Inappropriate use of protein C, protein S, and antithrombin testing for hereditary thrombophilia screening: an experience from a large university hospital

Abstract

Deficiencies of protein C, protein S, and antithrombin are the main inherited risk factors in Thai patients with venous thromboembolism, although the prevalence is not high. To evaluate the appropriate use of the testing for these proteins, the test orders of 503 patients were retrospectively reviewed using the proposed guidelines. Inter-rater reliability between two investigators was also calculated. Of 503, 459 (91%; 95% confidence interval 88-93%) of the test orders were inappropriate. The most common cause of inappropriateness was testing during acute thrombosis (42.5%). Results were inconclusive in 105 (20.9%) patients who had isolated decrease in one of the proteins, mostly owing to lack of confirmation of the abnormal results. Kappa index for the reliability of two investigators was 0.79. To enhance the appropriate use of hereditary thrombophilia screening tests, physician education concerning the patient selection, suitable timing for testing and repetition of the tests with abnormal results should be emphasized.