Evaluation Of Chemiluminescence Immunoassay For Detecting Blood Levels Of Aldosterone And Renin With Its Diagnostic Value Of Primary Aldosteronism With Comparison To Radio Immunoassay

Background:Hypertension,as one of the leading killers of the cardiovascular disease,is highly valued by medical workers.Primary aldosteronism(PA)is the most common cause of secondary hypertension which can be cured,the present rate of screening is very low.PA has a much higher cardiovascular and renal complications risk profile than age-,sex-,and blood pressure-matched essential hypertension.Increased aldosterone is an important risk factor for ventricular hypertrophy,arrhythmia,stroke,and impaired renal function.Furthermore,specific treatments are available that ameliorate the impact of this condition on important patient outcomes.This research aims to evaluate chemiluminescence immunoassay(CLIA)for detecting blood levels of aldosterone and renin with its screen rate of primary aldosteronism(PA)with comparison to radio immunoassay(RIA).Methods:The 151 patients for case detection of PA in the First Affiliated Hospital of DaLian Medical University from March 2016 to October 2016 were enrolled in this study.Before they admitted into the hospital,all of the patients made preparations for the case detection according to the The Management of Primary Aldosteronism by Chinese Society of Endocrinology(CSE)in 2016,including a washout of all interfering antihypertensive medications.We collected the acquisition history and completed the biochemical examinations.We examined plasma rennin activity(PRA)or direct rennin concentration(DRC)and plasma aldosterone concentration(PAC)by both RIA and CLIA,and then completed the saline infusion test.According to the guideline,all patients were divided into two group,essential hypertension group(EH)and primary aldosteronism group(PA).SPSS 20.0 statistical software for processing and analyzing the data.We compare DRC which measured by chemiluminescence vs.PRA which measured by RIA and aldosterone which measured by chemiluminescence vs.RIA which measured by RIA with correlation analysis(Spearman’s ’R’ correlation test).To assess the diagnostic accuracy of ADRR(PAC to DRC ratios by CLIA)and ARR(PAC to PRA ratios by RIA)for PA diagnosis,we used receiver operator characteristics(ROC)curve and calculated the area under the curve(AUC),then found out the best cut-off value through the Youden’s index.Thevalue of Z was calculated by MedCalc Software 15.6.Results:1.Description of the population:In the analysis of the clinical data of PA group and EH group,we find the age and course of hypertension have statistical significance(P<0.05).The serum potassium concentration in PA group were lower than EH group(P<0.01).The urinary potassium concentration of 24hours in PA group were higher than EH group(P<0.01).The urinary micro albumin to creatinine ratios(MA/CRE)in PA group were lower than EH group.The serum sodium concentration,urinary sodium concentration of 24hours,mean diastolic blood pressure,mean systolic blood pressure,heart rate,BMI,FMD showed no difference.2.Comparison between direct rennin concentration and plasma rennin activity:In our cohort of patients median DRC by CLIA was 10.38pg/ml in EH group and 1.06pg/ml in PA group.The median PRA by RIA was 1.23 ng/(L·h)in EH group and 0.2 ng/(L h)in PA group.The same method was used to detect the PRC(DRC),PA group were much lower than EH group(P<0.01).We compared DRC by CLIA with PRA by RIA to assess the within-patient correlation.It showed a significant correlation(r=0.951,P<0.01).After conversion of the data to natural logarithms to obtain a normal distribution we performed a linear regression(R2=0.818 in EH group;R2=0.592 in PA group).3.Comparison between plasma aldosterone concentrations in CLIA and RIA:In this research the median plasma aldosterone concentration(PAC)measured by CLIA was 68.2 pg/ml in EH group and 128.5 pg/ml in PA group.The median PAC measured by RIA was 102.72 pg/ml in PA group and 68.62 pg/ml in EH group.The same method was used to detect the PAC,PA group were much higher than EH group(P<0.01).We compared PAC by CLIA with PAC by RIA to assess the within-patient correlation.It showed a significant correlation(r=0.862,P<0.01).After conversion of the data to natural logarithms to obtain a normal distribution we performed a linear regression(R2=0.644 in EH group;R2=0.804 in PA group).4.CLIA vs.RIA performance on screening test for PA:To assess the diagnostic accuracy of the two assay we used receiver operator characteristics(ROC)curves.The area under the curve(AUC)for upright ADRR was 0.913(95%CI 0.857-0.953).And upright ADRR using as cut-off levels was 31(pg/ml)/(μIU/ml)meanwhile the Youden’s index was 0.71.We considered that the screening test by CLIA has certain accuracy.The area under the curve(AUC)for upright ARR was 0.896(95%CI 0.836-0.940).And upright ARR using as cut-off levels was 260(pg/ml)/(ng/ml/h)meanwhile the Youden’s index was 0.70.We considered that the screening test by RIA has a lower accuracy than CLIA.There was no difference between these two assays(Z=1.15,P=0.25).Conclusions:1.CLIA and RIA have a good correlation to detect renin concentration(activity)and plasma aldosterone concentration as well as case detection of PA.CLIA has the superiority of simple performance,less time-consuming,good reproducibility and without radioactive contamination.CLIA is more suitable for clinical use instead of RIA.2.CLIA compared with RIA has higher sensitivity and specificity in the PA screening.