Harmonization of serum 25‐hydroxycalciferol assay results from high‐performance liquid chromatography, enzyme immunoassay, radioimmunoassay, and immunochemiluminescence systems: A multicenter study

Abstract

Our findings showed that with adjustment of circulating 25(OH)D based on HPLC, frequency distribution of vitamin D status, as judged by different methods, can be well harmonized with no statistically significant inter-system difference.

What is the definition of "vitamin D deficiency" and who is considered "vitamin D deficient"? Urgent need for a national consensus

“…Based on our experience, we believe that circulating 25(OH)D concentrations of 50 nmol/L (20 ng/mL) and above based on HPLC assay system could be considered adequate. This cutoff point could vary according to the assay system (42). Nevertheless, a national consensus is urgently needed on definition of adequate vitamin D status.…”

“…The other important issue is the variability of calcidiol assay results from different assay systems. To overcome this problem, employment of assayspecific cutoff points (40) as well as harmonization and standardization of the assay results have been proposed (41)(42). Based on our experience, we believe that circulating 25(OH)D concentrations of 50 nmol/L (20 ng/mL) and above based on HPLC assay system could be considered adequate.…”

Randomized controlled trials of vitamin D and cancer incidence: A modeling study

“…While the modeling suggested should contribute to designing, and analyzing, vitamin D RCT data for many health outcomes, this approach depends on reliable, accurate, reproducible and comparable 25(OH)D assays, with harmonization of findings where different assay systems are used, all of which are now achievable [ 39 ],[ 40 ],[ 41 ].…”

Healthy changes in some cardiometabolic risk factors accompany the higher summertime serum 25-hydroxyvitamin D concentrations in Iranian children: National Food and Nutrition Surveillance

“…The strengths of the present study include the large sample size and coverage of a rather broad latitudinal range, with fairly good distribution across the country. Serum 25(OH)D assay results were checked using the HPLC method as an attempt to harmonize the results ( 65 ) . However, some limitations must be acknowledged.…”