Biochemical markers of vitamin B12 deficiency combined in one diagnostic parameter: the age-dependence and association with cognitive function and blood hemoglobin.

BACKGROUND

Vitamin B12 deficiency is diagnosed by measurements of total B12, holo-transcobalamin (holoTC), methylmalonic acid (MMA) and total homocysteine (Hcy) in blood. Results of the individual biochemical tests are often contradictory. Here the four markers are combined to achieve a more reliable indication of the B12 status. The results are aligned with hemoglobin and cognitive score.

METHODS

Databases from the literature were plotted in coordinates x=(holoTC·B12)(1∕2), y=1∕2·log10(MMA·Hcy), where distribution of points revealed the subgroups characterized by logarithmic ratios lr=log10[(holoTC·B12)/(MMA·Hcy)]. Distance between the subgroups w=lr(Test)-lr(Normal) was taken as a robust biochemical indicator of B12 status ("wellness parameter").

RESULTS

The dependence of lr(Normal) vs. age was described by a mathematical function to correct parameter w. The B12 status was defined as "excellent" (w≈+0.4), "normal" (w≈0), "transitional" (w≈-0.5), "deficient" (w≈-1.7) and "pernicious" (w≈-3.0). The groups of individuals with either w≥0 or w≤-1 exhibited the statistically significant differences in both hemoglobin and cognitive score. Analogous assessment of B12 status by the individual markers agreed with only one out of two physiological characteristics.

CONCLUSION

Combined parameter w is a reliable diagnostic tool.