Efficacy of Oral Furosemide Test for Primary Aldosteronism Diagnosis

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 (DRCmax) (P < .0001) during UPT compared to controls. PA was confirmed in 145 patients (77.5%), based on either oral/IV ST or UPT. DRCmax ≤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 DRCmax ≤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.

Renal Function Evolution and Hypoaldosteronism Risk After Unilateral Adrenalectomy for Primary Aldosteronism

Few studies demonstrated a percentage decrease in the estimated glomerular filtration rate (eGFR) at a single time and the rate of hypoaldosteronism after adrenalectomy for primary aldosteronism (PA). Our aim was to investigate the evolution of renal function and the hypoaldosteronism risk after adrenalectomy for PA. Aldosterone, renin, eGFR, and electrolyte levels were determined before and at 1 week, 1, 3 and 6 months after unilateral adrenalectomy in 94 PA patients (40 men and 54 women). The main outcome was the postoperative eGFR decline using analysis of covariance with the preoperative eGFR as a covariate. eGFR decreased during first postoperative week compared to 3 months before surgery. During the first 6 months, eGFR remained stable at similar levels to the first week after surgery. Age (p=0.001), aldosterone levels (p=0.021) and eGFR 3 months before surgery (p+<+0.0001) had a significant correlation with eGFR during first postoperative week. High aldosterone levels at diagnosis were correlated with decline in renal function in the univariate model (p=0.033). In the multivariate analysis, aldosterone levels at diagnosis had a tendency to be an independent predictor of renal function after surgery (p=0.059). Postoperative biochemical hypoaldosteronism was diagnosed in 48% of the cases after adrenalectomy, but prolonged hyperkalemia occurred in only 4 cases (4.5%). Our findings showed a decrease of eGFR after unilateral adrenalectomy for PA. Additionally, aldosterone levels at diagnosis correlated with postoperative renal function. Postoperative biochemical hypoaldosteronism occurred in almost half of the patients, but prolonged hyperkalemia with fludrocortisone replacement was less frequent.

Efficacy of Oral Furosemide Test for Primary Aldosteronism Diagnosis

Context

Confirmatory tests represent a fundamental step in primary aldosteronism (PA) diagnosis, but they are laborious and often require a hospital environment due to the risks involved.

Objective

To evaluate the efficacy of oral furosemide as a new confirmatory test for PA diagnosis.

Methods

We prospectively evaluated the diagnostic performance of 80 mg of oral furosemide in 64 patients with PA and 22 with primary hypertension (controls). Direct renin concentration (DRC) was measured before, and 2 hours and 3 hours after the oral furosemide. In addition, the oral furosemide test was compared with 2 other confirmatory tests: the furosemide upright test (FUT) and saline infusion test (SIT) or captopril challenge test (CCT) in all patients with PA.

Results

The cut-off of 7.6 µU/mL for DRC at 2 hours after oral furosemide had a sensitivity of 92%, specificity of 82%, and accuracy of 90% for PA diagnosis. In 5 out of 6 controls with low-renin hypertension, which might represent a PA spectrum, renin remained suppressed. Excluding these 6 controls with low-renin hypertension, the DRC cut-off of 10 µU/mL at 2 hours after oral furosemide had a sensitivity of 95.3%, specificity of 93.7% and accuracy of 95% for PA diagnosis. DRC after 3 hours of oral furosemide did not improve diagnostic performance. Using the cut-off of 10 µU/mL, the oral furosemide test and the FUT were concordant in 62 out of 64 (97%) patients with PA. Only 4 out of 64 cases with PA (6.4%) ended the oral furosemide test with potassium <3.5 mEq/L. Hypotension was not evidenced in any patient with PA during the test.

Conclusion

The oral furosemide test was safe, well-tolerated and represents an effective strategy for PA investigation.