HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: clinchem.2005.055509v1 51/11/2151    most recent Submit an electronic Letter to the Editor about this paper Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Bor, M. V. Articles by Nexo, E. Search for Related Content PubMed PubMed Citation Articles by Bor, M. V. Articles by Nexo, E. Related Collections Nutrition

Nonradioactive Vitamin B₁₂ Absorption Test Evaluated in Controls and in Patients with Inherited Malabsorption of Vitamin B₁₂

Mustafa Vakur Bor^1,2,a, Mualla Çetin³, Selin Aytaç³, Çidem Altay³ and Ebba Nexo¹

¹ Department of Clinical Biochemistry, NBG, AS, and² Department of Clinical Biochemistry, Aalborg Hospital, Aarhus University Hospital, Aarhus, Denmark.
³ Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey.

^aAddress correspondence to this author at: Department of Clinical Biochemistry, NBG, AS, Aarhus University Hospital, Norrebrogade 44, DK-8000 Aarhus C, Denmark. Fax 45-89493060; e-mail vakurbor{at}hotmail.com.

Background: Current tests for evaluation of vitamin B₁₂ absorption are problematic because they involve the use of radioactively labeled vitamin B₁₂. We describe a vitamin B₁₂ absorption test that circumvents this problem.

Methods: We measured cobalamin or transcobalamin saturated with cobalamin (holo-TC) 24 h after three 9-µg doses of vitamin B₁₂ given orally at 6-h intervals. We studied 17 patients with inherited malabsorption of vitamin B₁₂ attributable to Imerslund–Grasbeck syndrome (n = 13) or intrinsic factor deficiency (n = 4), their obligate heterozygous biological parents (n = 19), and healthy controls (n = 44).

Results: In the patients, the median (range) change of holo-TC after the B₁₂ load was not significant [1 (–42 to 5) pmol/L], nor was the change of cobalamin [–3 (–32 to 22) pmol/L], consistent with a lack of measurable active or passive absorption. In controls, however, the median (range) increases of holo-TC and cobalamin were 26 (–6 to 63) pmol/L and 41 (–37 to 109) pmol/L, respectively. Similarly, the parents showed increases of 23 (–2 to 47) pmol/L and 27 (–15 to 94) pmol/L. The mean areas under the ROC curves (95% confidence intervals) were 0.97 (0.93–1.0) for holo-TC and 0.87 (0.79–0.94) for cobalamin, distinguishing patients from controls. At a cutoff of 6 pmol/L for holo-TC, the diagnostic sensitivity (95% confidence interval) was 100 (81–100)%, and the diagnostic specificity was 92 (82–97)%.

Conclusion: Measurement of holo-TC after administration of vitamin B₁₂ is a promising approach for evaluating vitamin B₁₂ absorption.

The following articles in journals at HighWire Press have cited this article:

				R. Clarke, P. Sherliker, H. Hin, E. Nexo, A. M. Hvas, J. Schneede, J. Birks, P. M. Ueland, K. Emmens, J. M. Scott, et al. Detection of Vitamin B12 Deficiency in Older People by Measuring Vitamin B12 or the Active Fraction of Vitamin B12, Holotranscobalamin Clin. Chem., May 1, 2007; 53(5): 963 - 970. [Abstract] [Full Text] [PDF]

				K. M von Castel-Roberts, A. L. Morkbak, E. Nexo, C. A Edgemon, D. R Maneval, J. J Shuster, J. F Valentine, G. P. Kauwell, and L. B Bailey Holo-transcobalamin is an indicator of vitamin B-12 absorption in healthy adults with adequate vitamin B-12 status Am. J. Clinical Nutrition, April 1, 2007; 85(4): 1057 - 1061. [Abstract] [Full Text] [PDF]

				C. Carkeet, S. R. Dueker, J. Lango, B. A. Buchholz, J. W. Miller, R. Green, B. D. Hammock, J. R. Roth, and P. J. Anderson Human vitamin B12 absorption measurement by accelerator mass spectrometry using specifically labeled 14C-cobalamin PNAS, April 11, 2006; 103(15): 5694 - 5699. [Abstract] [Full Text] [PDF]

				J. W. Miller, M. G. Garrod, A. L. Rockwood, M. M. Kushnir, L. H. Allen, M. N. Haan, and R. Green Measurement of Total Vitamin B12 and Holotranscobalamin, Singly and in Combination, in Screening for Metabolic Vitamin B12 Deficiency Clin. Chem., February 1, 2006; 52(2): 278 - 285. [Abstract] [Full Text] [PDF]