Performance of a new, rapid, automated immunoassay for the detection of anti-platelet factor 4/heparin complex antibodies.

Heparin-induced thrombocytopenia (HIT) is a life-threatening adverse reaction to heparin that must be identified quickly to determine appropriate anticoagulant therapy strategies. The most common antibodies involved in HIT are directed against platelet factor 4/heparin (PF4/H) complexes. Many methods for anti-PF4/H detection exist such as enzyme immunoassays (EIAs), which have been shown to exhibit high-negative predictive value allowing for the exclusion of HIT in the majority of suspected patients; however, most EIAs are performed in a batch mode, thereby delaying results to the physician. HemosIL HIT-Ab(PF4-H) is a new, rapid method for the detection of total immunoglobulin against PF4/H complexes on ACL TOP Family systems. The assay was evaluated in a multicentre study at three sites with 414 HIT-suspected patients. Using a cut-off value of 1.0 U/ml for HemosIL HIT-Ab(PF4-H), the new test was compared with Asserachrom HPIA. Results showed a co-positivity of 60.2% [95% confidence interval (CI) 48.9-70.8], co-negativity of 94.6% (95% CI 91.5-96.7), and overall agreement of 87.7% (95% CI 84.1-90.7). These results are comparable to other PF4/H antibody assays available; with the added benefit of full automation and on-demand testing which provides results at the critical moment when physicians are required to make clinical decisions regarding anticoagulant therapy.