Evaluating 24-h Urine Aldosterone Levels as a Practical Diagnostic Tool for Primary Aldosteronism

Background/Objectives: This study aimed to evaluate the diagnostic utility of 24 h urinary aldosterone (uAldo) measurements in patients with suspected primary aldosteronism (PA) and to explore its potential utility in guiding individualized clinical decisions. Methods: We examined 40 patients with suspected PA who underwent screening, confirmatory testing and 24 h uAldo assessment at a tertiary endocrinology center. Confirmatory tests were performed per standardized protocols. Patients were classified into three groups based on uAldo levels derived from receiver operating characteristic (ROC) analysis: Group 1 (<8.7 μg/24 h), Group 2 (8.7-13.6 μg/24 h), and Group 3 (>13.6 μg/24 h). Diagnostic performance was evaluated using sensitivity, specificity, and area under the curve (AUC). Results: uAldo levels were significantly higher in patients with positive confirmatory tests (16.3 μg/24 h vs. 5.5 μg/24 h, p < 0.001). A cut-off of >8.7 μg/24 h showed 89% sensitivity and 91% specificity (AUC: 0.95), while >13.6 μg/24 h yielded 91% sensitivity and 86% specificity (AUC: 0.97). Patients in Group 2 were managed solely with medical therapy, with no need for invasive procedures. Group 3 patients had higher blood pressure, higher uAldo levels, and more frequent hypokalemia. Adrenal venous sampling and surgery were more common in Group 3, with histological PA confirmation in all operated patients. Conclusions: The 24 h uAldo measurement demonstrated promising diagnostic performance in this cohort. The proposed cut-offs may help support patient stratification and clinical decision-making in patients with suspected PA. However, because confirmatory testing served as the reference standard, these findings should be considered exploratory and require external validation in larger multicenter studies before incorporation into routine diagnostic algorithms.