Second and third generations of PTH immunoassays currently available on the market demonstrate significant variability with up to 4.2 fold difference in measurements depending on the method used. Such significant variability is due to differences in antibodies specificity, lack of proper calibration or potential interferences. Pre-analytical conditions, such as sampling and storage, also play significant role in stability of PTH. The measurement inconsistencies between methods, as well as pre-analytical challanges complicate establishment of treatment and prevention cutoff values. The main effort of the PTH IFCC working group is to improve calibration of currently available assays using the available reference material.
The development of mass spectrometry-based reference measurement procedure is also underway. Ideally, the reference method should allow for differentiation of intact PTH (1-84) and its fragments. Standardization of PTH will provide an opportunity for accurate diagnostic and improved pathophysiologic insight into CKD-MBD, hypo- and hyperparathyrioidism.