Endocrine Abstracts

Introduction: PTH concentrations obtained with the second generation (2G) assays may vary widely according cross-reactivities against 7–84 PTH fragments. 1–84 bio-intact PTH is only measured with a third generation (3G) assay.

Objective: To evaluate whether the results found with a 3G method improve the classification of dialysis patients according to the KDIGO recommendations.

Patients and methods: We studied the PTH values measured in 84 hemodialysis patients’sera with a 2G immunoradiometric assay (Total intact PTH IRMA, Scantibodies) and with an automated 3G PTH (Liaison, DiaSorin). The decrease of PTH 3G levels was calculated as ((PTH 2G–PTH 3G)/PTH 2G)×100. Bone alkaline phosphatase (bAP) levels were measured using an IRMA (Beckman-Coulter; reference values: 9–14 ng/ ml).

Results: PTH results obtained with both methods were significantly correlated (r=0.97 (IC95%=0.96–0.98); P<0.000001). Patients were classified according to the KDIGOs obtained with the PTH 2G: group one: <two×upper normal limit; group two: between two×and nine×upper normal limit; group three:> nine×upper normal limit) (Table 1).

A significant correlation was seen between bAP and PTH 2G (r=0.49 (0.31–0.64); P<0.00001 or PTH 3G (r=0.46 (0.27–0.61); P<0.00001). Among the patients, 93% were classified in the same group according to the PTH 2G or 3G values.

Conclusion: The new automated PTH 3G gives the same classification in 93% of patients. Further investigations including bone biopsy would be necessary in 7% of misclassified patients to evaluate the performance of PTH 2G or PTH 3G according to the KDIGO guidelines.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.