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1
Axis-Shield ASA, Ulvenveien 87, PO Box 206 Økern, N-0510 Oslo, Norway.
2
Division of Hematology/Oncology, State University of New York, Health Science Center, Brooklyn, NY 11203.
3
Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Science Park, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
aAuthor for correspondence. Fax 47-22700-770; e-mail lars.orning{at}no.axis-shield.com.
Background: Only cobalamin carried by transcobalamin (holo-transcobalamin) is available for cellular uptake and hence is physiologically relevant. However, no reliable or accurate methods for quantifying holo-transcobalamin are available. We report a novel holo-transcobalamin assay based on solid-phase capture of transcobalamin.
Methods: A monoclonal antibody specific for human transcobalamin with an affinity constant >1010 L/mol was immobilized on magnetic microspheres to capture and concentrate transcobalamin. The cobalamin bound to transcobalamin was then released and assayed by a competitive binding radioassay. The quantification of holo-transcobalamin was accomplished using calibrators composed of recombinant, human holo-transcobalamin.
Results: The assay was specific for holo-transcobalamin and had a detection limit of 5 pmol/L. Within-run and total imprecision (CV) was 5% and 8–9%, respectively. The working range (CV <20%) was 5–370 pmol/L. Dilutions of serum were linear in the assay range. The recovery of recombinant, human holo-transcobalamin added to serum was 93–108%. A 95% reference interval of 24–157 pmol/L was established for holo-transcobalamin in 105 healthy volunteers 20–80 years of age. For 72 of these sera, holo-haptocorrin and total cobalamin were also determined. Whereas holo-haptocorrin correlated well (r2 = 0.87) with total cobalamin, holo-transcobalamin correlated poorly (r2 = 0.23) with total cobalamin or holo-haptocorrin.
Conclusions: The solid-phase capture assay provides a simple, reliable method for quantitative determination of holo-transcobalamin in serum.
The following articles in journals at HighWire Press have cited this article:
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  M. G. Garrod, R. Green, L. H. Allen, D. M. Mungas, W. J. Jagust, M. N. Haan, and J. W. Miller Fraction of Total Plasma Vitamin B12 Bound to Transcobalamin Correlates with Cognitive Function in Elderly Latinos with Depressive Symptoms Clin. Chem., July 1, 2008; 54(7): 1210 - 1217. [Abstract] [Full Text] [PDF]
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J. Brady, L. Wilson, L. McGregor, E. Valente, and L. Orning Active B12: A Rapid, Automated Assay for Holotranscobalamin on the Abbott AxSYM Analyzer Clin. Chem., March 1, 2008; 54(3): 567 - 573. [Abstract] [Full Text] [PDF]
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R. Obeid, M. Kasoha, J.-P. Knapp, P. Kostopoulos, G. Becker, K. Fassbender, and W. Herrmann Folate and Methylation Status in Relation to Phosphorylated Tau Protein(181P) and {beta}-Amyloid(1-42) in Cerebrospinal Fluid Clin. Chem., June 1, 2007; 53(6): 1129 - 1136. [Abstract] [Full Text] [PDF]
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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]
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 S. J Eussen, L. C de Groot, L. W Joosten, R. J Bloo, R. Clarke, P. M Ueland, J. Schneede, H. J Blom, W. H Hoefnagels, and W. A van Staveren Effect of oral vitamin B-12 with or without folic acid on cognitive function in older people with mild vitamin B-12 deficiency: a randomized, placebo-controlled trial. Am. J. Clinical Nutrition, August 1, 2006; 84(2): 361 - 370. [Abstract] [Full Text] [PDF]
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R. Obeid, A. L. Morkbak, W. Munz, E. Nexo, and W. Herrmann The Cobalamin-Binding Proteins Transcobalamin and Haptocorrin in Maternal and Cord Blood Sera at Birth Clin. Chem., February 1, 2006; 52(2): 263 - 269. [Abstract] [Full Text] [PDF]
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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]
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H. Refsum, C. Johnston, A. B. Guttormsen, and E. Nexo Holotranscobalamin and Total Transcobalamin in Human Plasma: Determination, Determinants, and Reference Values in Healthy Adults Clin. Chem., January 1, 2006; 52(1): 129 - 137. [Abstract] [Full Text] [PDF]
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K. M von Castel-Dunwoody, G. P. Kauwell, K. P Shelnutt, J. D Vaughn, E. R Griffin, D. R Maneval, D. W Theriaque, and L. B Bailey Transcobalamin 776C->G polymorphism negatively affects vitamin B-12 metabolism Am. J. Clinical Nutrition, June 1, 2005; 81(6): 1436 - 1441. [Abstract] [Full Text] [PDF]
