UK Food Standards Agency Workshop Consensus Report: the choice of method for measuring 25-hydroxyvitamin D to estimate vitamin D status for the UK National Diet and Nutrition Survey.

The consensus workshop, organised on behalf of the Food Standards Agency, was convened to recommend the most appropriate and secure method for measuring vitamin D status in the UK. Workshop participants (the Expert Panel) were invited on the basis of expertise in current 25-hydroxyvitamin D (25OHD) assays, or expertise in vitamin D nutrition and metabolism or detailed knowledge and experience in the National Diet and Nutrition Survey (NDNS). A decision support matrix, which set out the particular criteria by which the different options were scored and evaluated, was used to structure the discussion. The Expert Panel agreed that five methods for measuring 25OHD should be evaluated according to eleven criteria, selected on the basis of their relevance to the NDNS. All three of the evaluating subgroups of the Expert Panel produced similar total scores over the eleven criteria for the different methods; they scored LC-MS/MS and HPLC-UV similarly highly, while the scores for the immunoassay methods were lower. The Expert Panel recommended that an LC-MS/MS method should be the preferred method for the NDNS. A detailed specification for the method will be required to ensure comparability between NDNS and the National Health and Nutrition Examination Survey in the US facilitating future comparisons. The Expert Panel also recommended that the method should be carried out in a laboratory with appropriate expertise, competency and history of records of good performance. The method should be standardised against the National Institute of Standards and Technology SRM 972. If the recommended LC-MS/MS is adopted, the Expert Panel indicated that the method should be able to discriminate the C-3 epimer of 25OHD(3), especially if used to measure 25OHD in young infants in the forthcoming Diet and Nutrition Survey of Infants and Young Children, who are known to have high circulating concentrations of the C-3 epimer.