ORF31-03 - Clinically Relevant Aldosterone Variability Persists Despite Control for Medication and Potassium: Implications for the Diagnosis of Primary Aldosteronism

Background
Intraindividual variability in aldosterone has been reported in primary aldosteronism (PA) and may lead to false-negative screening results. However, whether this variability persists after accounting for medication effects and potassium status, and whether this condition is associated with clinical characteristics and disease subtype, remains limited.

Methods
We conducted a retrospective study of PA patients who underwent at least two plasma aldosterone measurements on different days at King Chulalongkorn Memorial Hospital, Bangkok, Thailand, between 2021 and 2025. The primary outcome was the proportion of patients with at least one plasma aldosterone concentration (PAC) below diagnostic thresholds ( < 10 ng/dL). Sensitivity analyses were performed after excluding patients on potentially interfering antihypertensive medications and those with hypokalemia. Secondary outcomes included associations between aldosterone variability and clinical characteristics, PA subtype, and treatment.

Results:
Among 110 patients, 21 (19%) had at least one PAC < 10 ng/dL. Patients underwent a median of two PAC evaluations (IQR 2–3). The mean age was 55 years, and 52% were male. Hypertension and hypokalemia were present in 98% and 87%, respectively. After excluding patients on potentially interfering antihypertensive agents (n= 92), 17 (18.5%) had PAC < 10 ng/dL at least once. After excluding those with hypokalemia (n= 109), 19 (17%) had PAC < 10 ng/dL at least once. When excluding both medication interference and hypokalemia (n= 85), 14 (16.5%) still demonstrated PAC below threshold at least once. Clinical presentation and PA subtype did not differ between patients with consistently elevated PAC and those with PAC < 10 ng/dL at least once. Notably, among 12 patients with at least one PAC < 10 ng/dL who underwent adrenal venous sampling (AVS), 7 (58%) demonstrated lateralizing PA.

Conclusion:
Nearly 20% of PA patients had at least one PAC value below the guideline-recommended diagnostic threshold of 10 ng/dL, and this variability persisted despite excluding patients with potential medication interference or hypokalemia. Notably, a substantial number of these individuals had lateralizing disease amenable to curative surgery. Strict adherence to guideline-recommended diagnostic thresholds for PA may risk erroneous exclusion of the diagnosis, including of lateralizing disease. Liberalizing diagnostic thresholds and/or repeat testing should be considered to maximize case detection.