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

Vitamin B12 deficit is one of the most common vitamin deficiencies. However, there is no consensus on the cut-off points for vitamin B12 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 B12 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 B12', 'cobalamin', 'cut-off', 'deficiency' alone or in combinations. Broad ranges of cut-off points for vitamin B12 and its biomarkers were identified: vitamin B12 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 B12 and folate deficiency prevalences. We conclude that there is inconsistency in the literature regarding vitamin B12 cut-offs. It would be necessary to establish different reference cut-offs according to age, considering the analytical methods used.

B-vitamins and homocysteine in Spanish institutionalized elderly.

BACKGROUND: Hyperhomocysteinemia is an accepted risk factor for cardiovascular disease, and possibly also for cognitive impairment and dementia. It has also been proposed as a marker for the status of the B vitamins, which participate in the metabolism of homocysteine. Therefore, especially in the elderly, it is important to know the prevalence of high homocysteine (tHcy) levels and the influence that B vitamins have on them. MATERIAL AND METHODS: 218 elderly of both sexes, aged 60-105, living in an elderly home in Granada (Spain), were screened for serum folate, red blood cell (RBC) folate, serum cobalamin (B12) (Abbott, IMx), holotranscobalamin II (Holo-TC II) (HoloTC RIA, Axis-Shield), methylmalonic acid (MMA) (MS-GC), total pyridoxine (B6) (HPLC), and total homocysteine (tHcy) (Abbott, IMx). RESULTS: Hyperhomocysteinemia (tHcy >12 pmol/L) was detected in 80.7%. Serum folate deficiency was severe (< or =4 ng/mL) in 19.3% and moderate (4-7 ng/mL) in 43.1%. In 14.2% of the elderly RBC folate was < or =175 ng/mL, and in 61.0% it was between 175-400 ng/mL. Vitamin B12, measured in serum (< or =200 pg/mL), was deficient in 15.8%, but if measured as Holo-TC II (< or =45 pmol/L), deficiency ranged up to 39.1%. MMA was high (> or =300 nmol/L) in 45.6%. Vitamin B6 (< 20 nmol/L) was low only in one person. In order to identify the factors that could predict tHcy levels, a multiple regression analysis was performed. Best results corresponded to the combination of log serum folate and log Holo-TC II, which gave values of R > 0.5. If analyzed independently, the highest correlation was with log serum folate (r = -0.290), followed by RBC folate (r = -0.263), Holo-TC II (r = -0.228), log B12 (r = -0.175), and log B6 (r = -0.078). CONCLUSION: There is a high prevalence of vitamin B deficiency and hyperhomocysteinemia in the studied population. Our data confirm the influence of these vitamins, especially folate, on tHcy levels, but hyperhomocysteinemia cannot be used as the only diagnostic criterion to detect subclinical vitamin deficiency in elderly people, especially to detect vitamin B12 deficiency.