SUN-366 The Optimal Cutoff Value for Basal Plasma Aldosterone Concentration Suspected as Primary Aldosteronism Distributed According to Aldosterone-Renin Ratio and Confirmatory Tests Response

Aldosterone/renin ratio (ARR) >200 [(pg/mL)/(ng/mL/hr)] is a widely accepted threshold to screen for primary aldosteronism (PA) (1). Because using ARR as a sole index leads to excessive inclusion of cases with low renin essential hypertension, it may be desirable to combine ARR with a minimum plasma aldosterone concentration (PAC) value to increase diagnostic accuracy, but currently there is no consensus on the minimum PAC value. Therefore, we carried out a single-center, retrospective study to investigate optimal PAC cutoff to be used with ARR >200. The subjects were 385 individuals (240 female and 145 male) with ARR >200 who underwent PA screening tests between 2010 and 2015. They were diagnosed according to the Japan Endocrine Society guideline (2) with either PA or essential hypertension (EH). The optimal cutoff value for baseline PAC that best distinguished between PA and EH was calculated. Of the 385 subjects, 297 were diagnosed with PA and 88 with EH. Of 194 PA patients who underwent adrenal venous sampling, 141 exhibited aldosterone hypersecretion from both adrenal glands, and 53 were diagnosed with aldosterone-producing adenoma (APA) on the basis of adrenalectomy. There was no difference between the PA (n = 194) and EH (n = 88) groups in terms of age, body mass index, or glucose and lipid profiles. Receiver operating characteristic curve analysis found that the optimal baseline PAC for distinguishing between PA and EH was 171 pg/mL, which provided a sensitivity of 0.75 and a specificity of 0.65 (area under the curve 0.718 and 95% confidence interval 0.656-0.780). Baseline PAC was ≥171 pg/mL for all 53 subjects with APA (minimum 171 pg/mL, maximum 943 pg/mL, and median 341 pg/mL), and if the cutoff value for baseline PAC is set at 171 pg/mL, it is unlikely that significant cases of APA will be overlooked in PA screening using ARR >200. Combining PAC ≥171 pg/mL with ARR >200 increases diagnostic accuracy for PA without compromising APA detection. Reference: (1)Hiramatsu et al., Arch Intern Med. 1981 Nov;141(12):1589-93. (2) Nishikawa et al., Endocr J. 2011;58(9):711-21.