Homocysteine Study (HOST)

Overview

The primary objective of this study is to test the hypothesis that administration of folate, pyridoxine (vitamin B6) and cyanocobalamin (vitamin B12) in high doses to patients with advanced chronic renal failure or end stage renal disease and abnormally high plasma homocysteine levels will lower the homocysteine levels and the death rate compared to patients who receive placebo. The secondary objective is to test the hypothesis that intake of the vitamins compared to placebo decreases the incidence of myocardial infarction, disabling stroke, and amputation of a lower extremity and, in hemodialysis patients, thrombosis of the vascular access.

Primary Hypothesis: The primary objective of this proposal is to test the hypothesis that administration of folate, pyridoxine (vitamin B6) and cyanocobalamin (vitamin B12) in high doses to patients with advanced chronic renal failure or end-stage renal disease and abnormally high plasma homocysteine levels will lower the homocysteine levels and increase survival. Secondary Hypotheses: The secondary objectives are to test the hypotheses that intake of the vitamins decreases: 1) MI, 2) stroke, 3) amputation of lower extremity, 4) combination death, MI, stroke and amputation of lower extremity, 5) thrombosis of the vascular access in hemodialysis patients. Primary Outcome: Death Interventions: A treated group that receives a daily tablet containing 40mg of folic acid, 100mg of pyridoxine and 2mg of B12 versus a control group that receives a placebo. Study Abstract: The experimental design is a prospective, two-arm, randomized, double blind study, stratified for medical center and whether the patient has chronic renal failure or end-stage renal disease. In each arm 1003 patients will ingest daily a capsule containing either 40mg of folic acid, 100mg of pyridoxine and 2mg of vitamin B12, or placebo. We will use stratified randomization to ensure that the treatment is balanced within the end-stage renal disease patients and chronic renal failure patients. This 6 year study will require an accrual phase of 2 years and a treatment phase lasting a minimum of 4 years. Patients will be screened by their plasma homocysteine concentration. They must have a level of at least 15 uM/L to be enrolled in the study. The study nurse will evaluate each patient at 3 months. Thereafter, patients will be contacted by phone, or mail if they prefer, at 3-month intervals by coordinators at a central location. Secondary endpoint events, hospitalization, onset of dialysis, and death or other reason for exit from the study will be recorded on standard forms. Plasma homocysteine levels will be obtained at 3 months in all patients. Patients will be excluded if: age less than 21 years, expected life span less than 6 months, pregnancy, metastatic cancer, AIDS-related infection, end-stage liver disease, vitamin B12 deficiency, treatment with methotrexate, or anticonvulsants, unreliable or likely non-compliant, participation in other long-term trial, or unwilling or unable to give informed consent. For a relative treatment effect of 17% (that is reducing the 3-year death rate from 28% to 23.2%) and 80% power, 2006 patients and 36 VA medical centers are required. An abundance of published reports has shown a strong correlation between homocysteinemia and the incidence of cardiovascular death. Authors of these papers have unanimously recommended a study be undertaken to determine if folate, pyridoxine, and vitamin B12 can lower the incidence. The study is to be conducted in patients with chronic renal failure and end-stage renal disease whose plasma homocysteine levels and incidence of cardiovascular death and disease are among the highest of all patient populations. By screening for patients with high plasma homocysteine concentrations and measuring the levels after 3 months, we will be able to determine if the hypothetical reduction in death and cardiovascular event rate is associated with a decrease in plasma homocysteine concentration.