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 S. J. P. M. Eussen, L. C. P. G. M. de Groot, R. Clarke, J. Schneede, P. M. Ueland, W. H. L. Hoefnagels, and W. A. van Staveren Oral Cyanocobalamin Supplementation in Older People With Vitamin B12 Deficiency: A Dose-Finding Trial Arch Intern Med, May 23, 2005; 165(10): 1167 - 1172. [Abstract] [Full Text] [PDF]
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W. Herrmann, H. Schorr, R. Obeid, J. Makowski, B. Fowler, and M. K. Kuhlmann Disturbed Homocysteine and Methionine Cycle Intermediates S-Adenosylhomocysteine and S-Adenosylmethionine Are Related to Degree of Renal Insufficiency in Type 2 Diabetes Clin. Chem., May 1, 2005; 51(5): 891 - 897. [Abstract] [Full Text] [PDF]
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B. Riedel, A.-L. B. Monsen, P. M. Ueland, and J. Schneede Effects of Oral Contraceptives and Hormone Replacement Therapy on Markers of Cobalamin Status Clin. Chem., April 1, 2005; 51(4): 778 - 781. [Full Text] [PDF]
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X. Chen, A. F Remacha, M P. Sarda, and R. Carmel Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II Am. J. Clinical Nutrition, January 1, 2005; 81(1): 110 - 114. [Abstract] [Full Text] [PDF]
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M. V. Bor, E. Nexo, and A.-M. Hvas Holo-Transcobalamin Concentration and Transcobalamin Saturation Reflect Recent Vitamin B12 Absorption Better than Does Serum Vitamin B12 Clin. Chem., June 1, 2004; 50(6): 1043 - 1049. [Abstract] [Full Text] [PDF]
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H. Refsum, A. D. Smith, P. M. Ueland, E. Nexo, R. Clarke, J. McPartlin, C. Johnston, F. Engbaek, J. Schneede, C. McPartlin, et al. Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion Clin. Chem., January 1, 2004; 50(1): 3 - 32. [Abstract] [Full Text] [PDF]
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R. Obeid, H. Schorr, R. Eckert, and W. Herrmann Vitamin B12 Status in the Elderly as Judged by Available Biochemical Markers Clin. Chem., January 1, 2004; 50(1): 238 - 241. [Full Text] [PDF]
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Z. Lloyd-Wright, A.-M. Hvas, J. Moller, T. A.B. Sanders, and E. Nexo Holotranscobalamin as an Indicator of Dietary Vitamin B12 Deficiency Clin. Chem., December 1, 2003; 49(12): 2076 - 2078. [Full Text] [PDF]
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M. Vakur Bor, S. N. Fedosov, N. B. Laursen, and E. Nexo Recombinant Human Intrinsic Factor Expressed in Plants Is Suitable for Use in Measurement of Vitamin B12 Clin. Chem., December 1, 2003; 49(12): 2081 - 2083. [Full Text] [PDF]
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A. McCaddon, P. Hudson, C. McCracken, R. Ellis, and A. McCaddon Biological Variation of Holo-Transcobalamin in Elderly Individuals Clin. Chem., September 1, 2003; 49(9): 1542 - 1544. [Full Text] [PDF]
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W. Herrmann, H. Schorr, R. Obeid, and J. Geisel Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians Am. J. Clinical Nutrition, July 1, 2003; 78(1): 131 - 136. [Abstract] [Full Text] [PDF]
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 H Refsum and A D Smith Low vitamin B-12 status in confirmed Alzheimer's disease as revealed by serum holotranscobalamin J. Neurol. Neurosurg. Psychiatry, July 1, 2003; 74(7): 959 - 961. [Abstract] [Full Text] [PDF]
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S. Loikas, M. Lopponen, P. Suominen, J. Moller, K. Irjala, R. Isoaho, S.-L. Kivela, P. Koskinen, and T.-T. Pelliniemi RIA for Serum Holo-Transcobalamin: Method Evaluation in the Clinical Laboratory and Reference Interval Clin. Chem., March 1, 2003; 49(3): 455 - 462. [Abstract] [Full Text] [PDF]
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 R. Carmel, R. Green, D. S. Rosenblatt, and D. Watkins Update on Cobalamin, Folate, and Homocysteine Hematology, January 1, 2003; 2003(1): 62 - 81. [Abstract] [Full Text] [PDF]
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R. Obeid, M. Jouma, and W. Herrmann Cobalamin Status (Holo-Transcobalamin, Methylmalonic Acid) and Folate as Determinants of Homocysteine Concentration Clin. Chem., November 1, 2002; 48(11): 2064 - 2065. [Full Text] [PDF]
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E. Nexo, A.-M. Hvas, O. Bleie, H. Refsum, S. N. Fedosov, S. E. Vollset, J. Schneede, J. E. Nordrehaug, P. M. Ueland, and O. K. Nygard Holo-Transcobalamin Is an Early Marker of Changes in Cobalamin Homeostasis. A Randomized Placebo-controlled Study Clin. Chem., October 1, 2002; 48(10): 1768 - 1771. [Abstract] [Full Text] [PDF]
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R. Carmel Measuring and Interpreting Holo-Transcobalamin (Holo-Transcobalamin II) Clin. Chem., March 1, 2002; 48(3): 407 - 409. [Full Text] [PDF]
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