Moving from the second to the third generation Roche PTH assays: what are the consequences for clinical practice?

Background The determination of parathyroid hormone (PTH) is essential for exploring phosphocalcic disorders especially in patients with renal failure. At present, second or third generation PTH assays are available on the market from Roche Diagnostics as well as from others companies but the lack of standardization has complicated the interpretation. Methods We wanted to assess the clinical impact by measuring the PTH levels with the two generations concomitantly on different groups of populations including 46 healthy, 103 pre-dialyzed and 73 hemodialyzed (HD) patients. Results In healthy subjects, the PTH concentrations were not different whatever the generation used, whereas beyond 200 pg/mL, we reported an overestimation of the second generation PTH. In patients with chronic kidney disease (CKD) stage 3-5 the observed differences between the two generations increase with increasing PTH levels and decreasing glomerular filtration rate (GFR). Classification according to the kidney disease: improving global outcomes (KDIGO) revealed a high percentage of discordant results between the two generations (κ coefficient <0.20). These discrepancies are clinically relevant as PTH levels remain the cornerstone for diagnosis and treatment of the CKD-mineral and bone disorder (CKD-MBD). Conclusions The introduction of a new PTH assay generation in clinical practice should be carried out with caution.