Tizianel, I.; Pagin, E.; Ragazzi, E.; Madinelli, A.; Censi, S.; Sabbadin, C.; Mantero, F.; Mian, C.; Barbot, M.; Antonelli, G.; Ceccato, F.

Background: The diagnostic accuracy of screening and confirmatory tests to differentiate primary aldosteronism (PA) among patients with low-renin hypertension (HTN) is suboptimal. We aimed to assess the role of postural stimulation test (PST) in differentiating PA from low-renin HTN. Patients and methods: Clinical and endocrine data in clinostatic position (CP) and orthostatic position (OP) during PST were evaluated in 190 hypertensive patients: 80 PA and 110 low-renin HTN. Multivariate techniques were computed: Principal Component Analysis (PCA), Partial Least Square-Discriminant Analysis (PLS-DA) and k-means clustering. Results: PST response differentiated our cohort: 96% of PA were detected in the 56/190 patients with always suppressed renin levels, 80% of patients with low-renin HTN were identified among 56/190 subjects with de-suppression of renin from CP to OP and 78/190 with always measurable renin. Increased potassium and measurable renin in OP were predictors of low-renin HTN. Cluster analysis distinguished PA from low-renin HTN: Cluster 2 included 104/110 low-renin HTN; Cluster 1 PA patients showed a higher frequency of suppressed renin levels at baseline and during PST (100% in CP and 95% in OP, respectively). Cluster 1 low- renin HTN patients had lower potassium and a higher frequency of suppressed renin levels at diagnosis and during PST, compared to Cluster 2. PLS-DA and PCA confirmed that renin in OP, renin response to PST and presence of hypokalemia were the most relevant parameters for distinguishing PA from low-renin HTN. Conclusion: Renin response during PST can be used to differentiate PA from low-renin HTN.