SUN-LB95 Developing a Highly Equivalent Non-Competitive Chemiluminescence Immunoassay Aldosterone Measurement to LC/MS

Abstract

Background Measurement of plasma aldosterone and renin concentration, or activity, is useful for selecting antihypertensive agents anddetecting hyperaldosteronism in hypertensive patients. However, it takes several days to get results even if measured by inaccurateradioimmunoassay, or we must accept high-cost LC/MS, and development of a more rapid and accurate substitute has been long hoped. We havedeveloped a novel, fully-automated, high-quantitative noncompetitive chemiluminescence immunoassay (NC-CLEIA) for detecting aldosterone inserum and plasma, and its performance is evaluated as compared to LC/MS measurement. Methods Recently a unique anti-metatype antibody,which recognizes the immunocomplex of aldosterone and its monoclonal antibody, was established. Using this antibody for sensing permittedthe construction of non-competitive assay for the detection of aldosterone. The reaction protocol of novel aldosterone assay is the following. Inthe 1st reaction, aldosterone in patient’s sample is captured on anti-body coated magnetic particles. Alkaline phosphatase-conjugated antimetatypeantibody is added and incubated as 2nd reaction following a wash. Then substrate solution is added after washing immunocomplex.The resulting reaction signals are proportional to the amount of aldosterone in the sample allowing quantitative determination of in serum orplasma sample. The overall reaction is completed within 30 min. Results Limit of blank (LoB), limit of detection (LoD) and limit of quantitation(LoQ) of our NC-CLEIA aldosterone assay were 0.09 ng/dL, 0.21 ng/dL and 0.57 ng/dL, respectively. NC-CLEIA aldosterone measurements werelinearly well correlated with LC/MS aldosterone measurements (N = 130, y = 1.027x - 0.23 ng/dL, Spearman’s ρ = 0.996, P< 0.0001). Bland-Altmanplot analysis between NC-CLEIA and LC-MS/MS of aldosterone revealed a bias of 0.40 ng/dL with the limits of agreement of -4.60 and 5.41 ng/dLwith 95% confidence interval. Conclusion Our novel NC-CLEIA aldosterone assay was well-correlated and had only a very low bias with LC-MS/MSmethod and also was able to accurately quantify low level samples even in essential hypertension patients. This aldosterone assay can be a most equivalent to LC-MS/MS measurement with a low cost of 12 $ and a short measuring time of 30 minutes.