Background: Routine thrombophilia testing is controversial because of the low yield of positive tests, costs involved, and debate about the clinical usefulness of the data obtained from testing. Laboratory investigations are rarely done for those with superficial venous thrombosis (SVT) or isolated calf vein thrombosis (CVT) which are often not treated with anticoagulants.
Objective: To identify the incidence of markers of thrombophilia in patients with deep vein thrombosis (DVT), SVT, isolated CVT or a history of thrombosis in a referral practice.
Methods: One hundred and sixty-six patients were referred to our thrombosis unit for consultation, including patients with SVT, DVT, and preoperative patients with a previous history of SVT or DVT. Patients underwent thrombophilia screening and patients with a diagnosis of SVT or DVT were confirmed by bilateral duplex ultrasonography of all lower limb veins. Thrombophilia testing included factor V Leiden (FVL), prothrombin 20210A mutation (P2), methylene tetrahydrofolate reductase deficiency (MTHFR), fasting serum homocysteine (HC), lupus anticoagulant (LA), anticardiolipin antibodies (ACA), antithrombin deficiency (AT), protein S deficiency (PS), and protein C deficiency (PC).
Results: The incidence of any significant abnormality in patients with DVT was 27/44 (61%; 95% Confidence interval [CI], 47-76%) and 10 of these patients were positive for FVL (23%; 95% CI, 10-35%). Twelve patients with isolated CVT were seen and five had at least one abnormality (42%; 95% CI, 14-70%) including one with FVL (8%; 95% CI, 0-24%). Thirty-nine patients with isolated SVT were seen including 14 with at least one abnormality (36%; 95% CI, 21-51%) and five of these patients with SVT had FVL (13%; 95% CI, 2-23%). Nine patients with recurrent DVT were seen and five of these had at least one abnormal test (56%; 95% CI, 23-88%). Finally, 18 of the 166 patients had more than one abnormality (11%; 95% CI, 6-16%).
Conclusion: The presence of one or more markers of thrombophilia was significantly higher in this patient population compared to reports from other centres. This study identified 18/166 (10.8%; 95% CI, 6-16%) with more than one defect where life-long anticoagulation might be considered. The results in this subset of patients as well as the serious defects found in some patients with provoked DVT, isolated CVT or isolated SVT demonstrate the value of this screening program to both these patients and their blood relatives. On the other hand, this is a small series from a referral practice where the incidence of these defects is greater than one would expect in the general population. These studies are preliminary and it is not recommended that all VTE patients should be screened on the basis of the current report.