Development and validation of a novel chemiluminescent immunoassay for diagnosing primary aldosteronism

Purpose: To compare the diagnostic accuracy of plasma aldosterone concentration (PAC), plasma renin activity (PRA) and aldosterone-to-renin ratio (ARR) in primary aldosteronism (PA) using radioimmunoassay (RIA) and chemiluminescence immunoassay (CLIA) methods. Methods: Both RIA and CLIA were used to analyze the PAC, PRA and ARR with subjects in standing or supine position, before and after a saline infusion test (SIT). The correlation between RIA and CLIA was measured by regression analysis. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic accuracy by RIA and CLIA. Results: A positive correlation was found between PAC and PRA after SIT using RIA and CLIA (0.1745 and 0.3085, respectively). A positive correlation was found between the PAC and PRA in standing and supine position using RIA and CLIA (0.3979 vs 0.2399 and 0.1885 vs 0.4032, respectively). There was no obvious difference in AUCs of PAC, PRA, and ARR between RIA and CLIA (PAC: 0.91 vs. 0.89; PRA: 0.88 vs. 0.87; ARR: 0.93 vs. 0.92). In standing posture, the AUCs of PAC, PRA and ARR using RIA were 0.63, 0.72 and 0.78, respectively, and the results of CLIA were 0.65, 0.75 and 0.82, respectively. In supine posture, the AUC of PAC, PRA and ARR using RIA was 0.65, 0.68 and 0.71, respectively, and the results of CLIA were 0.68, 0.70 and 0.79, respectively. Conclusion: Chemiluminescent assay is reliable for diagnosis of PA when compared with radioimmunoassay