Specifications for trueness and precision of a reference measurement system for serum/plasma 25-hydroxyvitamin D analysis
The divergence in analytical quality of serum/plasma 25-hydroxy-vitamin D analysis calls for defining specifications for a reference measurement system. Fundamentally, in a reference measurement system, there should be a relationship between the analytical specifications for higher- (reference) and lower-order (routine) measurements. Therefore, when setting specifications, we started with limits for routine imprecision (CV(rou)) and bias (B(rou)) using 4 models: (1) the misclassifications in diagnosis, (2) biological variation data (reference interval (RI) and monitoring), (3) expert recommendations, and (4) state-of-the-art performance. Then, we used the derived goals to tailor those for reference measurements and certified reference materials (CRMs) for calibration by setting the limits for CV(ref) at 0.5 CV(rou), B(ref) at 0.33 B(rou)(,) max. uncertainty (U(max)) at 0.33 B(ref). The established specifications ranged between CV(rou)<or=22%, B(rou)<or=10%, CV(ref)<or=11%, B(ref)<or=3.3%, U(max) 1.1% (model 3) and CV(rou)<or=4%, B(rou)<or=2.6%, CV(ref)<or=2%, B(ref)<or=0.9%, U(max) 0.3% (model 2, monitoring). Model 2 (monitoring) gave the most stringent goals, model 3, the most liberal ones. Accounting for state-of-the-art performance and certification capabilities, we used model 2 (RI) to recommend achievable goals: for routine testing, CV(rou)<or=10%, B(rou)<or=5%, for reference measurements, CV(ref)<or=5%, B(ref)<or=1.7%, and for CRMs, U(max) 0.6%.
[Show abstract] [Hide abstract] ABSTRACT: Measurement of vitamin D has increased significantly over the last years due to its involvement not only in calcium homeostasis, but also in the pathogenesis of various autoimmune- and infectious diseases. In the majority of studies, emphasis has been on 25-hydroxyvitamin D, which is regarded the best indicator of vitamin D status, whereas recently more interest has arisen in a combined measurement of multiple clinically relevant vitamin D metabolites. LC-MS/MS is a powerful technique allowing simultaneous determination of various vitamin D metabolites covering a broad dynamic range. Multi-panel LC-MS/MS assays are likely to enhance future investigations regarding the optimal combination of metabolites for the assessment of vitamin D sufficiency as well as help us in gaining better understanding of vitamin metabolism in health and disease. This article reviews recent advances in the quantification of the major vitamin D metabolites by LC-MS/MS and their application in clinical research.0Comments 0Citations
- "To meet the growing demands for RMP services due to worldwide efforts in standardization of 25(OH)D measurement , the Centers of Disease Control and Prevention (CDC) has developed a candidate RMP for serum 25(OH)D3 and 25(OH)D2 measurements using LC-MS/MS . Their method meets predefined specifications (≤5% coefficient of variation (CV) and ≤1.7% bias) for a RMP for 25(OH)D metabolites  . NIST provides standard reference material SRM 972a, which consists of four vials (Levels 1 through 4) of human native serum with specific target levels of 25(OH)D3, 25(OH)D2 and 3-epi-25(OH)D3 (level 4 contains "
[Show abstract] [Hide abstract] ABSTRACT: Background: We evaluated the analytical and clinical performance of the new Lumipulse® G 25-OH vitamin D assay from Fujirebio, and compared it to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method and three other commercial automated assays. Methods: Total 25 hydroxy vitamin D (25(OH)D) levels were measured in 100 selected serum samples from our routine analysis with Fujirebio 25(OH)D assay. The results were compared with those obtained with LC-MS/MS and three other automated 25(OH)D assays (Abbott, Beckman, and Roche). The accuracy of each assay tested was evaluated against a