Cobalamin

cob

What is measured?

Synonym: Vitamin B12.
Biologically active cobalamin and not cobalamin analogues (which do not bind to intrinsic factor).

Method(s): Microbiological assay, using colistin sulphate-resistant strain of Lactobacillus leichmannii (1). The assay has been adopted to a microtiter plate format and is carried out by a robotic workstation. Notably, samples containing antibiotic(s) that inhibit(s) the growth of Lactobacillus leichmannii may cause assay interference.

Indication(s)

Cobalamin deficiency or assessment of cobalamin status (2).

Specimen, collection and processing

Patient/subject: Some antibiotics may inhibit growth of of Lactobacillus leichmannii, and may cause artificial, low cobalamin levels.
Matrix: Serum or plasma.
Volume: Minimum volume is 100 µL, but 250 µL is optimal and allows reanalysis.
Preparation and stability: Cobalamin is light sensitive, but is stable for years in samples frozen at -20 °C or below.

Transportation

Frozen, on dry ice. (for general instruction on transportation, click here.)

Reported values

Reported values: > 150 pmol/L.
Intraclass correlation coefficient (ICC): 0.82.

Literature

1. Kelleher, B.P., and Broin, S.D. (1991). Microbiological assay for vitamin B12 performed in 96-well microtitre plates. J Clin Pathol 44, 592-95.
2. Green, R., Allen, L.H. Bjørke-Monsen, A-L., Brito, A., Gueant, J-L. Miller, J.W., Nexo, E., Stabler, S., Toh, B-H., Ueland, P.M. and Yajnik, C. (2017). Vitamin B12 deficiency. Nat Rev Dis Prim 3: 17040.

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