Utility of measuring vitamin B12 and its active fraction, holotranscobalamin, in neurological vitamin B12 deficiency syndromes

Background: Decreased vitamin B12 (cobalamin) status has been associated with various neurolopsychiatric conditions, such as peripheral neuropathy, subacute combined degeneration, affective disorders and cognitive impairment. Current assays analyze total vitamin B12 concentration, of which only a small percentage is metabolically active. Measurement of its active fraction, holotranscobalamin (holoTC), might be of greater relevance for detecting vitamin B12 deficiency, but data in neuropsychiatric populations are lacking. Objective: To validate total vitamin B12 and holoTC serum levels for the detection of vitami…