The present study was undertaken prospectively to compare the diagnostic significance of the seated saline suppression testing (SSST) with the captopril challenge testing (CCT) in hypertensive patients with suspected primary aldosteronism (PA) using the fludrocortisone suppression testing (FST) as the reference standard, and to investigate the optimal cutoff of SSST for differentiating PA from other forms of hypertension.

The diagnosis of primary aldosteronism (PA) typically requires at least one confirmatory test. Four tests are commonly recommended by the Endocrine Society guideline, namely, oral sodium loading, saline infusion, fludrocortisone administration with oral sodium loading, and captopril challenge testing (CCT). Of these, fludrocortisone suppression testing (FST) has been considered the most reliable, but is cumbersome, difficult to perform, and relatively expensive, requiring hospital admission for several days. Alternative approaches to FST have included saline suppression testing (SST), Which requiring patients staying in the recumbent position for at least 1 h before and during the infusion of 2 L of 0.9% saline IV over 4 h. This approach also has the disadvantages of brings much inconvenience to the patient (such as urination or defecation, etc.). Ashraf H. et al. have reported that seated SST (SSST) is more sensitive than recumbent SST (RSST), especially for posture-responsive PA (95.8% versus 33.3%), however, in this small scale study, only 31 patients was PA and only three patients was tested negative for PA by FST. Specificity of each form of SST was unable to estimate and meaningful receiver operating characteristic (ROC) curve analyses could not be performed. Furthermore, it is lack of study in Chinese people. In addition, the investigators have previously found the CCT was as accurate as the FST and plasma aldosterone concentration (PAC) post-CCT is the best approach to interpret the results of the CCT. The present study was undertaken prospectively to compare the diagnostic significance of the SSST with the CCT in hypertensive patients with suspected PA using the FST as the reference standard, and to investigate the optimal cutoff of SSST for differentiating PA from other forms of hypertension.

Inclusion Criteria:

1. patients with Joint National Commission stage 2 (>160-179/100-109mm Hg), stage 3 (>180/110 mmHg), or drug-resistant hypertension;
2. hypertension and spontaneous or diuretic-induced hypokalemia;
3. hypertension with adrenal incidentaloma;
4. hypertension and a family history of early-onset hypertension;
5. cerebrovascular accident at a young age (<40 years);
6. all hypertensive first-degree relatives of patients with PA.

Exclusion Criteria:

1. heart failure;
2. chronic kidney disease with an estimated Glomerular Filtration Rate <30 ml/min/1.73 m2;
3. liver cirrhosis;
4. terminal malignant tumor;
5. current use of steroids or oral contraceptives;
6. pregnancy or lactation.

Hospital or clinic patients with hypertension in a single tertiary hospital center.