Baseline Assessment of 25-Hydroxyvitamin D Assay Performance: A Vitamin D Standardization Program (VDSP)...

Area of Science:

• Clinical Chemistry
• Biochemistry
• Laboratory Medicine

Background:

• Accurate measurement of total 25-hydroxyvitamin D [25(OH)D] is crucial for assessing vitamin D status.
• The Vitamin D Standardization Program (VDSP) aims to improve the comparability of 25(OH)D measurements.

Purpose of the Study:

• To evaluate the comparability of total 25(OH)D measurements in human serum across different laboratories and assay platforms.
• To assess assay performance against established VDSP criteria for accuracy and precision.

Main Methods:

• An interlaboratory study involving 15 laboratories analyzing 50 human serum samples.
• Measurement of total 25(OH)D using both immunoassays (IAs) and liquid chromatography-tandem mass spectrometry (LC-MS/MS).
• Comparison of results against target values derived from reference measurement procedures at Ghent University and NIST.

Main Results:

• Nearly all LC-MS/MS assays met the VDSP criteria for coefficient of variation (CV ≤ 10%) and mean bias (≤ 5%).
• Only 50% of immunoassays met the CV criterion, and only three of eight met the bias criterion.
• Significant variability was observed in immunoassay performance compared to LC-MS/MS.

Conclusions:

• LC-MS/MS offers superior performance and meets VDSP standardization criteria for 25(OH)D measurement.
• Immunoassays demonstrate considerable variability, highlighting the need for improved standardization and quality control.
• The study establishes a benchmark for future 25(OH)D assay evaluation and standardization efforts.