Hereditary thrombophilia in an unselected cohort of venous thrombosis patients in Singapore

AIM: Hereditary thrombophilic markers are commonly screened among patients diagnosed as having venous thromboembolism, but optimal patient selection and the goals of screening may differ between populations. Determining the patterns of hereditary thrombophilia may improve screening strategies. METHOD: An unselected cohort of venous thromboembolism patients in three tertiary institutions in Singapore was prospectively tested for the prevalence of deficiencies of protein C, protein S, antithrombin III, factor V Leiden and prothrombin 20210 gene mutations. RESULTS: Among 384 patients screened, the prevalences of protein S, protein C and antithrombin III were 9.20%, 1.18% and 4.19% respectively. Only one patient was positive for the factor V Leiden mutation and none tested positive for the prothrombin 20210 gene mutation. At least 1 in 9 patients (11.52%, 95% CI 8.20 to 15.93) will test positive for one of the above markers in an unselected group of 269 patients who completed all tests. The exclusion of patients with clinical risk factors did not improve the detection rates, in comparison with those with obvious provoking clinical risk factors (11.72%, 95% CI 7.36 to 18.06 vs 11.29%, 95% CI 6.73 to 18.18). When upper age limits were set for thrombophilia screening by decades, a statistical difference in the likelihood of a positive thrombophilia screen between younger and older patient was seen for patients below 40 (p<0.001). CONCLUSION: In Singapore and countries with similar demographics, hereditary thrombophilia screening should be confined to testing for protein C, protein S and antithrombin III.