Background/Purpose Rheumatoid arthritis (RA) is the most common systemic connective tissue disease in the U.S. Interstitial lung disease (ILD) is a frequent extra-articular manifestation of RA that contributes significantly to morbidity and mortality. While risk factors for developing ILD have been identified, less is known about factors that predict prognosis. The objectives of this study were to identify factors associated with RA-ILD progression and determine how often RA-ILD pulmonary activity parallels joint disease activity.

Methods We performed a retrospective analysis of adult patients with RA-ILD at the University of Chicago Medical Center. Demographic and clinical information were extracted from medical records. All patients met ACR 1987 classification criteria for RA. ILD diagnosis required interstitial abnormalities on high-resolution chest CT plus confirmation by a pulmonologist, with or without restrictive pattern on pulmonary function tests (PFTs) or compatible lung biopsy. Progressive RA-ILD was defined as decrease in forced vital capacity of ≥10% or diffusing capacity for carbon monoxide of ≥15% on serial PFTs ≥8 weeks apart. Progressive joint disease was defined as evidence of new erosion or persistent flare by rheumatologist on successive visits ≥8 weeks apart. Patients with parallel ILD and joint activity had worsening in PFTs and joint disease activity within 3 month overlapping period. Subgroups of patients were compared using Fisher’s exact tests for categorical variables and ANOVA for continuous variables.

Results We identified 47 RA-ILD patients. Thirty six (77%) had progressive RA-ILD and 11 (23%) had stable RA-ILD. High-titer rheumatoid factor (RF), >3 times upper limit of normal, was associated with progressive RA-ILD (p=0.0394) while high-titer cyclic citrullinated peptide (CCP) antibody (p=0.0973) and smoking history (p=0.0933) trended towards association. Twenty eight patients had serial rheumatology assessments coinciding with PFTs: 9 (32%) had parallel ILD and joint disease activity, and 19 (68%) had non-parallel disease activity. Usual interstitial pneumonia (UIP) was the most common radiographic pattern in patients with progressive and stable RA-ILD. There was a slight predominance of UIP as the radiographic pattern in patients with non-parallel ILD and joint disease activity. Radiographic patterns other than pure UIP were slightly more frequent in patients with parallel ILD and joint disease activity.

Conclusion High-titer RF was associated with RA-ILD progression in this cohort. High-titer CCP antibody and smoking history trended towards association with progressive RA-ILD. Thus, we propose that RA-ILD patients with these risk factors merit closer monitoring for disease progression. For the majority of our RA-ILD cohort, ILD and joint disease activity did not parallel one another. This finding highlights the importance of monitoring joint and lung disease separately, as different factors may contribute to articular and pulmonary disease flares in RA-ILD patients. Furthermore, these results suggest that articular and pulmonary disease activity should be considered separately for therapeutic decision-making.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rheumatoid-arthritis-associated-interstitial-lung-disease-risk-factors-for-disease-progression/