Sodium Infusion Test for Diagnosis of Primary Aldosteronism in Chinese Population

CONTEXT: The plasma aldosterone concentration (PAC) is less than 5 ng/dL after saline infusion test (SIT) in essential hypertension (EH) and healthy people. It is unclear if the same standard is applicable for Chinese subjects. OBJECTIVE AND DESIGN: We assessed the serum aldosterone response after SIT in subjects with primary aldosteronism (PA), EH, and healthy volunteers (normal control, NC), and to investigate the optimal aldosterone level of post-SIT for the diagnosis of PA. SUBJECTS AND SETTING: The study included 120 hypertensive patients who conform to the PA screening criteria and 21 healthy volunteers. INTERVENTION: All subjects underwent SIT. MAIN OUTCOME MEASURES: PAC was measured in all subjects before and after SIT. The total sodium intake was estimated from 2 timed 24-hour urinary excretion. RESULTS: The area under the receiver-operator characteristic curves was higher than under the diagonal (0.967, 95% confidence interval [CI]: 0.94-0.993). The best cutoff value for PAC after SIT for diagnosis of PA was 11.45 ng/dL, with sensitivity and specificity of 88.2% and 95.4%, respectively. The PAC of post-SIT was more than 10 ng/dL in most PA patients, whereas it was greater than 5 ng/dL in both EH and NC except for 1 at 4.93 ng/dL. Serum aldosterone level was unrelated to dietary salt intake. CONCLUSIONS: The optimal post-SIT aldosterone cutoff value for identifying PA was 11.45 ng/dL in Chinese patients. However, the PAC higher than 5 ng/dL after SIT was found in a majority of EH and healthy subjects. The cutoff value of aldosterone post-SIT is higher than the current clinical recommendations and practice guidelines of The Endocrine Society. We found no relationship between high salt intake and lower responses of renin aldosterone system to high loading with saline infusion.