Quantification of Holo-Transcobalamin, a Marker of Vitamin B12 Deficiency
Ebba Nexo1a, Anna-Lisa Christensen1, Anne-Mette Hvas1, Torben E. Petersen2 and Sergey N. Fedosov2
1 Department of Clinical Biochemistry, Aarhus University Hospital, DK-8000 Aarhus C, Denmark fax 45-8949-3060, e-mail E.Nexo@dadlnet.dk)

We report a new method for measurement of holo-transcobalamin (holoTC), in which magnetic beads coated with vitamin B12 (cobalamins) precipitate apo-transcobalamin (apoTC) and the holoTC present in the supernatant is measured by ELISA.

Serum holoTC denotes the part of vitamin B12 accessible for the cells of the body and is considered to be a sensitive marker of vitamin B12 deficiency. Serum holoTC is not easily measured because it accounts for only approximately one-third of the circulating vitamin B12 and because the major part of TC circulates unsaturated with vitamin B12 (apoTC). In the few published attempts to measure holoTC, TC is separated from the other vitamin B12-binding protein, haptocorrin, before quantification of vitamin B12. This allows a direct measurement of the cobalamins attached to TC or an indirect calculation of holoTC from measurement of total plasma cobalamins and the plasma cobalamins not attached to TC. We have chosen another path………(report truncated).

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