[The Value of Serum Potassium and Ratio of Sodium to Potassium after Saline Infusion Test in Differential Diagnosis of Primary Hyperaldosteronism].

OBJECTIVE: To explore the electrolyte characteristics between different types of primary aldosteronism (PA), especially the value of serum potassium and the ratio of sodium to potassium after saline infusion test (SIT) in differential diagnosis of PA. METHODS: The clinical data was collected from 135 patients who received screening for the causes of hypertension from Jan. 2009 to Dec. 2018 in West China Hospital. The patients were divided into two groups: essential hypertension group (EH group, 34 patients) and primary aldosteronism group (PA group, 101 patients). PA patients were divided into aldosterone-producing adenoma group (APA group, 60 patients) and idiopathic hyperaldosteronism group (IHA group, 41 patients). To analyze the value of serum potassium and the ratio of sodium to potassium after SIT in the differential diagnosis of PA with receiver operating characteristic (ROC) curve. RESULTS: Compared with EH group, the serum potassium level of APA group was lower either before or after SIT ( P<0.01). The ratio of sodium to potassium before and after SIT in APA group were higher than that in EH group ( P<0.05). There were no differences between APA group and IHA group in the level of serum potassium and the ratio of sodium to potassium before SIT. The level of serum potassium after SIT in APA group was lower than that in IHA group ( P<0.01), and the ratio of sodium to potassium was higher ( P<0.05). The area under ROC curve ( AUC) of serum potassium level and the ratio of sodium to potassium after SIT were 0.641 and 0.646, respectively, while the AUC of aldosterone level was 0.788. The optimal cut-off value of serum sodium level was 3.56 mmol/L, with a sensitivity and specificity of 46.7% and 85.4%. The optimal cut-off value of ratio of sodium to potassium was 39.09, with 53.3% and 80.5% in sensitivity and specificity. CONCLUSION: The serum potassium and the ratio of sodium to potassium after SIT has limited diagnostic value for its low sensitivity in differential diagnosis of PA.

The number of positive confirmatory tests is associated with the clinical presentation and incidence of cardiovascular and cerebrovascular events in primary aldosteronism.

Primary aldosteronism (PA) is a major cause of secondary hypertension and presents a higher risk for cardio-cerebrovascular (CCV) events compared with essential hypertension. To diagnose PA after a positive screening test, at least one of three available confirmatory tests [the saline infusion test (SIT), the captopril challenge test (CCT) or the furosemide upright test (FUT)] should be performed. The aim of our study was to investigate the relationship between the number of positive confirmatory tests using SIT and CCT and the clinical presentation and prevalence of CCV events in 398 PA patients. The number of PA patients doubled when PA diagnosis was defined by positive results on either the SIT or CCT confirmatory tests (single positive) compared to positive results on both the SIT and CCT confirmatory tests (double positive). We also found a more typical clinical presentation of PA, such as the use of more antihypertensive drugs to control blood pressure and a higher incidence of hypokalemia, in PA patients with double positive confirmatory tests than in those with a single positive confirmatory test. The incidence of CCV events in PA patients with double positive confirmatory tests was significantly higher than that in those with a single positive confirmatory test. Our results demonstrated that the number of PA patients was doubled by the use of PA diagnostic criteria using a single positive confirmatory test compared to the use of double positive confirmatory tests. PA patients with double positive confirmatory tests were associated with a more typical clinical presentation and a higher incidence of CCV events than those with a single positive confirmatory test.