What level of plasma homocyst(e)ine should be treated?

High levels of plasma homocyst(e)ine (H[e]) are associated with increased vascular risk. Treatment is being contemplated, but the level at which patients should be treated is not known. We compared the response of carotid plaque to vitamin therapy in patients with H(e) above and below 14 μmol/L, a level commonly regarded as high enough to warrant treatment. Two-dimensional B-mode ultrasound measurement of carotid plaque was used to assess the response to vitamin therapy with folic acid 2.5 mg, pyridoxine 25 mg, and cyanocobalamin 250 μg daily, in 101 patients with vascular disease (51 with initial plasma levels above, and 50 below 14 μmol/L). Among patients with plasma H(e) 14 μmol/L, the rate of progression of plaque area was 0.21 ± 0.41 cm2/year before vitamin therapy, and −0.049 ± 0.24 cm2/year after vitamin therapy (P2 = .0001; paired t test). Among patients with levels