Abstract P305: New Screening Cutoff Values For Detection Of Aldosteronoma Examined By Lc-ms/ms And A Newly Developed Non-competitive Chemiluminescent Enzyme Immunoassay

Abstract

Thinking of the poor accuracy of CLEIA and RIA measurements of plasma aldosterone concentrations (PACs), LC-MS/MS is the ideal method but it is costly, labor intensive and time consuming. A novel non-competitive CLEIA (NC-CLEIA) for measuring PACs was recently developed. We validated the accuracy and diagnostic ability of the NC-CLEIA as compared to PACs measured by LC-MS/MS and also determined the screen cutoffs by both measurements, respectively, detecting aldosterone-producing adenoma (APA) in hypertensive patients. Method: We measured plasma renin activity by enzyme assay and PACs using LC-MS/MS and NC-CLEIA in 133 APA, 100 bilateral hyperaldosteronism and 111 essential hypertension patients to examine the accuracy of PACs by this NC--CLEIA as compared with those by LC-MS/MS, and determine the screen cutoffs to detect APA. Passing-Bablok analysis revealed that NC-CLEIA (the regression slope, the intercept and the correlation coefficient were 0.962, -0.043, and 0.994, respectively), was significantly correlated and very equivalent to LC-MS/MS. Bland-Altman plot analysis of NC-CLEIA by LC-MS/MS also demonstrated much smaller systemic errors (a bias of -0.348 ng/dL with limits of agreement of -4.390 and 3.694 and 95% confidence interval) than those . The receiver-operating characteristics analysis demonstrated that cut-offs of aldosterone/renin activity ratio obtained by LC-MS/MS and NC-CLEIA were 31.2 and 31.5 (ng/dL per ng/mL/hr) with a sensitivity of 91.0% and 90.2%, and a specificity of 75.4% and 76.8%, respectively, to differentiate APA from non-APA. This novel NC-CLEIA for PAC could serve as a clinically reliable alternative to LC-MS/MS.