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From September 20 to 22, 2012, the scientific congress met in Nancy, France, to review the latest research on vitamin B12. Across several sessions, experts discussed the added utility of the active-B12 test. For optimal results, they suggested using it in conjunction with the MMA test, an approach we also support. Below are their main points.
Key Presentations
The application of serum holotranscobalamin, supported by methylmalonic acid as a front-line test to assess vitamin B12 status in a mixed patient population.
Assays for holotranscobalamin and MMA can be successfully utilized in tandem to define vitamin B12 status in large mixed patient populations. Initial automated screening by holotranscobalamin identifies an indeterminate cohort who benefit from confirmatory testing by MMA.
A. Sobczynska-Malefora (Nutristasis Unit, GSTS Pathology, London, UK)
Is HoloTC a more valuable biomarker of vitamin B12 intake and status?
These results support the conclusion that holoTC is a more sensitive biomarker of vitamin B12 status than the more traditional biomarker, serum total B12. HoloTC was more strongly correlated than serum total B12 to dietary intakes in both younger and older adults. HoloTC was able to detect small changes in vitamin B12 intake that were not detected by serum total B12.
CF Hughes (Northern Ireland Centre for Food and Health, University of Ulster)
HoloTC, the active B12.
HoloTC or Active-B12 denotes the part of circulating plasma cobalamin available for cells of the body. Current data supports holoTC as a promising biomarker for vitamin B12 status, both when holoTC is used alone or in combination with other biomarkers. Notably holoTC is the biomarker of choice in situations where measurement of total cobalamin is inadequate. During pregnancy total cobalamin declines despite a normal vitamin B12 status while holoTC remains unchanged. In children severely vitamin B12 deficient because of a lack of transcobalamin (total TC), total cobalamin may remain within the reference interval while no holoTC is detected. Finally, newly absorbed vitamin B12 occurs as holoTC, and therefore an increase in holoTC upon oral loading with vitamin B12 can be used to judge the capacity for uptake of the vitamin.
E. Nexo (Dept of Clinical Biochemistry, Aarhus University Hospital, Denmark)
MMA, Hcy and other metabolic markers of vitamin B12 deficiency.
Vitamin B12 deficiency is more widespread in the population than has been assumed so far. Measurement of total vitamin B12 has limited diagnostic sensitivity and specificity, especially in the concentration range <400pmol/L…..a lowered serum holoTC concentration (but normal MMA) is the earliest marker of vitamin B12 deficiency and signals that the body does not have sufficient available vitamin B12…Lowered holoTC combined with raised MMA and homocysteine levels are indicative of metabolically manifest vitamin B12 deficiency. The new markers enable the detection of vitamin deficiency notably more often.
W. Herrmann (Dept of Clinical Chemistry, Saarland University, Germany)