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Evaluation of 3-epi-25-hydroxyvitamin D3 Cross-Reactivity in the Roche Elecsys Vitamin D Total Protein Binding Assay

Johannes M W van den Ouweland, Antonius M Beijers, Henny van Daal, Marc G L M Elisen, Gerard Steen, Jos P M Wielders

Clin Chem Lab Med. 2014 Mar;52(3):373-80.

PMID: 24108209

Abstract:

Background:
Presence of the 3-epi-25-hydroxyvitamin D3 [3-epi-25(OH)D3] metabolite affects accurate determination of 25(OH)D3 by most routine liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods and to an unknown extent in present immuno- and protein binding assays. We studied 3-epi-25(OH)D3 cross-reactivity in a competitive protein binding (CPB) assay (Roche Elecsys).
Methods:
Neonatal samples, containing up to 58% of 3-epi-25(OH)D3 were used for measurement by the CPB assay and by an LC-MS/MS method separating 25(OH)D3 and 3-epi-25(OH)D3. Analytical recovery was also studied by addition of exogenous 3-epi-25(OH)D3.
Results:
The CPB assay showed approximately 51% cross-reactivity to 3-epi-25(OH)D3 at exogenous addition. In contrast, there was minimal 3-epi-25(OH)D3 recognition by the CPB assay when present as the natural endogenous metabolite.
Conclusions:
The automated CPB assay displays minimal 3-epi-25(OH)D3 cross-reactivity in samples containing significant concentrations of endogenous 3-epi-25(OH)D3. Exogenous 3-epi-25(OH)D3 added to human serum or plasma seems to behave different from endogenous presence, and caution is warranted when using samples spiked with vitamin D metabolites for testing analytical specificity or external quality assurance in immuno- or protein binding assays.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP73809059-A 3-epi-25-Hydroxyvitamin D3 3-epi-25-Hydroxyvitamin D3 73809-05-9 Price
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