MTHFR and the risk for cerebral venous thrombosis- a meta-analysis

Background: The association between methylenotetrahydrofolate reductase (MTHFR) 677TT and the increased risk of venous thrombosis is uncertain. Studies of this polymorphism in cerebral venous thrombosis (CVT) are inconclusive. Objectives: With a systematic review, we aimed to collect all case-control studies comparing the frequency of this polymorphism in CVT patients (cases) and healthy controls. Methods: We used the MEDLINE, Cochrane Library and the ISI web of knowledge electronic databases and reference lists of retrieved articles in order to identify published case-control studies that evaluated the presence of MTHFR 677C>T polymorphism in CVT. Two reviewers independently selected studies. We compared the frequency of 677TT between cases and controls using the Mantel-Haenszel method, a fixed and a random-effects model in the pooled data. Results: Nine case-control studies were included. The pooled analysis included 382 patients with CVT and 1217 controls. The frequency of 677TT genotype among CVT patients was not significantly higher compared with controls (15.7% versus 14.6%; OR=1.12, 95% confidence interval (95% CI) 0.80 to 1.58; p=0.50). There was significant heterogeneity between studies. Conclusions: This meta-analysis confirmed that there is currently insufficient data supporting that 677TT genotype is a risk factor for CVT. These results imply a continuing searching for the cause of CVT in patients with this polymorphism. (C) 2009 Elsevier Ltd. All rights reserved.