BackgroundCurrent guidelines recommend use of the aldosterone‐renin ratio (ARR) for the case detection of primary aldosteronism followed by confirmatory tests to exclude false‐positive results from further diagnostic workup. We investigated the hypothesis that this could be unnecessary in patients with a high ARR value if the quantitative information carried by the ARR is taken into due consideration.Methods and ResultsWe interrogated 2 large data sets of prospectively collected patients studied with the same predefined protocol, which included the captopril challenge test. We used an unambiguous diagnosis of aldosterone‐producing adenoma as reference index. We also assessed whether the post‐captopril ARR and plasma aldosterone concentration fall furnished a diagnostic gain over baseline ARR values. We found that the false‐positive rate fell exponentially, and, conversely, the specificity increased with rising ARR values. At receiver operating characteristics curves and diagnostic odds ratio analysis, the high baseline ARR values implied very high positive likelihood ratio and diagnostic odds ratio values. The baseline and post‐captopril ARR showed similar diagnostic accuracy (area under the receiver operating characteristics curve) in both the exploratory and validation cohorts, indicating lack of diagnostic gain with this confirmatory test (between‐area under the curve difference, 0.005; 95% CI, −0.031 to 0.040; P=0.7 for comparison, and 0.05; 95% CI, −0.061 to 0.064; P=0.051 for comparison, respectively).ConclusionsThese results indicate that the ARR conveys key quantitative information that, if properly used, can simplify the diagnostic workup, resulting in saving of money and resources. This can offer the chance of diagnosis and ensuing adrenalectomy to a larger number of hypertensive patients, ultimately resulting in better control of blood pressure.