Clinical diagnostic tools for vitamin D assessment

• Published in: The Journal of steroid biochemistry and molecular biology 2018-06, Vol.180, p.105-117
• Main Authors: Shah, Iltaf, Akhtar, M. Kalim, Hisaindee, Soleiman, Rauf, Muhammad A., Sadig, Mohammed, Ashraf, S. Salman
• Format: Article
• Language: English
• Subjects: Biomarkers - blood; Chromatography, Liquid - methods; High-performance liquid chromatography; HPLC; Humans; Immunoassay; Immunoassay - methods; Immunoassays; LC/MS/MS; Mass spectroscopy; Metabolites; Osteoporosis; Rheumatoid arthritis; Tandem Mass Spectrometry - methods; Vitamin D; Vitamin D - blood; Vitamin D Deficiency - blood; Vitamin D Deficiency - diagnosis; Vitamin deficiency; Vitamins - blood
• ISSN: 0960-0760; 1879-1220
• DOI: 10.1016/j.jsbmb.2017.10.003

[Display omitted] •Immunoassays are rapid, high throughput offering excellent sensitivity of 3.4–156ng/ml, but cannot distinguish between forms of vitamin D.•HPLC based assays are cheaper and cost-effective, but they are not very sensitive for minor Vitamin D metabolites.•LC/MS/MS also provides excellent sensitivity, wide dynamic range from 0.068pg/ml to 100ng/ml, along with accurate metabolite identification.•A huge limitation with LC/MS/MS is their poor throughput for sample analyses making them impractical for rapid, large-scale analyses.•Recently, attention has been focused on accurately measuring various active and inactive epimers and isobars of vitamin D. Vitamin D deficiency has been implicated in a plethora of diseases including rheumatoid arthritis, Parkinson’s disease, Alzheimer’s disease, and osteoporosis. Deficiency of this vitamin is a global epidemic affecting both developing and developed nations. Within a clinical context, the qualitative and quantitative analysis of vitamin D is therefore vital. The main metabolic markers for assessing vitamin D status in humans are the hydroxylated forms of vitamin D, 25OHD3 and 25OHD2 on account of their long half-lives within the body and excellent stability. An adequate level for healthy individuals of these hydroxylated forms is estimated to be around 20–40ng/ml of blood. There are three main analytical techniques for determining the levels of 25OHD3 and 25OHD2. The first technique is immunoassay-based and can be performed in a rapid, high throughput, automated manner, allowing as many as 240 tests per hour with the duration of each assay as little as 18min. Furthermore, it offers excellent sensitivity with a detection range of 3.4–156ng/ml. A major downside of immunoassays is that they are unable to distinguish between the various forms of vitamin D. While HPLC is a highthroughput low cost instrument it is not a very sensitive technique and cannot quantify the down stream metabolites of vitamin D. The third technique, namely liquid chromatography-mass spectrometry (LC–MS/), provides excellent sensitivity with a wide dynamic range from 0.068pg/ml to 100ng/ml. Additionally, it offers a high level of separation and permits identification of vitamin D-related metabolites. However, a huge limitation with LC/MS/MS is their poor throughput for sample analyses. As yet, there is no analytical technique which combines the fine detection capabilities of LC/MS/MS and the rapid, automated format of immunoassay,