The Diagnostic Value of Captopril Challenge Test for Primary Aldosteronism

  Objective  To investigate the diagnostic value of different captopril challenge test (CCT) diagnostic criteria for diagnosing primary aldosteronism (PA).

  Methods  We collected the clinical data of 184 patients with hypertension retrospectively in West China Hospital of Sichuan University. Receiver operating characteristic (ROC) curves were used to analyze the post-CCT efficacy of aldosterone renin activity ratio (ARR), plasma aldosterone concentration (PAC), plasma renin activity (PRA) and PAC suppression rate for PA diagnosis.

  Results  This study included 125 cases of primary aldehyde (PA group) and 59 cases of essential hypertension (EH group), and there were 38 normal renin primary hypertension (NREH group) and 21 low renin primary hypertension (LREH group) in EH group. The post-CCT PAC suppression rate (median (P₂₅, P₇₅)) of EH and PA group were 0.190 (0.083, 0.351) and 0.125 (0.024, 0.237), respectively. Compared with the NREH group, the basic and post-CCT PRA of LREH group were lower (P<0.001), and there were no significant differences compared with the PA group (P>0.05). We found significant overlap of post-CCT PRA and ARR between PA group and LREH group, while the overlap of post-CCT PAC between the two groups was small. In differential diagnosis of PA and EH, the areas under ROC curve of the post-CCT ARR, PAC, PRA and PAC suppression rate were 0.860 (95% confidence interval (CI): 0.800-0.907), 0.881 (95%CI: 0.825-0.924), 0.771 (95%CI: 0.703-0.831) and 0.632 (95%CI: 0.558-0.701), respectively. There was no significant difference between the first two indexes (Z=0.443, P=0.658), and both of them were higher than the latter two (P<0.05). The optimal post-CCT cut-off values for ARR and PAC in differential diagnosis of PA and EH were 19.24 ng·dL⁻¹ with a sensitivity of 78.4% and a specificity of 88.1%, and 32.47 (ng·dL⁻¹)/(ng·mL⁻¹·h⁻¹) with a sensitivity of 84.17% and a specificity of 72.41%.

  Conclusion  Both ARR and PAC have higher diagnostic value than the post-CCT PAC suppression rate, post-CCT PAC is especially suitable as a confirmatory testing criterion of PA.