Interlaboratory comparison of 25-hydroxyvitamin D determination
Clinical Chemistry
|July 1, 1984
Summary
Interlaboratory studies revealed significant variability in serum 25-hydroxyvitamin D (25-OH-D) measurements. Chromatography before assay is recommended for accurate vitamin D testing, improving reliability.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Nutritional Science
Background:
- Accurate measurement of serum 25-hydroxyvitamin D (25-OH-D) is crucial for assessing vitamin D status.
- Existing assays exhibit considerable interlaboratory variation, impacting clinical interpretation.
Purpose of the Study:
- To evaluate the performance of different methods for quantifying 25-OH-D in serum across multiple laboratories.
- To identify factors contributing to variability and recommend optimal assay methodologies.
Main Methods:
- An interlaboratory study involving 15 European laboratories.
- Comparison of various analytical methods, including chromatographic and non-chromatographic assays.
- Assessment of reproducibility and accuracy of 25-OH-D measurements.
Main Results:
- Laboratories could distinguish normal from high 25-OH-D levels, but overlap occurred for low and normal concentrations in some.
- Significant interlaboratory variation was observed, with 24,25(OH)2D3 interfering in most assays.
- Liquid chromatography with UV detection demonstrated suitability as a reference method.
Conclusions:
- Chromatographic methods, particularly liquid chromatography, are favored over non-chromatographic assays for accurate 25-OH-D quantification.
- Competitive protein binding assay is suitable for routine determinations.
- Standardization efforts require control sera with defined 25-OH-D concentrations.
