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

## TL;DR

This study finds that two parathyroid hormone tests give similar results in kidney transplant patients and are strongly linked.

## Contribution

The study demonstrates that PTHG3 offers no additional benefit over PTHG2 in kidney transplant recipients.

## Key findings

- PTHG2 and PTHG3 measurements are almost perfectly correlated (r = 0.99) in kidney transplant recipients.
- PTH levels are significantly correlated with urinary fractional excretion of calcium (p-value 0.01).
- No significant difference was found in PTHG2/PTHG3 ratios across different kidney disease stages.

## Abstract

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.