An audit of holotranscobalamin (“Active” B12) and methylmalonic acid assays for the assessment of vitamin B12 status: Application in a mixed patient population

Our results indicate that in the clinical setting a holoTC between 25 and 50 pmol/L is a poor predictor for the concentration of MMA provided the goal is to identify patients with MMA values above the limits used in the present study. Further studies are needed to evaluate to what extent holoTC < 25 and > 50 pmol/L reflect circulatory MMA concentrations.