Comparison Between Two Different Second-Generation Parathyroid Hormone Assays

Abstract

Background: Accurate measurement of parathyroid hormone (PTH) levels is crucial for the diagnosis and treatment of hyperparathyroidism and hypoparathyroidism. Given the existence of various PTH forms in the bloodstream, it is well-known that there are variations in PTH levels depending on the measurement method. This study aimed to evaluate two different second-generation PTH assays. Methods: A total of 56 residual samples originally requested for PTH testing were utilized for comparing the two methods. Each sample was subjected to analysis using an immunoradiometric assay (ELSA-PTH; Cisbio Bioassays, France) and a chemiluminescence microparticle immunoassay (Alinity i Intact PTH; Abbott, USA). Precision and linearity were analyzed, and reference interval and limit of quantitation (LoQ) were verified to investigate the performance of the Alinity i Intact PTH assay. Results:The median PTH values of ELSA-PTH and Alinity i Intact PTH were 69.0 pg/mL and 101.9 pg/mL, respectively, with significantly higher PTH values for Alinity i Intact PTH (P < 0.0001). The Pearson correlation coefficient was 0.959, and the average difference between the two tests was 78.57 pg/mL. For Alinity i Intact PTH, the coefficient of variation obtained at three concentrations was 1.9%, 2.4%, 1.8% for repeatability, and 2.0%, 2.7%, 2.7% for within-laboratory precision. Linearity was observed in the range of 3-3,000 pg/mL. The reference interval and LoQ reported by the manufacturer were verified. Conclusions: The PTH results of the ELSA-PTH and Alinity i Intact PTH assays showed a strong correlation, and the Alinity i Intact PTH assay demonstrated acceptable analytical performance.