Diagnostic performance of 24-hour urinary aldosterone for primary aldosteronism in patients with or without discontinuation of antihypertensive medications.

Primary aldosteronism (PA) is the most common form of secondary hypertension. However, its diagnosis is complicated by the need to withdraw interfering antihypertensive medications. Traditionally, 24-h urinary aldosterone (Uald) level measurement is employed as part of the oral sodium loading test to diagnose PA. However, the diagnostic efficacy of 24-h Uald for PA under a usual diet and without drug washout remains unclear. This retrospective study enrolled 583 patients with essential hypertension (EH) and 259 patients with PA, as well as an external validation cohort comprising 157 hypertensive patients. Patients with unilateral PA presented higher 24-h Uald levels than those with bilateral PA. Combination antihypertensive therapy reduced 24-h Uald levels in both EH and PA groups. Receiver operating characteristic curve analysis revealed similar areas under the curve for 24-h Uald diagnosing PA between the off-medication group (0.879, 95% CI = 0.834-0.925) and the on-medication group (0.851, 95% CI = 0.817-0.886). The optimal 24-h Uald cut-offs for PA diagnosis were 9.57 μg (sensitivity 79.4%, specificity 88.6%) in the off-medication group and 8.41 μg (sensitivity 75.8%, specificity 79.4%) in the on-medication group, with closely matched thresholds observed between patients receiving renin-increasing medications (8.52 μg) and those on combined renin-increasing and renin-suppressing therapy (8.39 μg). The diagnostic accuracy of 24-h Uald reached 89.2% in the external validation cohort. Our research indicates that the 24-h Uald test is clinically feasible for diagnosing PA without additional sodium supplementation or drug washout. However, the diagnostic threshold for 24-h Uald should be adjusted downward in patients on medications.