Fig 3. Receiver operating characteristic (ROC) curve of uric acid stones for mean stone density and stone heterogeneity index.

(A) The area under the ROC curve (AUC) for the mean stone density was 0.766 (95% confidence interval [CI], 0.696–0.836) and the cut-off value was 572.3 HU. (B) The AUC for the stone heterogeneity index was 0.885 (95% CI, 0.824–0.945) and the cut-off value was 140.4 HU.