MUC5AC and interstitial lung disease: Median MUC5AC levels were 1.30 ng/mL (IQR, 0.75 to 1.63 ng/mL) in the healthy controls, 0.84 ng/mL (IQR, 0.56 to 1.34 ng/mL) in the CTD-non ILD group, and 1.80 ng/mL (IQR, 1.13 to 2.60 ng/mL) in the CTD-ILD group.