Labquality reference serum panel for 25(OH)D (Ref!25OHD; University of Ghent). Results: Intra- and inter-day imprecision of the Fujirebio 25(OH)D assay was <5%. Fujirebio 25(OH)D assay showed the highest correlation among the assays tested with the LC-MS/MS method (R=0.986). The mean relative bias obtained was -15.6% (Fujirebio), -12.7% (Beckman), -2.1% (Abbott) and 9.7% (Roche) as compared to LC-MS/MS. Comparison with the Labquality certified reference serum panel yielded a mean bias of -11.8% (Fujirebio), -14.1% (Beckman), 4.4% (Abbott) and 3.2% (Roche), respectively. Compared to LC-MS/MS, the sensitivity of different methods in detecting vitamin D insufficiency (<50 nmol/L) varied from 100% for the Fujirebio assay to 72.7% for Roche, and specificity ranged from 94.4% for Roche to 87.6% for Beckman. Conclusions: The Lumipulse G 25-OH vitamin D assay from Fujirebio demonstrated a good correlation with LC-MS/MS and some immunoassays. The performance of the assay is well-suited for routine 25(OH)D measurement in clinical serum samples. A correction for the observed negative bias vs. LC-MS/MS could be considered.0Comments 1Citation
- "SD); –12.5 to 11.6)] as shown inFigure 1B. The estimated bias was clearly under the limit of bias ( ≤ 5%) as recommended by Stöckl et al.  and the Vitamin D Standardization Program (VDSP). Five of the reference serum samples contained significant concentrations of 25(OH)D2 ranging from 5.1 nmol/L to 55.4 nmol/L corresponding to 9.6% to 48.8% of the total 25(OH)D. "
[Show abstract] [Hide abstract] ABSTRACT: The study was conducted to evaluate the analytical and clinical performance of the VIDAS® 25-OH Vitamin D Total assay. The clinical performance of the assay was compared with four other immunoassays against the results of two different liquid chromatography/mass spectrometry methods (LC-MS/MS) standardized to NIST reference materials. VIDAS® 25-OH Vitamin D Total assay precision, linearity, detection limits and sample matrix comparison were assessed following CLSI guidelines. For method comparison, a total of 150 serum samples ranging from 7 to 92 ng/mL were analyzed by all the methods. Correlation was studied using Passing-Bablok regression and Bland-Altman analysis. The concordance correlation coefficient (CCC) was calculated to evaluate agreement between immunoassays and the reference LC-MS/MS method. In addition, samples containing endogenous 25(OH)D2 were used to assess each immunoassay's ability to detect this analyte. Pregnancy and hemodialysis samples were used to the study the effect of vitamin D binding protein (DBP) concentration over VIDAS® assay performance. The VIDAS® 25-OH Vitamin D Total assay showed excellent correlation to the LC-MS/MS results (y=1.01x+0.22 ng/mL, r=0.93), as obtained from two different sites and distinct LC-MS/MS methods. The limit of quantification was determined at 8.1 ng/mL. Cross-reactivity for 25(OH)D2 was over 80%. At concentrations of 10.5, 26 and 65.1 ng/mL, within-run CVs were 7.9%, 3.6% and 1.7%, while total CVs (between runs, calibrations, lots and instruments) were 16.0%, 4.5% and 2.8%. The VIDAS® performance was not influenced by altered DBP levels, though under-recovery of 25(OH)D as compared to LC-MS/MS was observed for hemodialysis samples. The VIDAS® 25-OH Vitamin D Total assay is therefore considered suitable for assessment of vitamin D status in clinical routine.0Comments 1Citation
- "For vitamin D, within-subject variation has been shown to reach 12% . Stockl et al.  proposed an acceptable CV of < 10% for routine measurement purposes, emphasizing that the precision bias should be set at half this limit to routinely achieve the required quality. Therefore, using a target value of CV = 5%, the VIDAS ® 25-OH Vitamin D Total assay meets this requirement for within-run precision ( repeatability) at thresholds of 20 ng/mL, 30 ng/mL and 100 ng/mL (Table 1). "