Usefulness of the Upright Posture Test in the Diagnosis of Primary Aldosteronism.

Objective: To assess the usefulness of the upright posture stimulation test (UPT) in the confirmation of primary aldosteronism (PA) in patients in whom saline tests (ST) were inconclusive.

Methods: One hundred eighty-seven adult patients with possible PA were retrospectively included and compared to 25 control subjects. Blood samples were obtained after a 1-hour supine posture and during 2 hours of ambulation. An increase in plasma aldosterone concentration (PAC) ≥ 50% with a suppressed renin (≤10.1 ng/L; ≤1 ng/mL/hour) and a cortisol increase ≤50% were considered abnormal.

Results: PA patients had higher basal PAC and lower basal direct renin concentration (DRC) (P < .0001) and a higher maximal PAC (P = .0025) and lower maximal DRC (DRC_max) (P < .0001) during UPT compared to controls. PA was confirmed in 145 patients (77.5%), based on either oral/IV ST or UPT. DRC_max ≤12 ng/L during UPT was a predictor of PA (receiver operating characteristic curve sensitivity 93.8%, specificity 88%), and 95.6% of PA patients increased PAC ≥50% on UPT (median 222.2%), while renin remained suppressed. All 41 PA patients with false-negative IV ST (PAC < 162 pmol/L) and 88.9% with borderline response (162-240 pmol/L) had a DRC_max ≤12, while, respectively, 97.6% and 100% increased aldosterone by ≥50%. Similar responses to UPT were found in lateralized (28/63) and bilateral PA source (35/63). PA diagnosis increased from 23.6% to 88.8% using UPT results instead of IV ST and were confirmed at pathology and clinical outcome after adrenalectomy (n = 22).

Conclusion: UPT can be useful to confirm PA, particularly in patients with suspected false-negative ST.