 Elsevier Ltd. All rights reserved.