A review of the cut-off points for the diagnosis of vitamin B12 deficiency in the general population

Vitamin B deficit is one of the most common vitamin deficiencies. However, there is no consensus on the cut-off points for vitamin B and its co-markers, such as folate, holotranscobalamin, methylmalonic acid and homocysteine. In order to establish the state of the art about cut-off points used to determine vitamin B deficiency in the last decades, the database MEDLINE was used for searching studies published in adults between December 1992 and May 2014 (69 articles), using search terms like ‘vitamin B ’, ‘cobalamin’, ‘cut-off’, ‘deficiency’ alone or in combinations. Broad ranges of cut-off points for vitamin B and its biomarkers were identified: vitamin B ranged between 100 pmol/L and 350 pmol/L, holotranscobalamin 20–50 pmol/L, methylmalonic acid 0.210–0.470 μmol/L, homocysteine 10–21.6 μmol/L, serum folate 3.7–15.9 nmol/L and red blood cell 124–397 nmol/L. For the majority of studies, the potential influence of age, analytical methods, gender and fortified food consumption was not taken in account when choosing cut-off values. This could explain the discrepancies between studies on vitamin B and folate deficiency prevalences. We conclude that there is inconsistency in the literature regarding vitamin B cut-offs. It would be necessary to establish different reference cut-offs according to age, considering the analytical methods used.