P8. Abstract Title: Inpatient Inherited Thrombophilia Testing a Multicenter Retrospective Review of Practice Patterns and Indications

Abstract

<h3>Background</h3> Hereditary thrombophilia testing identifies genetic conditions that can predispose patients to an increased risk of venous thromboembolism (VTE); these conditions include Factor V Leiden, Factor II G20210A gene mutation, protein C deficiency and protein S deficiency. Testing as an inpatient can be challenging as acute thrombosis and anticoagulation can confound the study results. As a result, major society guidelines do not recommend routine hereditary thrombophilia testing in an acute setting. <h3>Objective</h3> The purpose of this study is to retrospectively review the ordering patterns and outcomes of hereditary thrombophilias in inpatients. <h3>Methods</h3> All hereditary thrombophilias ordered for inpatients between May 2016 to April 2019 at four major academic centers, Foothills Medical Centre, Peter Lougheed Centre, South Health Campus and Rockyview General Hospital in Calgary, Alberta were retrospectively reviewed. The primary outcome was the indication for thrombophilia testing and the results of the testing. Secondary outcomes included patient demographics and thrombosis risk factors. <h3>Results</h3> 428 patients were identified as having had hereditary thrombophilia testing as inpatients. 411 patients had a documented thrombotic event with 400 patients (93.4%) having an event within 30 days of their testing. 287 patients (69%) were on anticoagulation at the time. 60.1% of patients had a venous thrombosis, with pulmonary embolism being the most common (28.2%) while 39.9% of patients had an arterial thrombosis with 19% being a stroke. 177 (43%) of patients had another provoking risk factor at the time of their thrombosis, including malignancy, recent major surgery, pregnancy and exogenous estrogen use. The majority of testing was ordered by General internal medicine (30.1%) and neurology (25%). Only 3.9% of patients had hematology involvement at the time of their testing. 77 (18%) patients had a positive thrombophilia screen with heterozygous Factor V Leiden (11.4%) and heterozygous Factor II G20210A (5.1%) variant being the most common. Prior VTE was associated with an increased likelihood of a positive thrombophilia result (RR 2.15, CI 1.43-3.23, p=0.0002) but family history, arterial thrombosis, and venous thrombosis at unusual sites were not. <h3>Conclusion</h3> The utility of hereditary thrombophilia testing is limited in an inpatient setting, particularly for patients with acute thrombosis and on anticoagulation. The majority of tests were ordered inappropriately and resulted in unnecessary costs to the healthcare system. This study indicates the need for further interventions to improve physician education and adherence to guidelines.