Use of a common standard improves the performance of liquid chromatography-tandem mass spectrometry methods for serum 25-hydroxyvitamin-D

Abstract

Use of a common standard improved agreement among laboratories using LC-MS/MS methods for 25-OH-D. This suggests that problems with assay standardization contribute to interlaboratory imprecision. This may be related to the nature of the matrix used for working standards or errors in the calibration of stock standard solutions of 25-OH-D. Some participants used a gravimetric method, others UV spectrophotometry, to establish the concentration of stock solutions. Among the latter group there was uncertainty over the molar absorption coefficient of 25-OH-D solutions. We conclude that LC-MS/MS is not yet sufficiently robust to become the reference method for 25-OH-D and that gas chromatography-mass spectrometry might be a more suitable candidate.