MUC1 and interstitial lung disease: The LR model based on the three biomarkers exhibited markedly better diagnostic performance (AUC = 0.880, 95%CI = 0.834–0.925) in serum-KL-6-negative ILD, than the conventional serum-KL-6-based method and could also accurately diagnose connective tissue disease associated-ILD (CTD-ILD) in the context of CTD.