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Clinical Trial
. 2015 Jun 5;25(2):203-12.
doi: 10.11613/BM.2015.020. eCollection 2015.

Method evaluation study of a new generation of vitamin D assays

Dietmar Enko  1 , Gernot Kriegshäuser  1 , Robert Stolba  1 , Elfriede Worf  1 , Gabriele Halwachs-Baumann  1
Affiliations
Clinical Trial

Method evaluation study of a new generation of vitamin D assays

Dietmar Enko et al. Biochem Med (Zagreb). .

Abstract

Introduction: Recently several diagnostic manufacturers have launched new 25-hydroxy-vitamin D (25[OH]D) assays, which are aligned to the National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM) (NIST, Gaithersburg, Maryland). The aim of this study was to compare the performance of one liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, one enzyme linked immunosorbent assay (ELISA), and one recalibrated and previous version of a chemiluminescence immunoassay (CLIA).

Material and methods: Serum-aliquots of 198 patient samples from routine 25(OH)D analysis were measured by the ClinMass® LC-MS/MS Complete Kit (RECIPE Chemicals+Instruments GmbH, Munich, Germany), the ORGENTEC 25(OH)D3/D2 ELISA (ORGENTEC Diagnostika GmbH, Mainz, Germany), the recalibrated Immunodiagnostic Systems (IDS)-iSYS 25(OH)DS and the previous used IDS-iSYS 25(OH)D CLIA (Immunodiagnostic Systems Ltd, Boldon, United Kingdom). Bland-Altman and Deming regression analyses were calculated for methods comparison of all tested 25(OH)D assays. The LC-MS/MS method was defined as the reference method. Within-run and between-run precision measurements were performed for all methods with three different concentration levels.

Results: Compared to the LC-MS/MS method, the new IDS-iSYS 25(OH)DS and ORGENTEC 25(OH)D3/D2 assay demonstrated mean relative biases of 16.3% and 17.8%. The IDS-iSYS 25(OH)D assay showed the lowest mean bias of 1.5%. Deming regression analyses of the recalibrated IDS-iSYS 25(OH)DS and the ORGENTEC 25(OH)D3/D2 assay showed proportional differences, when compared to the reference method. All assays showed a within-run and between-run imprecision of ≤20% at each of the evaluated concentration levels.

Conclusions: The evaluated standardized immunoassays and LC-MS/MS are useful methods for measuring 25(OH)D serum-levels in clinical laboratories.

Keywords: immunoassays; liquid chromatography-tandem mass spectrometry; quality improvement; reference standards; vitamin D.

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Conflict of interest statement

Research funding cost for reagents were reimbursed by Immunodiagnostic Systems Ltd (Boldon, United Kingdom), ORGENTEC Diagnostika GmbH (Mainz, Germany), and RECIPE Chemicals + Instruments GmbH (Munich, Germany).

Figures

Figure 1
Figure 1
A-C: Bland-Altman plots of 25(OH)D assay comparisons. The mean relative bias in percent for all immunoassays compared to the LC-MS/MS (reference method) is represented in plain line. The limits of agreement are illustrated by dashed lines. ng/mL x 2.5 = nmol/L.
Figure 2
Figure 2
A-C: Deming regression plots of 25(OH)D assay comparisons. Bold lines represent Deming regression lines. The regression equation with the included 95% confidence intervals for the slope and intercept is presented next to the regression lines. CI - confidence interval. ng/mL x 2.5 = nmol/L.
Figure 3
Figure 3
Box-and-whisker plot of 25(OH)D assay comparisons. The central boxes represent the 25th to 75th percentile range. The lines inside the boxes show the median value for each method. The straight line shows the median value as measured by the liquid chromatography-tandem mass spectrometry (reference method). Recalibrated chemiluminescence immunoassay - IDS-iSYS 25(OH)DS assay, IQR - interquartile range. ng/mL x 2.5 = nmol/L.
See this image and copyright information in PMC

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