Biomarkers from bronchoalveolar lavage fluid in systemic sclerosis patients with interstitial lung disease relate to severity of lung fibrosis.

Objectives: Decision on treatment of systemic sclerosis (SSc) related interstitial lung disease (ILD) largely relies on the findings on high resolution computed tomography (HRCT) and there is a need for improvement in assessment of the fibrotic activity. The objectives of this study were to study biomarkers in bronchoalveolar lavage fluid (BALF) from SSc patients with ILD and to relate the findings to the severity and activity of lung fibrosis.

Methods: Fifteen patients with early SSc and 12 healthy controls were subjected to BAL. Cell counts and analyses of CXCL5, CXCL8 and S100A8/A9 were performed in BALF and serum. COMP and KL-6 were measured in serum. HRCT of lungs was quantified for ground glass opacities (GGO), reticulation and traction bronchiectases.

Results: BALF concentrations of CXCL8 (p < 0.001), CXCL5 (p = 0.002) and S100A8/A9 (p = 0.016) were higher in patients than controls. Serum KL-6 (p < 0.001) was increased in SSc patients and correlated with BALF concentration of eosinophils (rS = 0.57, p = 0.027). Patients with more widespread GGO on HRCT were characterised in BALF by a higher eosinophil count (p = 0.002) and in serum by higher KL-6 (p = 0.008). Patients with more fibrosis were characterised in BALF by higher eosinophil count (p = 0.014), higher CXCL8 (p = 0.005) and S100A8A/A9 (p = 0.014) concentration and in serum by a higher serum COMP (p = 0.023).

Conclusions: In SSc related ILD, biomarkers from BALF and serum correlate to findings on HRCT suggesting usefulness as markers of presence and extent of lung fibrosis.