# Clinical utility and costs of inpatient hereditary thrombophilia testing following acute VTE: A 5-Year retrospective study

## TL;DR

This study found that inpatient hereditary thrombophilia testing after blood clots is common but rarely changes treatment and is costly.

## Contribution

The study provides empirical evidence on the limited clinical utility and high costs of inpatient thrombophilia testing after acute VTE.

## Key findings

- 19.6% of thrombophilia tests were abnormal, but most did not alter patient management.
- Testing costs were high ($385,161 in institutional charges) with minimal clinical impact.
- Younger patients and those with unprovoked VTE were not more likely to have positive results.

## Abstract

Hereditary thrombophilia testing is frequently ordered after venous thromboembolism (VTE), despite little evidence of clinical utility and most guidelines cautioning against testing. We conducted a retrospective, observational study of inpatient hereditary thrombophilia testing ordered during a hospital admission for acute VTE between 2019 and 2024. We aimed to characterize patterns of testing results, and costs, and to evaluate whether younger patients and those with unprovoked VTE were more likely to test positive for hereditary thrombophilia. A total of 835 hereditary thrombophilia tests – including those for factor V Leiden, prothrombinG20210A, deficiencies of protein S, protein C, and antithrombin, hyperhomocysteinemia, and plasminogen activator inhibitor-1 excess – were ordered in 220 patients. Overall, 19.6% of results were abnormal, and 45.0% of patients had at least one abnormal result. There was no difference in the rate of positive results among patients with provoked vs. unprovoked VTE (30.7% vs. 34.5%, p = .554) nor patients < 50 vs. ≥ 50 years of age (33.1% vs. 32.4%, p = .912). Only 4/99 (4.0%) patients with an abnormal result had their clinical management clearly changed due to the result. The tests totaled $385,161 USD in institutional charges and $26,029 USD in Medicare fees. Inpatient hereditary thrombophilia testing during admission for acute VTE is low yield, with frequent abnormal results, many of which likely represented false positives, and minimal impact on clinical management with high costs.

Thrombophilia testing following acute venous thromboembolism was commonly performed at an academic medical center with high associated costs, and nearly 20% of tests were abnormal.Many results were below the limits of normal for the assay, but higher than expected in congenital deficiency, likely indicating false positives.Young patients and those with unprovoked venous thromboembolism were not more likely to have positive test results.Clinical management rarely changed in response to a positive result, indicating low value of testing in the inpatient setting.Prospective studies with long-term outpatient follow-up would help determine the optimal timing of thrombophilia testing.

Thrombophilia testing following acute venous thromboembolism was commonly performed at an academic medical center with high associated costs, and nearly 20% of tests were abnormal.

Many results were below the limits of normal for the assay, but higher than expected in congenital deficiency, likely indicating false positives.

Young patients and those with unprovoked venous thromboembolism were not more likely to have positive test results.

Clinical management rarely changed in response to a positive result, indicating low value of testing in the inpatient setting.

Prospective studies with long-term outpatient follow-up would help determine the optimal timing of thrombophilia testing.