Evaluation of a new non-competitive chemiluminescent immunoassay for 25-OH vitamin D measurement.

OBJECTIVES: The increasing demand for vitamin D measurement over the past few decades has prompted manufacturers to develop automated chemiluminescence immunoassay (CLIA), including the noncompetitive anti-immune complex assay (NACA) system for the measurement of small molecules. This study aims to evaluate the performance of the Snibe-NACA 25-OH Vitamin D assay for measuring total 25-Hydroxy Vitamin D assay [25(OH)D] levels. METHODS: A total of 200 serum samples were collected from a clinical laboratory for 25(OH)D assay to evaluate the performance of the Snibe-NACA 25-OH Vitamin D assay using a double-blind method. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used as a reference method and the results were compared with those obtained from four other chemiluminescence competitive 25(OH)D assays. RESULTS: The Snibe-NACA 25-OH Vitamin D assay demonstrated satisfactory analytical performance with optimal precision (repeatability CV: 1.13-2.75 %;intra-laboratory CV: 1.59-2.58 %) and relatively small bias (-3.84 % mean relative bias compared with the LC-MS/MS),excellent agreement with LC-MS/MS, as evidenced by Passing-Bablok regression (R2: 0.9245, slope: 0.99, 95 % CI: 0.96-1.03; intercept: -1.24, 95 % CI: -3.49 to 0.65) and high correlation (Spearman's ρ=0.969; ICC=0.9584). Notably, the assay showed the highest concordance with LC-MS/MS in the classification of vitamin D status, achieving an overall agreement of 87.0 %, with particularly strong concordance in identifying deficiency (97.8 %). CONCLUSIONS: The Snibe-NACA 25-OH Vitamin D assay demonstrated good performance and compared favorably with both LC-MS/MS and other competitive assays, providing evidence of its high reliability in clinical diagnostic practice.