Oral Sodium Loading Test Is More Sensitive Than Seated Saline Infusion Test to Confirm Overt Primary Aldosteronism

Primary aldosteronism (PA), a frequent but underdiagnosed cause of hypertension, is associated with a significant burden of cardiovascular and renal complications. Studies have reported divergent results regarding the diagnostic performance of seated saline infusion test (SSIT) and oral sodium loading test (OSLT), 2 confirmatory tests recommended by the Endocrine Society Clinical Practice Guidelines. To our knowledge, no study directly compared the results of SSIT and OSLT to diagnose overt PA.

We assessed the diagnostic performance of SSIT and OSLT in a group of patients with hypertension and elevated screening aldosterone-renin ratio (ARR). The diagnostic standard was defined as hypertension with or without hypokalemia with an elevated screening ARR and at least 1 abnormal confirmation test including OSLT and SSIT.

A monocentric retrospective study was conducted, including 87 patients with hypertension with a positive screening who underwent both SSIT and OSLT. A diagnostic performance analysis was conducted using urinary aldosterone at a threshold of 27 nmol/day as the criterion for OSLT, in comparison to a plasma aldosterone concentration (PAC) exceeding 140 pmol/L following the saline infusion.

A statistically significant difference in sensitivity was observed between OSLT and SSIT, with OSLT demonstrating superior performance (P = .025). The aforementioned test exhibited concordance in 59 cases (65.5%), indicating that these methods are not equivalent (McNemar test P = .036).

OSLT demonstrated a significantly higher sensitivity for diagnosing overt PA in comparison with the SSIT in our cohort of patients with hypertension with an abnormal screening ARR.