[New index of using serum sodium and potassium and urine sodium and potassium jointly in screening primary aldosteronism in hypertensive patients].

Objective: Although the aldosterone-to-renin ratio (ARR) is valuable in the screening for primary aldosteronism (PA). However, the hormonal determinations are both time-consuming and expensive. So we tried to use new indexes of serum sodium to urinary sodium to serum potassium to urinary potassium (SUSPUP) and serum sodium to urinary sodium to (serum potassium)2 to urinary potassium (SUSPPUP) in screening of PA.

Methods: The present study included 39 patients with PA, 296 patients with essential hypertension and 158 normosensitive subjects. Serum potassium and sodium, urine potassium and sodium were measured by ion-selective electrodes. In addition, serum aldosterone concentration and plasma rennin activity after staying upright for one hour were measured by radioimmunoassay. The serum potassium and sodium, urine potassium and sodium in these groups were evaluated in the screening of SUSPPUP for differentiating PA from hypertensive patients.

Results: (1) Compared with healthy volunteers, the essential hypertension patients had lower levels of both serum potassium and urine sodium, higher levels of serum sodium. Compared with healthy volunteers and primary hypertension patients, the PA patients had the lowest serum potassium and highest serum sodium, urine potassium resulting in the highest SUSPUP and SUSPPUP ratio. (2) The AUCs of SUSPUP and SUSPPUP were 0.824 and 0.840 respectively according to the ROC curve. The optimal cutoffs of SUSPUP and SUSPPUP were 14.44 and 4.08 respectively.

Conclusion: The SUSPUP and SUSPPUP ratios are rapid and inexpensive indices to assess the extent of mineralocorticoid excess. Therefore they may be employed to screen PA in hypertensive patients.