A subtype prediction score for primary aldosteronism

Abstract

Primary aldosteronism (PA) is the most common cause of endocrine hypertension. Although adrenal venous sampling (AVS) is recommended as the gold standard procedure for subtype classification in PA, it is a specialized technique with limited availability. The objective of this study was to develop a scoring system that predicted PA subtype using clinical characteristics. Seventy-one patients with PA were studied. The subjects were diagnosed as having either unilateral (n=32) or bilateral disease (n=39) based on AVS, surgery and/or the postoperative clinical course. Variables associated with laterality in the univariate analysis were entered into multivariable logistic regression models and the regression coefficients were used to construct a subtype prediction score. The diagnostic significance of the score was then evaluated using receiver operating characteristic (ROC) curve analysis. The subtype prediction score was calculated as follows: serum potassium ⩽3.4 mEq l(-1), 2 points; plasma aldosterone concentration ⩾165 pg ml(-1), 3 points; and aldosterone to renin ratio ⩾1000 in a post-captopril challenge test (plasma renin activity in ng ml(-1) h(-1)), 3 points. ROC curve analysis for the ability to discriminate between unilateral and bilateral PA showed that a score of 5 points had 75% sensitivity and 95% specificity, and a score of 3 points had a sensitivity of 97% and a specificity of 59%. The area under the ROC curve was 0.920 (95% confidence interval, 0.859-0.979). Our subtype prediction score could discriminate between unilateral and bilateral PA and is useful for selecting patients who should undergo AVS before surgery.