Determination of serum holotranscobalamin concentrations with the AxSYM active B(12) assay: cut-off point evaluation in the clinical laboratory

A reliable early marker is required for diagnosis of cobalamin deficiency. We calculated an appropriate holotranscobalamin (HoloTC) cut-off point for identifying cobalamin deficiency using an immunoenzymatic assay. Determination of the cut-off threshold and correlation between HoloTC and the other diagnostic parameters routinely used for vitamin B(12) deficiency [total vitamin B(12) (tB(12)), folate, homocysteine] were measured in 250 routine blood specimens from 107 men (mean age 59.0+/-18.8 years) and 143 women (mean age 54.2+/-23.1 years). The inclusion criterion was serum tB(12) concentration