In the past decade, lung ultrasound (LUS) B-lines and serum Krebs von den Lungen-6 (KL-6) antigen have been recognized as biomarkers of the connective tissue disease-associated interstitial lung diseases (CTD-ILDs).
The median serum KL-6 level was 1450.5 U/mL (interquartile range (IQR) 742.9-2603.2) in the CTD with ILD group, 415.9 U/mL (IQR 233.4-748.4) in the CTD without ILD group, and 465.9 U/mL (IQR 273.6-1036) in the control group.