Surveillance evaluation of the standardization of assay values for serum total 25-hydroxyvitamin D concentration in Japan

摘要

To assess the vitamin D nutritional status, serum total 25-hydroxyvitamin D (25(OH)D) concentration is measured. We used six automated 25(OH)D immunoassays (AlAs) available in Japan and certified by the Vitamin D Standardization Program (VDSP) at the U.S. Center for Disease Control and Prevention to assess the concordance of the assay results.Methods: Serum total 25(OH)D concentrations in SRM 972a and 20 serum samples from patients were determined using three liquid chromatography-tandem mass spectrometry (LC-MS/MS) and six AlAs (pilot study), and an additional I 10 serum samples were assessed by the six AlAs (surveillance study). The assay bias from the results of LC-MS/MS by Chiba University or consensus values (i.e. average of six AlAs) was estimated using the procedure described in CLSI document EP09-A3.Results: LC-MS/MS at Chiba University could completely separate 25(OH)D2, 25(OH)D3 and 3-epi-25(OH)D3, and the observed values including total 25(OH)D in SRM 972a were all within ±ISD of the assigned values. All AlAs produced results greater than ±3SD. In the pilot study, four of the six AlAs had an average percentage bias, as estimated by confidence interval (Cl), larger than ±5% (acceptance criterion in CLSI); the bias converged from —6.5% to 3.2% after adjustment by LC-MS/MS. In the surveillance study, 25(OH)D concentrations in AlAs all adjusted to LC-MS/MS converged within ±5% from consensus values. However, some AlAs showed negative or positive bias from the consensus values.Conclusions: Current AlAs in Japan continue to lack standardization. Manufacturers should implement quality assurance strategies so that their values more closely align to those of standard reference material 972a.