Low plasma levels of vitamin B-6 are independently associated with a heightened risk of deep-vein thrombosis

Background-Elevated plasma levels of total homocysteine (tHcy) before and a fter an oral methionine load (PML) are associated with an elevated risk of deep-vein thrombosis (DVT). We investigated whether plasma levels of B vita mins that are involved in Hcy metabolism are associated with an elevated ri sk of DVT. Methods and Results-We compared 397 cases with previous DVT with 585 matche d healthy controls. The plasma levels of folate, vitamin B-12, vitamin B-6, and fasting and PML tHcy were measured. The ORs for DVT associated with hi gh (> 95th percentile) fasting levels and PML increases of tHcy were 2.1 (9 5% CI, 1.2 to 3.4) and 2.4 (95% CI, 1.5 to 3.9) after adjustment for establ ished risk factors for DVT. Fasting plasma levels and PML increases in tHcy correlated negatively with vitamin levels. The crude OR for folate levels in the lowest quartile compared with the highest was 1.5 (95% CI, 1.1 to 2. 1), and that for B-6 levels in the lowest and second quartiles compared wit h the highest was 1.5 (95% CI, 1.0 to 2.1). However, after adjustment for e stablished risk factors and fasting and PML tHcy, the ORs for B-6 levels in the lowest and second quartiles only remained statistically significant (l owest quartile: OR, 1.8; 95% Cl, 1.2 to 2.8, second quartile, OR, 1.9; 95% CI, 1.3 to 2.9). Conclusions-High fasting and PML tHcy and low vitamin B-6 plasma levels are associated with an elevated risk for DVT independently of established risk factors for DVT. The association of low vitamin B, levels with the risk fo r DVT is independent of fasting and PML tHcy levels.