MON-207 Validating and Optimizing the Guideline Criterion for Skipping Confirmatory Tests of Primary Aldosteronism

Abstract Background: Confirmatory tests of primary aldosteronism (PA), including saline infusion test (SIT), captopril challenge test (CCT) and fludrocortisone suppression test (FST), are recommended by the Endocrine Society Clinical Practice Guideline. In order to simplifying diagnostic process, a criterion for skipping confirmatory tests was established by the guideline, while the evidence is lacking. Objective: To validate and optimize the guideline criterion for skipping confirmatory tests. Design: Prospective diagnostic study. Setting: Chongqing, China. Measurements: A total of 501 patients with high risk of PA were retrospectively enrolled. All of them completed at least two confirmatory tests (CCT, SIT, and FST). The guideline criterion is: history of spontaneous hypokalemia, plasma renin concentration (PRC) below detection levels and plasma aldosterone (PAC)>20ng/dl (550pmol/L). An optimized criterion (history of spontaneous hypokalemia, PRC <2.5 uIU/ml and PAC>20 ng/dl) was established based on the guideline criterion. Parameters such as sensitivity, specificity and area under the receiver-operator characteristic curves (AUC) were calculated to compare the diagnostic value of these two criteria. Results: Using SIT, CCT and FST (cutoffs: PAC post-SIT 10 ng·dl(-1); PAC post-CCT 11 ng·dl(-1); PAC post-FST 6 ng·dl(-1)) for PA diagnosis, the specificity of the guideline criterion was 1.00 (0.98–1.00), 1.00(0.98–1.00) and 1.00(0.97–1.00) respectively, while the sensitivity was 0.12 (0.09–0.17), 0.12(0.08–0.16) and 0.09(0.06–0.12) respectively. Compared to the guideline criterion, the sensitivity of the optimized criterion was significantly improved [SIT: 0.42 (0.36–0.49); CCT: 0.41 (0.35–0.48); FST: 0.30 (0.25–0.34), all the P values < 0.001 when compared to the guideline criterion]. However, the specificity of the optimized criterion was similar to the guideline criterion (all the P values>0.05). Limitation: This study was carried out in a single center. Conclusions: The guideline criterion shows high specificity but low sensitivity for direct diagnosis of PA. The optimized criterion has greatly improved the sensitivity and may be more suitable for skipping confirmatory tests of PA.