Accurate measurement of parathyroid hormone (PTH) concentrations is of great importance, especially for patients with parathyroid disorders and for monitoring bone turnover in individuals with chronic kidney disease and mineral bone disorders. There are currently two generations of PTH immunoassays (IA) on the market, which suffer from cross-reactivity and lack of standardization. Other techniques, such as liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), are being explored as potential next-generation assays with unprecedented specificity and sensitivity.
In our group, we have developed and validated the first LC-MS/MS method with antibody-free sample preparation to become a candidate reference assay for 1-84 PTH. Separation and quantification of full-length 1-84 PTH was performed on a Shimadzu Nexera X2 UPLC coupled to a Sciex QT6500 MS. LC was performed on an Acquity UPLC BEH C4 300Å column using a water-acetonitrile mobile phase gradient containing 0.4% formic acid and 5% dimethyl sulfoxide. MS multiple reaction monitoring recorded 3 transitions for PTH and its isotopically labeled internal standard for specificity.
The method was validated according to the Clinical and Laboratory Standards Institute C-62A guidelines.
This validated method was also used to recalibrate the results obtained from the IA. The results of this recalibration will be discussed. Finally, ongoing work in our group and future perspectives will be discussed.
