Predictors for progressive fibrosis in patients with connective tissue disease associated interstitial lung diseases

Background: Connective tissue disease associated interstitial lung disease (CTD-ILD) is associated with decreased quality of life and high mortality risk. Outcome and treatment response is unpredictable. This study aimed to identify clinical predictors for CTD-ILD with poor outcome. Methods: We performed a retrospective single centre cohort study in outpatients with CTD-ILD seen between 2004 and 2018. Clinical and biochemical data, pulmonary function tests (PFT) and high-resolution computed tomography (HRCT) results were analysed. Overall survival and progressive fibrosing ILD (PF-ILD, defined as a significant deterioration of PFT or HRCT) after two years of follow-up were assessed. Results: In total, 150 patients with CTD-ILD were included. Thirty (20%) deaths occurred during a median follow-up of 40 months (IQR 27.3–60.8), which were attributed to pulmonary infection in six (4%), respiratory failure due to PF-ILD in ten (7%) and due to other causes in fourteen patients. PF-ILD occurred in 76 (50.7%) patients and was associated with poor overall survival (adjusted HR 5.73, 95%CI 1.17–28.11). Age, smoking, C-reactive protein, and steroid-use were independently associated with increased mortality risk as well. Furthermore, patients with diabetes mellitus (adjusted OR 4.52, 95%CI 1.10–18.51), steroid-use (adjusted OR 2.26, 95%CI 1.04–4.93), and a fibrotic HRCT pattern at baseline (adjusted OR 3.11, 95%CI 1.15–8.38) had a higher risk of PF-ILD. Conclusion: PF-ILD is associated with increased mortality in patients with CTD-ILD. Patients with a fibrotic HRCT pattern at baseline, diabetes mellitus and steroid-use have a higher risk of developing PF-ILD.