194 The Impact of Prospective Review of Platelet Factor 4 Testing Practices for Suspected Heparin-Induced Thrombocytopenia: An Antithrombotic Stewardship Initiative

Introduction: Heparin-induced thrombocytopenia (HIT) is a life-threatening form of immune-thrombocytopenia caused by antibodies against the heparin-platelet factor 4 (PF4) complex. The PF4 assay is the recommended first step for laboratory testing in patients at intermediate to high risk for HIT. The PF4 has excellent sensitivity but low specificity and a high rate of false positive results which can lead to initiation of unnecessary and costly treatments. Mitigation of inappropriate HIT testing in patients with low HIT probability is an important antithrombotic stewardship initiative to improve patient safety, reduce treatment costs, and reduce laboratory technician staff workload.