[Diagnosis of vitamin B12 deficiency--time for reflection]

Since plasma methylmalonic acid (MMA) was introduced in Denmark in 1992 both MMA and P-cobalamins have been increasingly employed to diagnose vitamin B-12 deficiency, and the consumption of vitamin B-12 has been almost doubled during the same period. The controversy about diagnosing vitamin B-12 deficiency is reflected in a huge geographical variation both in requisition of MMA and P-cobalamins and in the vitamin B-12 consumption. On the basis of studies performed so far we conclude that MMA is a reliable method with a good nosographic sensitivity. However, the nosographic specificity is sparsely examined, and the evidence to use MMA as a primary test for diagnosing vitamin B-12 deficiency is still insufficient. We recommend P-cobalamins as the first line test, and if P-cobalamins are in the grey area 125-250 pmol/l we recommend supplementation with MMA. For patients who also have an MMA in the grey area (0.29-0.75 mumol/l) we recommend that the patient is re-examined after about a year.