Intact and bioactive PTH values are strongly correlated in kidney transplant recipients

This study aims to evaluate the correlation between parathyroid hormone measured by a second-generation assay (PTHG2) and by a third-generation assay (PTHG3), and their association with mineral and bone disorder (MBD) biochemical parameters and radiographic vascular calcification score in kidney transplant recipients (KTRs).

We evaluated 87 KTRs and measured PTHG2, PTHG3, biochemical profile, urinary fractional excretion of calcium (FE Ca) and phosphate, 25(OH)D3, and Kauppila score for vascular calcification. Statistical analysis: Non-parametric tests and logistic regression analysis were performed. The significance level was set to 5%.

In our population, the mean age was 54 years, the mean time after transplantation was 9.4 years (± 7.6), and the mean estimated glomerular filtration rate (GFR, calculated using the Chronic Kidney Disease Epidemiology Collaboration equation - CKD-EPI) was 59.1 mL/min/1.73 m2. The correlation between PTHG2 and PTHG3 was almost perfect (r = 0.99; 95% CI = 0.98-0.99) and there was no significant difference between the PTHG2/PTHG3 ratio from different KTR-CKD stages. Investigating the association among PTH and the MBD biochemical profile, there was only correlation between PTH and FE Ca (p-value 0.01).

We concluded that there is no advantage in PTHG3 dosage over PTHG2 measurement in this population.