Postural test to differentiate primary aldosteronism from low-renin hypertension: a retrospective single-center study

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 the 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 with PA and 110 with 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 during PST, 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. Normal 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 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.