P136 KL6 and IL-18 levels are negatively correlated with respiratory function tests and interstitial lung disease extent assessed on high-resolution computed tomography in patients with systemic sclerosis-related interstitial lung disease

Abstract

Abstract Background/Aims Serum biomarkers have been suggested as indicators for pulmonary damage with clinical value in the diagnosis and prognosis of SSc-ILD. We aim to investigate the role of serum biomarkers (Krebs von den Lungen-6 KL-6, IL-18 and IL- 18BP) as potential biomarkers reflecting the severity of SSc-ILD as assessed through high-resolution computed tomography (HRCT) and pulmonary function tests (PFT). Methods A cross-sectional study including patients with SSc fulfilling the 2013 ACR/EULAR criteria was performed. Patients were classified according to disease duration and pulmonary involvement. All SSc patients underwent chest HRCT scans and pulmonary function test at baseline. Serum concentration of KL-6, IL8 and IL18BP were determined usingsandwich ELISA technique (solid phase sandwich Enzyme Linked-Immunosorbent Assay), with kits from MyBiosource for KL-6 and from Invitrogen for IL18 and IL18BP. A semiquantitative grade of ILD extent was evaluated through HRCT scan (grade 1, 0-20%; grade 2, >20%). Extensive lung disease was defined as > 20% of lung involvement on HRCT, and FVC <70% predicted and limited lung involvement as ≤ 20% of ILD involvement on HRCT,and an FVC ≥70% predicted. Results 74 patients were included, 27% were male, with a mean age of 57.5±15 years. 28 patients had ILD (38%). 64 % of patients had <20% of ILD extent classified through HRCT scan. SSc-ILD patients had elevated serum KL- 6 and IL-18 levels compared to patients without ILD (p = 0.003 and p = 0.04). A negative correlation between KL-6 levels and %FVC (β=-0.25, p 0.037) and %DLCO (β=-0.28, p 0.02) and between IL-18 levels and %FVC (β=-0.20, p 0.03) and %DLCO (β=-0.14, p 0.04) were found. Serum KL-6 and IL-18 levels successfully differentiated grades I and II (p = 0.028 and p = 0.021). Semiquantitative grades of ILD on the HRCT scan were significantly proportional to the KL-6 (p 0.01) and IL-18 (p = 0.03). A positive correlation between extensive lung disease and KL-6 (β = 0.61, p 0.007) but not with IL-18 was found. Conclusion Serum KL-6 levels and IL-18 were increased in patients with SSc-ILD and showed a positive correlation with ILD severity as measured using a semiquantitative HRCT grading scale and a negative correlation with PFT parameters. Disclosure C. Sieiro Santos: None. S. Calleja Antolín: None. J. de la Calle Lorenzo: None. E. Bollo de Miguel: None. E. Díez Álvarez: None.