We are pleased that our paper has generated the discussion in the Journal, further highlighting the issues with measurement of vitamin D status. In light of recent publications of high prevalence of vitamin D deficiency in Australia, it is important that clinicians are aware of the scope of the problems in measurement of vitamin D status.All of the laboratories measuring 25(OH)D for this study1 participated in DEQAS, the external quality assurance programmes for the measurement of 25(OH)D at the time of the study measurements. The Diasorin Liaison measurements were completed in November 2007 and the liquid chromatographydual mass spectrometry (LC-MS/MS) in October 2008. The National Institute of Standards and Technology (NIST) standard 972 for measurement of 25(OH)D was released on 8 July 2009. Thus, at the time that the samples were tested, none of the labs was calibrating against the NIST standard.
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