The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2018

Combination of Captopril Challenge Test and Saline Infusion Test Does Not Improve the Diagnostic Accuracy of Primary Aldosteronism (#170)

Jinbo Hu 1 , Ying Song 1 , Qifu Li 1
  1. Endocrinology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China

Context: Both saline infusion test (SIT) and the captopril challenge test (CCT) are accurate alternatives to the fludrocortisone suppression test (FST), which is generally accepted as a reliable but cumbersome confirmatory test in primary aldosteronism (PA). The combination of two independent diagnostic tests gets a higher accuracy in some diseases. However, whether a combination of CCT and SIT could improve the diagnostic accuracy of PA is still unknown.

Objective: To evaluate the diagnostic accuracy for a combination of CCT and SIT in PA diagnosis.

Methods: This study is an extension of Chongqing Primary Aldosteronism Study (CONPASS), which is a prospective study with some published results. We retrospectively recruited 164 patients with PA and 116 patients with essential hypertension (EH) who had completed FST, CCT and SIT. The post-test plasma aldosterone concentration (PAC) was used for the three confirmatory tests. The reference standard was FST, and the cut-off was set at 8 ng/dL. The index tests were CCT, SIT and a combination of CCT and SIT. Area under receiver operator characteristics curve (AUC), sensitivity and specificity were calculated.

Results: AUCs for CCT, SIT and a combination of CCT and SIT were 0.94(95% CI 0.91, 0.97), 0.95(0.91, 0.98) and 0.96(0.92, 0.98) respectively (P =0.204 for CCT vs. combination; P= 0.512 for SIT vs. combination). When the optimal cutoff of PAC post-CCT was set at 8 ng/dL and PAC post-SIT at 11 ng/dL, the sensitivity for CCT and SIT was 0.87 and 0.86 respectively, and the specificity for CCT and SIT was 0.91 and 0.92 respectively. A combination of CCT and SIT generated a sensitivity of 0.86 and a specificity of 0.92. Neither sensitivity nor specificity of the combination was significantly different from CCT or SIT.

Conclusion:. A combination of CCT and SIT does not improve the diagnostic accuracy of primary aldosteronism.