THU588 Sparing Confirmatory Testing In Primary Aldosteronism: The Combination Of Renin, Aldosterone And Potassium Levels

Disclosure: A.C. Ong Lopez: None. D.M. Dimayuga: None. L.E. Tiu: None. O.C. Dampil: None. E. Mendoza: None. M.L. Villa: None. A.M. Macabuag-Oliva: None. Background and Objective: The diagnosis of primary aldosteronism (PA) is comprehensive which includes case-detecting testing, case confirmation followed by subtype classification. In certain instances, one may not proceed with further confirmatory testing in the setting of spontaneous hypokalemia, suppressed renin, and PAC > 15 ng/dL. However, this quality of evidence is very low. This study sought to determine the optimal laboratory combination patterns that can spare confirmatory testing for primary aldosteronism by evaluating the diagnostic performances of the various combination settings and correlating to the recent evidence and clinical practice guidelines. Methodology: This is a multi-center, retrospective diagnostic accuracy cohort-selected cross-sectional study with a sampling total of 116 participants aged 18 years and above who underwent saline infusion test between January 2010 to March 2023. The main outcome measures comprise the diagnostic performances of the different index test combinations (baseline PAC, baseline PRA and presence of spontaneous hypokalemia) which include the sensitivity, specificity, negative predictive value, positive predictive value, positive likelihood ratio, negative likelihood ratio, and diagnostic accuracy. Data analysis was performed using SPSS 29.0.0.0 & MedCalc 20.218. Results: Of the 116 patients who underwent saline infusion test, 76 (65.52%) were diagnosed with PA. A PAC of > 25 ng/dL plus PRA < 1.0 ng/dL/hr with spontaneous hypokalemia showed the highest specificity at 100% (95% CI 89.11%, 100.00%) and positive predictive value at 100% (95% CI 82.35, 100.00%). The optimal combination criteria with the best balance of the diagnostic performance indices were determined to be a PAC of > 20 ng/dL plus PRA < 0.6 ng/dL/hr, and presence of spontaneous hypokalemia. It has a sensitivity of 34.72% (95% CI 23.88% , 46.86%), specificity of 93.75% (95% CI 79.19%, 99.23%), positive predictive value (PPV) of 92.59% (95% CI 75.71%, 99.09%), negative predictive value (NPV) of 38.96% (95% CI 28.05%, 50.75%), positive likelihood ratio (LR+) of 5.56 (95% CI 1.40, 22.06), negative likelihood ratio (LR-) of 0.70 (95% CI 0.58, 0.84), and a diagnostic accuracy of 52.88% (95% CI 42.85%, 62.75%). Conclusion: Hypertensive patients with spontaneous hypokalemia who had initial screening test results of PAC > 20 ng/dL and PRA < 0.6 ng/ml/hr can be diagnosed as overt primary aldosteronism and may not proceed with dynamic confirmatory testing. This is in line with the 2016 Endocrine Society Clinical Practice Guideline recommendation. Presentation: Thursday, June 15, 2023