Endocrine Abstracts

Introduction: Although the Endocrine Society guidelines recommend using aldosterone: renin ratio (ARR) to screen patients for primary aldosteronism (PA), whether to include a cut-off for aldosterone levels remains controversial. In Singapore, most centres require both an ARR >550 (ng/dl)/(ng/ml per h) and aldosterone ≥15 ng/dl. However, it has been shown that patients with PA may have aldosterone levels<15 ng/dl, and also respond well to mineralocorticoid antagonists. We examined the prevalence of Asian patients with high ARR, and influence of including patients with unsuppressed aldosterone levels >5 ng/dl.

Methods: We determined the prevalence of patients with high ARR >550 (aldosterone, ng/dl; plasma renin activity, ng/ml per hr) in a multi-ethnic Asian population with hypertension being screened for PA in a single tertiary centre, and stratified them by aldosterone levels.

Results: A total of 786 patients were screened for PA from 2015–2016, with 219 of 786 (27.8%) patients having a high ARR. Amongst these 219 patients with a high ARR, 68 of 219 (31.1%) had an aldosterone levels ≥15 ng/dl, 51 (23.3%) had aldosterone levels 10-14.9 ng/dl, 60 (27.4%) had an aldosterone levels 5–9.9 ng/dl, and 40 (18.3%) had aldosterone levels <5 ng/dl. When both ARR>550 and aldosterone ≥15 ng/dl are required, only 68 of 786 (8.6%) patients will proceed for confirmatory tests as per current practice. However, if all patients with ARR>550 and unsuppressed aldosterone levels ≥5 ng/dl are included, then 179 of 786 (22.8%) of patients should be considered for the diagnosis of PA.

Conclusion: Current practice of requiring a high aldosterone level in addition to a high ARR may underdiagnose patients with PA. However, potential benefit of working-up all patients with a high ARR has to be weighed against increased cost. A possible alternative would be a trial of mineralocorticoid therapy in these patients.