Low vitamin B-12 status in confirmed Alzheimer's disease as revealed by serum holotranscobalamin

OBJECTIVE: To examine the possible association of holotranscobalamin, the active fraction of serum cobalamin, with Alzheimer's disease. METHODS: 51 patients with pathologically confirmed Alzheimer's disease and 65 cognitively screened elderly controls were studied. Serum holotranscobalamin was measured by a new solid phase radioimmunoassay. RESULTS: Geometric mean levels showed no significant case-control differences for serum total cobalamin, but lower levels of holotranscobalamin in Alzheimer's disease (41.1 pmol/l) than in controls (57.1 pmol/l) (p < 0.001). The odds ratio of Alzheimer's disease was significant for low holotranscobalamin but not for low total cobalamin. CONCLUSIONS: Disturbed cobalamin status is common in Alzheimer's disease and accordingly measurement of holotranscobalamin should be considered in the assessment of cognitively impaired patients.