Analysis of predictors of lung function decline in patients with systemic sclerosis associated ILD (SSc-ILD): data from the German Network for Systemic Sclerosis.

<bold>Background:</bold> The lung function decline in patients with systemic sclerosis SSc-ILD seems to be highly variable and is poorly understood. The study was aimed at identifying predictors of decline in FVC and DLco in patients with SSc-ILD. <bold>Patients and methods:</bold> Clinical data of 6,234 patients with SSc were collected in the German Network for Systemic Sclerosis registry. Disease progression was defined as ≥ 10% relative decline in FVC% pred. or ≥ 5 to < 10% decline in relative FVC pred. and 15% relative decline in DLCO% pred. from baseline. Change in FVC and DLco was analyzed using a mixed model for repeated measures (MMRM) with random imputation of missing data. Cox proportional hazards regression analysis was used to investigate predictors of lung function decline. <bold>Results:</bold> 1313 patients with SSc-ILD were included in the analysis. Mean follow-up time was 3.99 ± 1.79 years and 246 (19%) patients had ILD progression. Mean time to progression was 2.84 ± 1.72 years. The average rate of decline in FVC % pred. was 7.33% per year in patients with ILD progression with a difference of 16.91% to non-progressors (p=<0.001). The average rate of decline in DLco% pred. was 9.16% per year in patients with a difference of 12.09% to non-progressors (p= <0.001). Anti scl-70 and RNA polymerase III antibodies were the strongest predictors of ILD progression at Cox regression analysis (HR 1.916, CI: 1.002-3.955 and HR 2.898, CI: 1.370-4.739, p<0.001 and p=0.004, respectively). <bold>Conclusion:</bold> Disease progression in SSc-ILD patients seems to occur within the first 5 years after ILD diagnosis and to be strongly associated with autoantibody status.