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Endocrine Abstracts (2015) 37 EP249 | DOI: 10.1530/endoabs.37.EP249

ECE2015 Eposter Presentations Calcium and Vitamin D metabolism (96 abstracts)

Analytical evaluation of a new fully automated immunoassay for the quantification of 1,25-dihydroxyvitamin D

Nathalie Miller & Damien Gruson


Cliniques Universitaires St Luc, Brussels, Belgium.


Background: Quantification of 1,25-dihydroxyvitamin D (1,25(OH)2D) remains challenging because of low circulating concentrations and potent cross-reactivities with steroid-like structures. The most frequent assays for 1,25(OH)2D testing are still based on RIA format with preliminary extraction. The analytical performances and the turnaround time of analysis (TAT) for these assays are limited. Several novel assays for 1,25(OH)2D testing are emerging. The aim of our study was therefore to evaluate the analytical performances of a recently developed automated immunoassay for the measurement of 1,25(OH)2D.

Methods: We evaluated the performances of the LIAISON XL 1,25(OH)2D assay (DiaSorin), a fully automated immunoassay that uses a recombinant fusion protein for capturing 1,25(OH)2D. The limit of detection and the within- and between-run imprecision were determined. Method comparison was performed with our routine RIA method and with a reference Liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

Results: The limit of detection was <5 pg/ml. The within-run coefficients of variation (CV) were 2.6 and 4.4% for 1,25(OH)2D concentrations of 6.7 and 19.7 pg/ml and the between run CVs were 9.3 and 13.1% for concentrations of 25.4 and 101.1 pg/ml. The automated 1,25(OH)2D assay was significantly correlated to RIA (r=0.74; P<0.0001) and LC-MS/MS (r=0.9975; P<0.0001). The comparison of the automated assay and RIA revealed through Passing-Bablok regression analysis a slope of 0.86 and an intercept of 14.12. The mean bias observed on the Bland-Altman plot was −2.8 pg/ml. The comparison of automated assay and LC-MS/MS revealed through Passing-Bablok regression analysis a slope of 1.07 and an intercept of −1.87. The mean bias observed on the Bland-Altman plot was −8.2 pg/ml.

Conclusion: The LIAISON XL 1,25(OH)2D automated assay demonstrated superior analytical performances in comparison to RIA assay and a clear improvement of TAT. Furthermore, we demonstrated a strong agreement between this 1,25(OH)2D automated assay and a reference LC-MS/MS method.

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