Comparison of the Elecsys PTH(1-84) assay with four contemporary second generation intact PTH assays and association with other biomarkers in chronic kidney disease patients

Abstract

Objectives: The COBAS Elecsys PTH(1-84) assay is a novel, electro-chemiluminescence immunoassay that exclusively measures full-length parathyroid hormone (PTH). The aim of this study is to compare the automated biointact Elecsys PTH(1-84) assay with four contemporary, iPTH assays in chronic kidney disease (CKD) patients.

Design and methods: We compared the Elecsys PTH(1-84) assay with four iPTH assays (Siemens ADVIA Centaur, Ortho Clinical Diagnostics (OCD) VITROS, Beckman Access2, Abbott ARCHITECT) in the measurement of PTH in 83 local CKD patients. Majority of the patients (44) had CKD but were not on dialysis, 15 were on hemodialysis, 15 were on peritoneal dialysis, and 9 were post-renal transplant. The precision performance and correlation of the assays were determined. PTH(1-84) concentrations were correlated with calcium, phosphate, alkaline phosphatase, hemoglobin, HbA1c and lipid concentrations.

Results: The Elecsys PTH(1-84) assay showed comparable precision and good correlation with the iPTH assays. Although the four different iPTH assays correlated well with each other, there was significant discrepancy among assays. The discrepancy among assays increased with increasing PTH concentrations. The ADVIA Centaur and ARCHITECT assays measured significantly higher PTH concentrations than the VITROS and Access2 assays. PTH(1-84) showed a positive association with phosphate and alkaline phosphatase and an inverse association with HbA1c. There was no significant association with lipid concentrations.

Conclusions: The third generation Elecsys PTH(1-84) assay had comparable precision performance and correlated well with second generation iPTH assays. However, significant discrepancy was found among the four iPTH assays in measuring iPTH in CKD patients.