Abstract
Determination of plasma vitamin B12 (B12) is a frequently requested laboratory analysis, mainly employed to establish B12 deficiency. However, an increased level of B12 is a common unexpected finding that may be related to an increased concentration of one of the B12 binding proteins, haptocorrin or transcobalamin. This paper describes the extensive laboratory evaluation of a patient with an elevated level of plasma B12 with various well-established assays. Initial studies suggested the presence of a macromolecule consisting of haptocorrin bound B12. Specific determinations of the B12-binding proteins revealed normal amounts of haptocorrin but a markedly increase in both total and B12 saturated transcobalamin (holo-TC). The results are in accord with the presence of macro-transcobalamin. These experiments reveal that determination of the nature of the B12-macromolecules is troublesome due to differences in assays applied to measure these proteins. In addition, this publication creates awareness of macro-holo-TC as a cause of an unexplained increased B12 level.
Original language | English |
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Article number | 00045632221087132 |
Pages (from-to) | 302-307 |
Number of pages | 6 |
Journal | Annals of Clinical Biochemistry |
Volume | 59 |
Issue number | 4 |
Early online date | 25 Apr 2022 |
DOIs | |
Publication status | Published - Jul 2022 |
Keywords
- Vitamin B12
- B12
- haptocorrin
- transcobalamin
- macromolecule
- HOLO-TRANSCOBALAMIN
- DEFICIENCY
- ANTIBODY
- PATIENT
- IGG
- MARKER