Plasma holotranscobalamin compared with plasma cobalamins for assessment of vitamin B12 absorption; optimisation of a non-radioactive vitamin B12 absorption test (CobaSorb).
BACKGROUND
A recently developed non-radioactive vitamin B(12) absorption test (CobaSorb) was further explored to identify the best marker for reflection of vitamin B(12) absorption and to determine the duration of the test.


METHODS
Seventy-eight healthy individuals (age 21-81 years) were given three oral doses of 9 microg vitamin B(12) per day for 5 successive days. Non-fasting blood samples were collected on days 1 to 5 before administration of vitamin B(12) and on day 8. Cobalamins and holotranscobalamin were measured.


RESULTS
Performance of the vitamin B(12) absorption test was evaluated in individuals with holotranscobalamin or cobalamins below the 75% percentiles. We used a change greater than 2xCV(day-to-day) in holotranscobalamin (22%) and cobalamins (12%) to indicate a change caused by absorption of vitamin B(12). Among individuals with a baseline holotranscobalamin below the 75% percentile (<75 pmol/L, n=57), 98% had an increase in holotranscobalamin >22% from day 1 to day 3. In contrast, only 72% of the individuals with baseline cobalamins below the 75% percentile (<335 pmol/L, n=57) had an increase in cobalamins >12%.


CONCLUSIONS
In healthy individuals with baseline holotranscobalamin <75 pmol/L, vitamin B(12) absorption is well reflected by an increase in holotranscobalamin after 2 days administration of oral vitamin B(12).
Hvas
Anne-Mette
AM
Department of Clinical Biochemistry, Skejby Hospital, Aarhus University Hospital, 8000 Aarhus, Denmark.
Morkbak
Anne L
AL
Nexo
Ebba
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D001774:Blood Chemical Analysis / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D011868:Radioisotopes / Q000737:chemistry; D014155:Transcobalamins / Q000032:analysis* / Q000493:pharmacokinetics; D014805:Vitamin B 12 / Q000097:blood* / Q000378:metabolism / Q000493:pharmacokinetics
D015415:Biomarkers; D011868:Radioisotopes; D014155:Transcobalamins; D014805:Vitamin B 12