Subsequently, the LR model analysis results (AUC = 0.798, 95%CI 0.690–0.910) showed that this biomarker combination differentiated between CTD-ILD and CTD in serum-KL-6-negative patients more effectively than serum KL-6 and the three individual exosomal biomarkers (Fig. 4B). Here, MUC1 is linked to interstitial lung disease.