The accuracy of IL-6, IL-8 and TNF-α for differentiating CTD-ILD from CTD-non-ILD was further evaluated by ROC analyses, and the AUCs were 0.63 (95% CI 0.51–0.75, P = 0.04), 0.64 (95% CI 0.52–0.76, P = 0.03) and 0.64 (95% CI 0.52–0.77, P = 0.02; Fig. 3a). Here, TNF is linked to interstitial lung disease.