Endocrine Abstracts

JOINT2864

Introduction: Primary aldosteronism (PA) is an underdiagnosed cause of secondary hypertension. Diagnosis is typically performed in three steps: screening, confirmatory testing (CT), and subtype classification. Twenty-four-hour urinary aldosterone (uAldo) after an oral sodium load is one of the available confirmatory tests. This test requires an intake of 6 grams/24 hours of sodium for three days to achieve urinary sodium (uNa) >200 mmol/24 hours. However, in some cases, intravenous (IV) or oral sodium administration may have detrimental effects on the cardiovascular system.

Objective: To assess the diagnostic utility of uAldo in PA, independent of sodium loading.

Materials and methods: We carried out an observational study of patients suspected of having PA based on an aldosterone-to-renin ratio (ARR) ≧ 30 ng/dl/ng/ml/h or an aldosterone-to-direct renin concentration ratio ≧ 3.7 ng/dl per mU/l between 2018 and 2024. All patients underwent a confirmatory test (either the captopril test or IV saline infusion, depending on physician preference and/or comorbidities), and antihypertensive treatment change, and were advised to follow a normal-sodium diet for the three days preceding the confirmatory test. Additionally, uAldo and uNa were measured from a 24-hour urine sample collected the day before. The diagnostic performance of uAldo was analyzed independently of uNa levels.

Results: 77 patients were included, 47 (64.9%) of whom were women; 94.8% had hypertension. A total of 39 individuals (50.6%) had a positive confirmatory test for PA. Baseline renin was suppressed in 76.6% of patients at the beginning of the confirmatory test, and 33.8% had uNa >200 mmol/24h. The group with a negative confirmatory test had a lower median uAldo than the group with a positive confirmatory test (8.3 μg/24h, IQR [4.5–12.1] vs. 11.7 μg/24h, IQR [8.5–19.3], P <0.05). A uAldo cutoff of >6.6 μg/24h had a sensitivity of 87.1% and a specificity of 36.8%. A uAldo >14 μg/24h had a sensitivity of 46.1% and specificity of 84.2%. The area under the ROC curve (AUC) was 0.70 (95%CI 0.59–0.81).

Conclusions: uAldo, regardless of uNa levels, showed acceptable diagnostic performance. Despite the absence of prior sodium loading, most patients had suppressed renin, ensuring independent aldosterone production. A uAldo >14 μg/24h strongly suggests the diagnosis of PA in patients with a positive screening test and a normal sodium diet, while a uAldo <6 μg/24h makes PA unlikely.