Functional, radiological and survival outcomes in rheumatoid arthritis-associated interstitial lung disease: 24-month results from the BERTHA prospective cohort

Background Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is heterogeneous. Forced vital capacity (FVC) decline and high-resolution CT (HRCT) pattern are widely used as prognostic markers, but the natural history of RA-ILD identified in rheumatology clinics, particularly in mild disease, remains insufficiently described. Methods We conducted a prospective, multicentre cohort study across three Brazilian centres. Adults with RA-ILD were followed every 6 months for 24 months. Pulmonary function tests, HRCT, 6 min walk test and King’s Brief Interstitial Lung Disease health-related quality-of-life questionnaire were performed at baseline, 12 and 24 months. Blood biomarkers were assessed at baseline, 6 and 18 months. HRCT scans were independently reviewed by two chest radiologists and analysed using densitometry-based quantitative CT (QCT). Pulmonary fibrosis was qualitatively defined by unequivocal traction bronchiectasis and/or honeycombing on HRCT. Results Ninety-five subjects were included (mean age 63±10 years; 81% female). Pulmonary fibrosis was present in 80%, although only 20% were classified as definite or probable usual interstitial pneumonia (κ=0.52). Individuals with fibrosis had lower FVC (75%±17 vs 86%±15, p=0.02) and worse QCT measures (%high-attenuation areas −600 to −250 HU 12.1±6.6 vs 5.5±0.8, p<0.001; lung volume 3407±958 mL vs 4077±923 mL, p=0.015). In 24 months, FVC and QCT measures remained stable. Eight subjects (8%) died. Deaths were not preceded by measurable functional or radiological decline. Health-related quality-of-life scores and blood biomarkers remained unchanged. Conclusions In this predominantly mild RA-ILD cohort, pulmonary function and QCT metrics remained stable over 2 years despite an 8% mortality rate. The absence of preceding decline in conventional prognostic markers suggests potential limitations of current monitoring strategies, although our findings should be interpreted as hypothesis-generating. Trial registration number NCT04136223 .