Comparison of the Serum Total 25-Hydroxyvitamin D Concentrations Using Chemiluminescent Immunoassay and Liquid Chromatography-Tandem Mass Spectrometry in Children

We aimed to assess the difference and agreement between the CL-series Vitamin D Total assay (Mindray), which was a kind of chemiluminescent immunoassay (CLIA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the measurement of serum 25-hydroxyvitamin D [25(OH)D] concentrations in children. We compared the 25(OH)D concentrations of 92 children using the CLIA and LC-MS/MS. Paired samples t-test was used to compare the two groups. Linear regression was used to show the correlation between CLIA and LC-MS/MS. The difference and bias between 2 methods were revealed in Bland-Altman plot. Agreement in classification of deficiency between CLIA and LC-MS/MS was assessed using Cohen's Kappa. p value<0.05 was considered statistically significant. Using Shapiro-Wilk Test to assess whether the data follows a normal distribution. Using 95% children's serum 25(OH)D concentrations by LC-MS/MS as the reference interval. The regression equation was CLIA =1.185 x LC-MS/MS- 3.328. The fitness adjusted r 2 was 0.589. The CLIA showed positive bias compared to LC-MS/MS, p<0.05, bias= (1.94 +/- 16.56) ng/mL. Cohen's Kappa =0.53, p<0.001. The agreement of 2 methods in diagnosing "deficiency" was good. According to Shapiro-Wilk Test, the data followed a normal distribution (W=0.99). The reference interval of children's serum 25(OH)D concentrations by LC-MS/MS was 11.35-44.57 ng/mL. In measuring 25(OH)D concentration of children, CLIA represented higher levels than LC-MS/MS. The two methods were consistent in diagnosing vitamin D deficiency. The reference interval of children's serum 25(OH)D concentrations by LC-MS/MS was 11.35-44.57 ng/mL in our area in summer.