Specifically, we confirmed the capacity of MMP-3, MMP-9, and TIMP-1 serum levels to differentiate between RA-ILD+ and IPF patients (AUC: 0.6504, p = 0.0166; AUC: 07292, p = 0.0003; and AUC: 0.6949, p = 0.0018, respectively, Fig. 6A, Additional File 2: Table S2). This evidence concerns the gene MMP9 and rheumatoid arthritis.