PRTN3 and chronic lung disease: The area under the curve (AUC) values of the ROC curves with 95% confidence intervals and the optimized cut-off levels with specificities and sensitivities are shown: MDA5: melanoma differentiation-associated gene 5, Ab: antibody, RF: rheumatoid factor, ACPA: anti-cyclic citrullinated peptide antibody, ROC: receiver operating characteristic, AUC: area under the curve, and CLD: chronic lung disease.