A. ROC curves for visual diagnosis compared to log %HAA. For this quantitative method, mean AUC was 0.80 (range 0.79–0.81). B. ROC Curves for visual diagnosis compared to fibrosis scores. ROC analysis showed that fibrosis score discriminates subjects with visual diagnosis of PrePF. Average area under the curve (AUC) in five-fold cross validation was 0.92 (range 0.91–0.93) and average accuracy, sensitivity, and specificity in the test partitions were 0.85 (range 0.81–0.88), 0.81 (range 0.71–0.92), and 0.86 (range 0.79–0.90), respectively. Optimal threshold for log fibrosis score was 0.60 (range 0.53 – 0.71), corresponding to 1.8% fibrotic area in examined lung. (C) Density plots of fibrosis scores for visually diagnosed PrePF (pink) and No Fibrosis (blue) scans—the fibrosis score optimal threshold is indicated with the red line (0.60).