Comparison of two 25-hydroxyvitamin D immunoassays to liquid chromatography-tandem mass spectrometry in assessing samples from the Chinese population.

Background: We compared the utility of two 25-OH-D immunoassays to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for assessing human serum samples from the Chinese population.

Methods: In total, 451 Chinese serum samples were tested using the IDS 25-Hydroxy Vitamin D EIA kits and the LC-MS/MS 25-OH-D method. Of these, 239 samples were also analysed using DiaSorin 25-Hydroxyvitamin D RIA kits.

Results: The regression coefficients (r) between LC-MS/MS and immunoassays were 0.8430 (95% CI: 0.8140-0.8678) for IDS-EIA and 0.8187 (95% CI: 0.7720-0.8566) for DiaSorin-RIA. Using the Passing-Bablok analysis, IDS-EIA and DiaSorin-RIA yielded results equivalent to those from LC-MS/MS. However, IDS-EIA showed negative bias and DiaSorin-RIA showed positive bias when compared to LC-MS/MS, as indicated by the Bland-Altman plots. By the kappa test, both IDS-EIA and DiaSorin-RIA were in acceptable agreement with LC-MS/MS in the assessment of vitamin D deficiency and insufficiency.

Conclusions: Although some systematic bias was found, the DiaSorin-RIA and IDS-EIA kits met the minimum performance goal for 25-OH-D measurement and can be recommended for routine use in the Chinese population. However, further studies are needed to assess 25-OH-D measurement immunoassays with lower bias and that are more suitable for the Chinese population.