According to the receiver operating characteristic (ROC) curve analysis, all three biomarkers exhibited excellent performance (area under the ROC curve [AUC] for KL-6: 0.945, 95% confidence interval [CI] 0.910–0.979; CAPN2: 0.948, 95% CI 0.915–0.981; SP-B: 0.838, 95% CI 0.778–0.898) in distinguishing the ILD group from the two control groups. Here, CAPN2 is linked to interstitial lung disease.