J. M. van den Ouweland, A. Beijers, H. van Daal
Oct 9, 2013
Citations
0
Influential Citations
24
Citations
Quality indicators
Journal
Clinical Chemistry and Laboratory Medicine (CCLM)
Abstract
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.