Plasma Holotranscobalamin as Compared to Plasma Cobalamins for Assessment of Vitamin B12 Absorption. Optimisation of a Non-Radioactive Vitamin B12 Absorption Test (CobaSorb)

In the present study the design of the vitamin B12 absorption test, CobaSorb, is further optimised. We investigate which test - measurement of holotranscobalamin or cobalamins - could be used for reflection of vitamin B12 absorption. Furthermore, we prolong the duration of vitamin B12 administration in order to determine the final duration of the vitamin B12 absorption test CobaSorb.

Seventy-eight healthy individuals (age 21-81 years) are treated with three oral doses of 9 microgram cyanocobalamin per day for five successive days. Non-fasting blood samples are collected on day 1-5 before administration of the first dose of vitamin B12 and on day 8. Cobalamins and holotranscobalamin are measured on day 1-5 and 8. The performance of the vitamin B12 absorption test will be evaluated in individuals with borderline or low levels of holotranscobalamin or cobalamins (below the 75% percentiles) using a change larger than 2CV(day to day) of holotranscobalamin (22%) and cobalamins (12%) to indicate a change caused by absorption of the administered vitamin B12.