Risk factors for lung function decline in systemic sclerosis-associated interstitial lung disease in a large single-centre cohort

Objectives The aim of this study was to identify risk factors of percent predicted forced vital capacity (ppFVC) decline in patients with SSc-associated interstitial lung disease (SSc-ILD). Methods We identified 484 patients with SSc who had HRCT Chest, of which 312 with ILD. Those with serial pulmonary function tests were included in a longitudinal analysis (n = 184). Linear mixed effect models were fitted to assess the decline in ppFVC over time, and to explore the effect of demographics and baseline characteristics on ppFVC decline. Results The majority of SSc-ILD patients were female (76.3%) and 51.3% had diffuse cutaneous subset. The mean (s.d.) age was 53.6 (12.7) years, median disease duration since first non-RP symptoms was 2.6 years, and 48.4% of the patients had ILD extent >20% on HRCT. In the univariate analysis, longer disease duration (>2.37 years), ILD extent >20%, and anti-topoisomerase I (ATA) positivity were significantly associated with ppFVC decline. In the multivariate analysis, the only statistically significant variable associated with ppFVC decline was ATA positivity. The overall group's mean decline in ppFVC was -0.28% (P-value 0.029), with -0.13% (n = 163) in those who were alive and -8.28% (P-value 0.0002 for the change in ppFVC trajectory) in patients who died within 2 years. Conclusion Our study confirms that ppFVC is a marker of survival in SSc-ILD, supporting its use for risk stratification to identify patients who may benefit from earlier interventions and treatment. Our study also supports the role of ATA positivity as a predictive marker for ppFVC decline in this population.