Of 66 patients who underwent FST ( upright plasma aldosterone levels measured at 10am basally and after 4 days fludrocortisone 0.1 mg 6-hourly and oral salt loading ) , 31 underwent SST ( aldosterone levels measured basally at 8am and after infusion of 2 L normal saline over 4h ) both recumbent and seated in randomized order and at least 2 weeks apart .