Endocrine Abstracts

Objective: Primary aldosteronism (PA) has emerged as the most frequent form of secondary hypertension. For the diagnosis of PA, confirmatory testing is indispensable and different tests are recommended by guidelines, including captopril challenge test (CCT) and saline infusion test (SIT). However, there are sparse studies evaluating and comparing CCT and SIT in Chinese population. Hence, we investigate the diagnostic efficiency of CCT and SIT for PA in Chinese hypertensives in our study.

Methods

In total, 183 patients with essential hypertension and 105 patients with PA were recruited in the study, and their clinical data were analyzed by constructing the receiver operating characteristics (ROC) curve to compare the accuracy of CCT and SIT.

Results: (1) A total of 277 patients underwent CCT. The AUC of post-CCT aldosterone, aldosterone suppression rate and post-CCT aldosterone/renin ratio (ARR) were 0.877 (95% CI 0.833 to 0.921, P<0.001), 0.683 (95% CI 0.617 to 0.748, P<0.001) and 0.929 (95% CI 0.896 to 0.963, P<0.001), and accuracy of ARR post-CCT is highest (P<0.001). For post-CCT ARR, at the optimal cut-off value of 30 ng•dl-1/ng•ml-1•h-1, the sensitivity and specificity were 67.6% and 96.2% respectively. (2) The SIT was performed in 116 patients. The AUC of post-SIT aldosterone and post-SIT ARR were 0.829 (95% CI 0.731 to 0.928, P<0.001) and 0.923 (95%CI 0.860 to 0.985, P<0.001), and post-SIT ARR has higher accuracy (P<0.05). The best cut-off value of post-SIT ARR for identifying PA was 60 ng•dl-1/ng•ml-1•h-1, with sensitivity and specificity of 81.8% and 95.2%, respectively. (3) 110 patients underwent both CCT and SIT. In the consistency check of CCT and SIT, kappa value was 0.714, P<0.001. The AUC of post-CCT ARR, post-SIT ARR, serial test of post-CCT ARR and post-SIT ARR were 0.937 (95% CI 0.885 to 0.990, P<0.001), 0.921 (95% CI 0.858 to 0.984, P<0.001) and 0.939 (95% CI 0.881 to 0.881, P<0.001), there is no statistical difference among the three indices.

Conclusions: With a good consistency, CCT and SIT are both efficient confirmatory tests for PA, and applying ARR post-CCT or ARR post-SIT make it feasible to diagnose PA more accurately. However, combining two tests fails to further improve the accuracy for diagnosis of PA.