How do I interpret the results of the aldosterone-to-renin ratio in the context of diagnosing primary aldosteronism?

Interpretation of the aldosterone-to-renin ratio (ARR) in diagnosing primary aldosteronism (PA) requires understanding that a raised ARR is a sensitive screening indicator suggestive of PA, but must be interpreted in the clinical context and alongside confirmatory testing.

A high ARR reflects inappropriately elevated aldosterone relative to suppressed renin, which is characteristic of PA due to autonomous aldosterone secretion NICE NG203. However, the absolute aldosterone and renin values, patient posture, medications, and potassium status can influence the ratio and must be considered to avoid false positives or negatives Li et al. 2016Schilbach et al. 2019.

UK guidelines recommend using the ARR as an initial screening tool in patients with hypertension and hypokalaemia or resistant hypertension, but emphasise that a raised ARR alone does not confirm PA; it necessitates confirmatory testing such as saline infusion or fludrocortisone suppression tests NICE NG203.

Recent meta-analyses and studies support the ARR’s high sensitivity but variable specificity, highlighting the importance of standardised sampling conditions and interpretation thresholds tailored to the assay used Hung et al. 2021Li et al. 2016. They also note that direct renin concentration or plasma renin activity can be used, but results are not interchangeable and require assay-specific cut-offs Schilbach et al. 2019.

In summary, a raised ARR should prompt further confirmatory testing rather than be used in isolation to diagnose PA. Interpretation must integrate clinical features, biochemical context, and assay-specific reference ranges to optimise diagnostic accuracy NICE NG203 Hung et al. 2021Schilbach et al. 2019.