The serum sodium to urinary sodium to (serum potassium)2 to urinary potassium (SUSPPUP) ratio in patients with primary aldosteronism

Background  The aldosterone-to-renin ratio (ARR) is an established diagnostic tool in the screening for primary aldosteronism (PA). However, hormonal determinations are time consuming and expensive. Therefore, we studied the effectiveness of the serum sodium to urinary sodium to (serum potassium)² to urinary potassium (SUSPPUP) ratio in the diagnosis of PA.
Design  This study included 35 patients with PA, 71 patients with essential hypertension to whom this diagnosis could be excluded, 23 normal subjects without hypertension, and 22 patients with primary adrenal insufficiency. We compared the SUSPPUP ratios with the ARR in these patient groups.
Results  We show that the ARR distinguished PA from essential hypertension with a sensitivity of 94·2% and a specificity of 92·1% at a cutoff of 33 (ng L⁻¹: ng L⁻¹). It correlated well with the SUSPPUP ratio. The sensitivity and specificity of SUSPPUP was 88·6% and 85·9% at a cutoff of 5.3 (mmol L⁻¹)⁻¹, respectively, and thus not as good as the ARR.
Conclusions  The ARR is a good parameter in the screening for PA. The SUSPPUP ratio is a cheap and rapid tool to assess the extent of mineralocorticoid excess and, therefore, can be offered to more patients. In addition, the application of the SUSPPUP ratio can be extended to patients who suffer from other forms of mineralocorticoid hypertension (e.g. with low aldosterone levels).