Endocrine Abstracts

Background: Vitamin D is an important contributor to musculoskeletal health and its potential involvement has recently been underlined in several non-skeletal diseases. Measurement of circulating levels of 25-hydroxyvitamin D (25OHD) represents the most reliable assessment of vitamin D status. Several assays are available but are not commutable because of a lack of of standardization. The aim of our study was to evaluate the performance of a new ELISA for measurement of 25OHD levels.

Methods: 25OHD levels were measured with a newly released ELISA (Diasource Immunoassays), a simplified method without pre-treatment step. Method comparison was performed using 199 patients’ samples with automated chemiluminescent immunoassay commonly used in clinical laboratories (Liaison, DiaSorin).

Results: According to our automated assay routine cut-points, serum concentrations of 25OHD were below 20 ng/ml in 96 patients, between 20 and 30 ng/ml in 68 patients and above 30 ng/ml in 35. The ELISA and the automated methods were significantly correlated (r=0.9230; P<0.0001) and the Passing and Bablock regression analysis showed a slope of 1.218 (95% CI: 1.1434 to 1.2944) and an intercept of −1.8775 ng/ml (95% CI −3.2694 to −0.3363). A small negative difference (2.7905 ng/ml; 95% CI −3.4546 to −2.1265) was highlighted, for the ELISA method through the Bland and Altman plot and important discrepancies (higher than 10 ng/ml) were observed in 12 samples.

Conclusions: Our preliminary results showed that the new 25OHD ELISA assay demonstrated a good agreement with a commonly used assay. A small difference was evidenced but its clinical impact is limited. However, additional investigations will be required to confirm the performances of this new simplified ELISA assay.