What is the therapeutic target level of 25-hydroxyvitamin D in osteoporosis and how accurately can we measure it?

摘要

In a previous issue of the Journal, Lai et al. described problems with inter-assay disagreement of 25-hydroxyvitamin D (25OHD) methods and subsequent correspondence by Lu and Sikaris and Ward et al. clarified some of the limitations of that study. With increasing requests for 25OHD analyses, many laboratories have transitioned from the use of labour-intensive, manual radioimmunoassay methods to automated immunoassay methods available on random-access analysers. In the process of combining extraction of 25OHD from its binding protein (vitamin D binding protein - DBP) to accurate and precise measurement of the displaced ligand, there has been concern that newer automated one-step methods may not be sufficiently sensitive and accurate for diagnostic purposes. The correspondence of Lu and Sikaris and Ward et al. quite rightly state that the use of isotope dilution liquid chromatography tandem mass spectrometry (LC-MSMS) as a reference method has its own inherent problems.