Serum MMP-9, SP-D, and VEGF levels reflect the severity of connective tissue disease-associated interstitial lung diseases

Key points Serum MMP-9, SP-D, and VEGF levels were increased in patients with CTD-ILD and they may have clinical value in screening and evaluating the severity of CTD-ILD. Serum SP-D and VEGF levels had a positive correlation with ILD severity as measured using semiquantitative HRCT scores. Serum MMP-9 levels were elevated in the UIP subgroup compared to the non-UIP subgroup. Therefore, further research is required to determine the role of serum MMP-9 levels in the preliminary determination of the ILD subtype. Serum MMP-9 levels had a negative correlation with DLco, and serum SP-D levels had a negative correlation with FVC.