Assessment of the Quantitative Value Usefulness of the Aldosterone-Renin Ratio (ARR) for Primary Aldosteronism (AQUARR) Study.

Current guidelines recommend use of the aldosterone-renin ratio (ARR) for the case detection of primary aldosteronism (PA), the most common cause of secondary hypertension, in selected hypertensive patients. "Confirmatory" tests are then recommended in patients who tested positive at the ARR to exclude from further diagnostic work-up false positive results. Based on our experience we hypothesized that the ARR carries quantitative information, which can avoid the need of confirmatory tests. We herein describe a study protocol to identify the ARR cut-off value with a high specificity for the exclusion of aldosterone-producing adenoma (APA) based on analysis of two large prospectively collected datasets of patients in which a conclusive diagnosis of APA was made by the four corners criteria. This will also serve to investigate the diagnostic gain provided over this ARR cut-off value by one confirmatory test, the captopril challenge test. Hence, with this protocol we expect to identify an ARR cut-off value that might prevent further testing in patients with either a low or a high probability of APA. This could translate in a higher diagnostic accuracy and, by preventing unnecessary invasive testing, into a substantial saving of money, time, and resources.