Role of postural test in differentiating primary aldosteronism from low renin hypertension

Background: The diagnostic accuracy of screening procedures and confirmatory tests is suboptimal to differentiate primary aldosteronism (PA) among patients with low-renin hypertension (HTN) is challenging. Our aim was to assess the role of postural stimulation test (PST, previously used for PA subtyping) in differentiating PA from low-renin HTN.
Patients and methods: Clinical and endocrine data in clinostatic position (CP) and orthostatic position (OP) 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 showed 56/190 patients with suppressed renin levels in CP and OP (54/56 were PA), 56/190 with de-suppression of renin from CP to OP (45/56 were low-renin HTN), and 78/190 with renin measurable in CP and OP. Increased potassium and measurable renin in OP were predictors of low-renin HTN. Cluster analysis distinguished PA from low-renin: 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 exclude PA among patients with low-renin HTN.