Most clinical laboratories use immunoassays routinely to measure 25-hydroxyvitamin D (25OH D) in serum. The metabolites of vitamin D are important in the regulation of calcium and bone metabolism.
Example of MS platforms developed for routine clinical testing Immunoassays are high throughput, and relatively cheap and easy to use, but have some important limitations. It has been found that immunoassays have problems recognising vitamin D2 after it has been ingested, giving a significant under-estimation of the concentration of 25OH D2 . This has an impact on the total 25OH D measured, potentially leading to misdiagnosis.
Misdiagnoses of vitamin D deficiencies
Source: European Hospital