Endocrine Abstracts

JOINT1578

Introduction: Primary aldosteronism (PA) is a common cause of endocrine hypertension, yet there are some difficulties in diagnosing the disease. A single normal or low aldosterone/plasma renin activity (PRA) ratio (ARR) alone may not be sufficient to exclude the diagnosis of primary aldosteronism (PA) (3–5). The saline infusion test (SIT), a standard confirmatory test, has limitations such as contraindications, need for hospitalization and high cost (6). This study evaluates the potential of the plasma aldosterone/potassium (A/K) ratio in predicting PA.

Methods: Between 2019 and 2023, 118 patients admitted to our Endocrinology outpatient clinic who underwent SIT with a prediagnosis of PA due to hypertension, as well as hypokalemia and/or elevated ARR were retrospectively included in the study. Patients who were pregnant, <18 years of age, had adrenal surgery and used diuretics were excluded. Demographic data, laboratory and adrenal imaging results were evaluated retrospectively. Aldosterone and concurrent potassium levels at the time of admission were obtained and A/K ratio was calculated. The diagnosis of PA was made according to the results of SIT, captopril confirmation test if available, adrenalectomy results and clinical judgment of the multidisciplinary council (7). All parameters were compared between the groups of patients with and without PA.

Results: A total of 118 patients who underwent SIT were included in the study. PA was diagnosed in 57 patients based on clinical and laboratory results. Male sex ratio was higher in the PA group (52.6% vs. 23.0%; P=0.001) (Table 1). Patients with PA had higher aldosterone levels (P<0.001) and ARR (P<0.001), but lower potassium levels (P<0.001) and PRA (P=0.01). The A/K ratio was significantly higher in the PA group (P<0.001). ROC analysis showed that an A/K ratio cut-off of 5.4 could distinguish PA patients from non-PA patients [AUC (95% CI) =0.811 (0.733–0.890), P<0.001], with 73.7% sensitivity and 77.0% specificity (Default 1). When this cut-off point was applied to the group of patients with indetermine SIT results, sensitivity was 71.4% and specificity 77.8%. Univariate and multivariate analyses indicated that a high A/K ratio increased the likelihood of a PA diagnosis, with an A/K ratio above 5.4 associated with a 4.585-fold higher risk (95% CI: 1.181–17.799, P=0.028) (Table 2).

Conclusion: The A/K ratio may predict PA. It offers advantages such as no need for pretest potassium or hospitalization, making it a useful supplementary parameter for diagnosing PA, particularly in patients for whom confirmatory tests are unsuitable.