FRI158 Efficacy Of Oral Furosemide Test For Primary Aldosteronism Diagnosis

Disclosure: T. Castanheira de Freitas: None. A.W. Maciel: None. G.F. Fagundes: None. J. Petenuci: None. L. Santana: None. A. Guimaraes: None. F. Freitas-Castro: None. V. Srougi: None. F. Tanno: None. J. Chambo: None. M. Pereira: None. F. Coelho: None. L.P. Brito: None. A. Cavalcante: None. B. Pilan: None. F. Carnevale: None. A. Pio-Abreu: None. L. Bortolotto: None. A. Latronico: None. M.C. Fragoso: None. L. Drager: None. B.B. Mendonca: None. M.Q. Almeida: None. Background: 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. The most common tests are the saline infusion test (SIT), captopril chalenging test (CCT), fludrocortisone supression test (FST) and furosemide upright test (FUT). The sodium overloading tests are the most frequently used tests in clinical practice, but are not tolerated in patients with severe hypertension, hypervolemia and hypokalemia. The use of oral furosemide test as a new confirmatory test to simplify the confirmation of PA diagnosis was not investigated. Methods: We prospectively evaluated the diagnostic performance of oral 80 mg furosemide in 64 PA patients and in 22 with primary hypertension (controls). Direct renin concentration (DRC) was measured before, 2h and 3h after the oral furosemide. In addition, the oral furosemide test was compared with two other confirmatory tests: FUT and SIT or CCT in all PA patients. Results: The cut-off of 7.6 µU/mL for DRC at 2h after oral furosemide had a sensitivity of 92%, a specificity of 82% and an accuracy of 90% for PA diagnosis. The cut-off of 10 µU/mL at 2h had a higher sensitivity of 95.3%, but a lower specificity of 73%. In five out of six controls with low-renin hypertension, which might represent a PA spectrum, renin remained suppressed. Excluding these six controls with low-renin hypertension, the DRC cut-off of 10 µU/mL at 2h after oral furosemide had a sensitivity of 95.3%, a specificity of 93.7% and an accuracy of 95% for PA diagnosis. DRC after 3h 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%) PA patients. Only 4 out of 64 PA cases (6.4%) ended the oral furosemide test with potassium <3.5 mEq/L. Hypotension was not evidenced in any PA patient during the test. Conclusion: The oral furosemide test was safe, well-tolerated and represents an effective strategy for PA investigation.Support: Sao Paulo Research Foundation (FAPESP) grant 2019/15873-6 (to M.Q. Almeida) and by the Coordination of Superior Level Staff Improvement (CAPES) fellowship (to TCF). Presentation: Friday, June 16, 2023