[Re-evaluation of the diagnostic value and optimal cutoff point of captopril challenge test in diagnosis of primary aldosteronism].

Objective: The aim of the present study was to re-evaluate the diagnostic value and optimal cutoff point of captopril challenge test (CCT) in diagnosis of primary aldosteronism (PA). Methods: This is a retrospective study. All patients with a high risk for PA underwent screening test, and then proceeded to CCT and fludrocortisone suppression test (FST) on different days. The FST was used as a reference standard for PA. The plasma renin concentration (PRC) and plasma aldosterone concentration (PAC) were measured with an automated chemiluminescence immunoassay. Random number method was performed in the patients with unilateral primary aldosteronism (UPA), in order to make the proportion of the analyzed UPA in PA was 35%. Receiver operating characteristic (ROC) analyses were performed to compare diagnostic accuracy. Results: A total of 543 patients with 400 PA patients and 143 essential hypertension (EH) patients were enrolled. The diagnostic value of post-CCT PAC was significantly higher than that of the post-CCT plasma aldosterone-renin ratio (ARR), and that of the PAC suppression percentage, respectively. The area under the ROC curve (AUC _ROC ) was 0.86 (0.83, 0.89) for PAC, 0.78 (0.74, 0.82) for ARR, and 0.62 (0.56, 0.67) for the PAC suppression percentage (all P <0.01), respectively. The optimal cutoff point of post-CCT PAC for PA was 110 ng/L, in which the sensitivity and specificity were 73.25% and 79.02%, respectively. The diagnostic efficiency of post-CCT PAC was not improved either in combination with PAC suppression percentage or in combination with post-CCT ARR. Conclusions: CCT is a useful test for the confirmation of PA. PAC level of 110 ng/L at 2 h after 50 mg of captopril is recommended as an optimal cutoff point for the diagnosis of PA.