Observations from the UK Supra-Regional Assay Service laboratory for the measurement of Vitamin D metabolites

As a Supra-Regional Assay Service (SAS) laboratory, we receive samples from all over the UK. Of these some are sent frozen and others by post or courier. We have examined transport and storage conditions to see whether they affect the measurement of Vitamin D metabolites and potentially contribute to the variation in measurement of 25-hydroxyvitamin D (25OHD) seen in the DEQAS scheme. We have also examined the samples received during 2005. We found that different transport and storage conditions did not contribute significantly to the normal variation seen in measuring Vitamin D metabolites (CV% (+/- S.E.) for stored versus assay controls: 5.1 +/- 0.06% versus 4.5 +/- 0.04% for 250HD and 10.8 +/- 1.0% versus 12.3 +/- 1.0% for 1,25D). A review of the service showed a 240% increase in samples received over the last 5 years. Despite an increased awareness of the need to measure Vitamin D status, in this cross-section of patient samples 92% of Asian and 86% of white patients were found to be Vitamin D-insufficient (< 30 ng/ml) and 27% of Asian and 14% of white patients were profoundly deficient (< 5 ng/ml) and at risk of bone disease. (c) 2006 Elsevier Ltd. All fights reserved.