Endocrine Abstracts

Background and aim: Aldosterone-to-Renin Ratio (ARR) is recommended as initial test to screen for Primary Aldosteronism (PA), especially in high-risk hypertensive population. Endocrine Society (ES) Guidelines recommend that patients with an increased ARR should undergo one or more confirmatory tests in order to confirm or exclude PA diagnosis. Captopril Challenge Test (CCT) and Saline Infusion Test (SIT) are commonly used in routine clinical practice. The aim of our study was to evaluate the diagnostic accuracy of CCT and SIT in a large series of hypertensive patients with increased ARR.

Materials and methods: We retrospectively analysed data of 230 CCT and 120 SIT of 272 hypertensive patients (95 with PA and 177 with essential hypertension [EH]) with increased basal ARR (>30 ng/dL/ng/ml/h or >91 pmol/L/mU/L). Aldosterone was measured with radioimmunometric assay (RIA) and ARR calculated with Plasma Renin Activity (PRA) until April 2015; then Aldosterone was measured with electrochemiluminescence assay (ECLIA) and ARR calculated with Direct Renin Concentration (DRC). The accuracy of post-CCT ARR and post-SIT plasma aldosterone values for confirming PA was estimated with the area under the receiver operator curve (ROC), performed with SPSS, significance set at P<0.05.

Results: The median of post-CCT ARR, calculated both with PRA and with DRC, and post-CCT plasma aldosterone values, both in RIA and in ECLIA, were significantly higher in PA than in EH, as expected (P<0.001). Even the median of post-SIT plasma aldosterone values, both in RIA and in ECLIA, were significantly higher in PA than in EH (P<0.001). The ROC of post-CCT ARR and post-SIT plasma aldosterone values were 0.839 and 0.888, respectively, showing comparable diagnostic accuracy with a sensitivity of 75.8% and 83.3% and a specificity of 84.6% and 89.2, respectively. The optimal post-CCT ARR cutoff for identifying PA was 31 ng/dL/ng/ml/h, while the optimal plasma aldosterone cutoff value was 15.8 ng/dL post-CCT and 7 ng/dL post-SIT.

Conclusions: Post-CCT ARR, post-CCT and post-SIT plasma aldosterone values were all reliable for PA diagnosis, showing comparable diagnostic accuracy, especially to exclude rather than to confirm the PA. The optimal cutoffs were in line with those recommended by the ES.