The clinical value of urinary potassium to serum potassium square ratio and supine-to-standing test for screening primary aldosteronism and subtype diagnosis in patients with hypertension

Objective To investigate the clinical value of urinary potassium to serum potassium square ratio (UPPP) and supine-to-standing test for screening primary aldosteronism (PA) and distinguishing PA subtype in patients with hypertension.

Methods This study was a retrospective analysis. The clinical data of 60 patients with primary aldosteronism (PA) (PA group) and 60 age, gender and body mass index-matched patients with essential hypertension (EH) from Henan Provincial People's Hospital from January 2020 to August 2023 were collected. PA was diagnosed by intravenous saline stress test (ISLT). The clinical data, urine potassium to blood potassium ratio (UPP) and UPPP were compared between the two groups. The correlations between UPP, UPPP and plasma aldosterone to renin activity ratio (ARR) in supine and standing positions were analyzed. Receiver operating characteristic (ROC) curve was used to evaluate the efficacy of ARR, UPP and UPPP in supine and upright positions in screening PA and the clinical value of supine and upright position test in the subtype diagnosis of PA.

Results  The levels of serum sodium, 24 h urinary potassium, UPP, UPPP, supine PAC, supine ARR, upright PAC and upright ARR in PA group were higher than those in EH group (all P＜0.05). The serum potassium and PRA in supine and upright in PA group were lower than those in EH group (P＜0.05). UPPP was highly correlated with supine or upright ARR (r_s=0.980, 0.905, all P＜0.001). The efficiency of supine ARR (AUC:0.989) for screening PA was similar to that of upright ARR (AUC:0.991) (Z=0.643, P=0.520). The efficiency of UPPP (AUC: 0.938) for screening PA was lower than that of supine ARR (AUC:0.989) and upright ARR (AUC:0.991) (Z=2.841, 2.816; P=0.005, 0.005). The efficiency of UPPP was higher than that of UPP (AUC: 0.881) (Z=4.185, P＜0.001). The sensitivity of UPPP for screening PA was 91.67%, and the specificity was 90.00%. The diagnostic rate of aldosterone- producing adenoma (APA) was 100% when the percentage of PAC increase in the supine position test was ≤ 30%, while patients with a PAC increase percentage greater than 30% cannot be definitively diagnosed with idiopathic aldosteronism.

Conclusions The value of supine ARR and upright ARR for screening PA is equivalent; UPPP is highly correlated with supine and upright ARR. The screening value of UPPP is slightly lower than that of supine and upright ARR, and better than that of UPP, it has higher sensitivity and specificity. PAC increase percentage ≤30% in the supine position test has a certain value for the diagnosis of APA.