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Determining vitamin D status: a comparison between commercially available assays.

Snellman G, Melhus H, Gedeborg R, Byberg L, Berglund L, Wernroth L, Michaëlsson K - PLoS ONE (2010)

Bottom Line: High inter-assay disagreement was found.The strongest correlation was found for HPLC-APCI-MS (r = 0.7), intermediate for RIA (r = 0.5) and lowest for CLIA (r = 0.4).The most valid method was HPLC-APCI-MS.

View Article: PubMed Central - PubMed

Affiliation: Section of Orthopaedics, Department of Surgical Sciences, Uppsala University, [corrected] Uppsala, Sweden. greta.snellman@surgsci.uu.se

ABSTRACT

Background: Vitamin D is not only important for bone health but can also affect the development of several non-bone diseases. The definition of vitamin D insufficiency by serum levels of 25-hydroxyvitamin D depends on the clinical outcome but might also be a consequence of analytical methods used for the definition. Although numerous 25-hydroxyvitamin D assays are available, their comparability is uncertain. We therefore aim to investigate the precision, accuracy and clinical consequences of differences in performance between three common commercially available assays.

Methodology/principal findings: Serum 25-hydroxyvitamin D levels from 204 twins from the Swedish Twin Registry were determined with high-pressure liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS), a radioimmunoassay (RIA) and a chemiluminescent immunoassay (CLIA). High inter-assay disagreement was found. Mean 25-hydroxyvitamin D levels were highest for the HPLC-APCI-MS technique (85 nmol/L, 95% CI 81-89), intermediate for RIA (70 nmol/L, 95% CI 66-74) and lowest with CLIA (60 nmol/L, 95% CI 56-64). Using a 50-nmol/L cut-off, 8% of the subjects were insufficient using HPLC-APCI-MS, 22% with RIA and 43% by CLIA. Because of the heritable component of 25-hydroxyvitamin D status, the accuracy of each method could indirectly be assessed by comparison of within-twin pair correlations. The strongest correlation was found for HPLC-APCI-MS (r = 0.7), intermediate for RIA (r = 0.5) and lowest for CLIA (r = 0.4). Regression analyses between the methods revealed a non-uniform variance (p<0.0001) depending on level of 25-hydroxyvitamin D.

Conclusions/significance: There are substantial inter-assay differences in performance. The most valid method was HPLC-APCI-MS. Calibration between 25-hydroxyvitamin D assays is intricate.

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Related in: MedlinePlus

Seasonal differences in 25-hydroxyvitamin D levels for the HPLC-APCI-MS, RIA and CLIA assays.The error bars indicate 95% confidence intervals.
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pone-0011555-g002: Seasonal differences in 25-hydroxyvitamin D levels for the HPLC-APCI-MS, RIA and CLIA assays.The error bars indicate 95% confidence intervals.

Mentions: Our results reveal low inter-assay agreement. Mean 25-hydroxyvitamin D values and basic characteristics of the twins are presented in Table 1. HPLC-APCI-MS measured a mean 25-hydroxyvitamin D level of 85 nmol/L, RIA 70 nmol/L and CLIA 60 nmol/L, p for difference between assays <0.0001 (Figure 1). 25-hydroxyvitamin D2 was detectable in only 20% (n = 40) of our subjects using the HPLC-APCI-MS assay. The mean level among these 40 twins was 8 nmol/L, and they contributed to only 1.5 nmol/L of the mean 25-hydroxyvitamin D level among all 204 twins. Demonstrated in Figure 2, the serum 25-hydroxyvitamin D levels were significantly higher with all methods during the summer compared to the winter season. The greatest inter-seasonal difference, 23 nmol/L (95% CI 13–33), is presented by the HPLC-APCI-MS assay.


Determining vitamin D status: a comparison between commercially available assays.

Snellman G, Melhus H, Gedeborg R, Byberg L, Berglund L, Wernroth L, Michaëlsson K - PLoS ONE (2010)

Seasonal differences in 25-hydroxyvitamin D levels for the HPLC-APCI-MS, RIA and CLIA assays.The error bars indicate 95% confidence intervals.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2903481&req=5

pone-0011555-g002: Seasonal differences in 25-hydroxyvitamin D levels for the HPLC-APCI-MS, RIA and CLIA assays.The error bars indicate 95% confidence intervals.
Mentions: Our results reveal low inter-assay agreement. Mean 25-hydroxyvitamin D values and basic characteristics of the twins are presented in Table 1. HPLC-APCI-MS measured a mean 25-hydroxyvitamin D level of 85 nmol/L, RIA 70 nmol/L and CLIA 60 nmol/L, p for difference between assays <0.0001 (Figure 1). 25-hydroxyvitamin D2 was detectable in only 20% (n = 40) of our subjects using the HPLC-APCI-MS assay. The mean level among these 40 twins was 8 nmol/L, and they contributed to only 1.5 nmol/L of the mean 25-hydroxyvitamin D level among all 204 twins. Demonstrated in Figure 2, the serum 25-hydroxyvitamin D levels were significantly higher with all methods during the summer compared to the winter season. The greatest inter-seasonal difference, 23 nmol/L (95% CI 13–33), is presented by the HPLC-APCI-MS assay.

Bottom Line: High inter-assay disagreement was found.The strongest correlation was found for HPLC-APCI-MS (r = 0.7), intermediate for RIA (r = 0.5) and lowest for CLIA (r = 0.4).The most valid method was HPLC-APCI-MS.

View Article: PubMed Central - PubMed

Affiliation: Section of Orthopaedics, Department of Surgical Sciences, Uppsala University, [corrected] Uppsala, Sweden. greta.snellman@surgsci.uu.se

ABSTRACT

Background: Vitamin D is not only important for bone health but can also affect the development of several non-bone diseases. The definition of vitamin D insufficiency by serum levels of 25-hydroxyvitamin D depends on the clinical outcome but might also be a consequence of analytical methods used for the definition. Although numerous 25-hydroxyvitamin D assays are available, their comparability is uncertain. We therefore aim to investigate the precision, accuracy and clinical consequences of differences in performance between three common commercially available assays.

Methodology/principal findings: Serum 25-hydroxyvitamin D levels from 204 twins from the Swedish Twin Registry were determined with high-pressure liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS), a radioimmunoassay (RIA) and a chemiluminescent immunoassay (CLIA). High inter-assay disagreement was found. Mean 25-hydroxyvitamin D levels were highest for the HPLC-APCI-MS technique (85 nmol/L, 95% CI 81-89), intermediate for RIA (70 nmol/L, 95% CI 66-74) and lowest with CLIA (60 nmol/L, 95% CI 56-64). Using a 50-nmol/L cut-off, 8% of the subjects were insufficient using HPLC-APCI-MS, 22% with RIA and 43% by CLIA. Because of the heritable component of 25-hydroxyvitamin D status, the accuracy of each method could indirectly be assessed by comparison of within-twin pair correlations. The strongest correlation was found for HPLC-APCI-MS (r = 0.7), intermediate for RIA (r = 0.5) and lowest for CLIA (r = 0.4). Regression analyses between the methods revealed a non-uniform variance (p<0.0001) depending on level of 25-hydroxyvitamin D.

Conclusions/significance: There are substantial inter-assay differences in performance. The most valid method was HPLC-APCI-MS. Calibration between 25-hydroxyvitamin D assays is intricate.

Show MeSH
Related in: MedlinePlus