Abstract
Introduction
Testing for thrombophilic risk factors is common in patients with thrombosis. However, inpatient hereditary thrombophilia work-ups are prone to false-positive and false-negative results due to concurrent acute phase changes, protein consumption, anticoagulation therapy, and liver disease. A recent ASCP Choosing Wisely guideline recommends against measuring protein C (PC), protein S (PS), or antithrombin III (AT3) to diagnose a hereditary deficiency during an active clotting event.
We aimed to review inpatient PC, PS, and AT3 activity assay ordering practices at a tertiary care center. The goal of this study was to determine appropriateness and identify areas for improvement in inpatient thrombophilia ordering practices.
Methods
A retrospective review of inpatients who underwent thrombophilia testing was performed. Inclusion criteria consisted of adult inpatients with PC, PS, and/or AT3 activity results. Patients for whom AT3 was ordered alone were excluded. The timeframe of testing relative to an acute thrombotic event, anticoagulation therapy, and liver disease was determined via electronic medical record review. Other conditions that can affect PC, PS, or AT3 levels were recorded if noted.
Results
Over 5 months, 50 inpatients underwent testing for PC, PS, and/or AT3. Testing was performed within 2 weeks of an acute thrombotic event in 92% of patients; 32% received anticoagulation therapy prior to testing and 16% had liver disease. Test results below the reference range were found in the following percentage of patients: 16% PC, 34% PS, and 16% AT3. In total, 23 of 50 (46%) patients had one or more abnormal results; all 23 had potential confounding conditions/drug.
Conclusions
Inpatient PC, PS, and AT3 testing was frequently performed in clinical settings, which may cause false-positive or false-negative results. This demonstrates the need for increased education and dialogue between the laboratory and clinicians to improve test utilization practices. Potential interventions are currently being analyzed.
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