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23-08-2011 | Cardiology | Article

Thrombophilia screening should be population-specific

Abstract

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MedWire News: Thrombophilia screening should be restricted to testing for protein C, protein S, and antithrombin III deficiencies in people from Singapore and countries with similar demographics, researchers report.

"A diagnosis of venous thromboembolism (VTE) can trigger a slew of investigations directed at identifying pre-existing risk factors for VTE," explain Hen Joo Ng (Singapore General Hospital) and colleagues.

"Hereditary thrombophilic markers inherently become included as part of this work-up in a significant proportion of patients. Unfortunately, thrombophilia screening will likely only benefit select groups of patients," they add.

Determining the patterns of hereditary thrombophilia may improve screening strategies, the researchers remark.

Ng and team therefore prospectively tested 384 patients with VTE for the prevalence of protein C, protein S, and antithrombin III deficiencies, and factor V Leiden and prothrombin 20210 gene mutations.

They report that the prevalence of protein S, protein C, and antithrombin III deficiencies was 9.2%, 1.2%, and 4.2% respectively.

By contrast, just one patient, who was of Caucasian ancestry, had the factor V Leiden mutation, and none were carriers of the prothrombin 20210 gene mutation.

The researchers note that international consensus guidelines on thrombophilia testing commonly recommend against testing older patients and patients with strong provoking risk factors for VTE.

To see whether this is justified, Ng et al performed a subgroup analysis among 269 of the patients who received screening for all five thrombophilias.

They found that when all patients were screened, 11.5% were positive for at least one of the thrombophilic markers. Similar results were observed when the team divided the patients into those with and without provoking risk factors, with detection rates of 11.3% and 11.7%, respectively.

"Hence, the presence of an obvious VTE-provoking factor may not necessarily preclude patients from being screened," the authors write in the Journal of Clinical Pathology.

By contrast, age was a better discriminator of patients with hereditary thrombophilias. More specifically, patients aged 40 years and younger were significantly more likely to be positive for a hereditary defect compared with the unselected population, with rates of 24.1% and 11.5%, respectively.

Ng and co-authors point out that the prevalence of protein S and antithrombin III deficiencies in their cohort was similar to those reported among Thai and Chinese cohorts.

"Based on our findings, we would recommend testing for only protein C, protein S, and antithrombin III [in this population]," they write.

"Our factor V Leiden and prothrombin 20210 screening results affirm the stand that there is little justification to test for these markers among patients drawn from an Asian population with a predominantly Mongoloid ancestry," the team concludes.

By Laura Dean

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