Background/Purpose: Since there is broad variability within the studies investigating this issue, it is not possible nowadays to reliably establish prevalence and incidence of rheumatoid arthritis-associated interstitial lung disease (RA-ILD). Epidemiologic data is fundamental to measure the socio-healthcare relevance of diseases and contribute to satisfactory healthcare planning. The objective of this study is to determine the frequency and the incidence of primary lung involvement in early RA including ILD.

Methods: A prospective study in an early RA (1987 ARA or 2010 ACR/EULAR classification criteria for RA) cohort of patients diagnosed between 2003 and 2023 has been carried out. In the first visit they were asked about respiratory symptoms, were auscultated seeking Velcro crackles, and underwent a chest X-ray (CXR) and pulmonary function tests (PFT) with spirometry and DLCO. In the presence of symptoms, crackles, or alterations in CXR/PFT, a high-resolution computed tomography (HRCT) was done. The screening was repeated between the second and the fifth year of evolution of the disease in patients without initial pathologic findings. Frequency, cumulative incidence (CI) at 3 and 5 years, and incidence rate (IR) for the detected different lung manifestations were calculated.

Results: One-hundred-eighty-seven patients with RA who had a time from symptoms onset ≤ 12 months were included. Incidence and frequency data are described in Table 1 and Table 2, respectively. CI of ILD was 5.4% (95% CI 2.5-10.0) at 3 years and 8.2% (95% CI 4.5-13.7) at 5 years, and IR was 14.9 cases per 1000 person-years (95% CI 9.7-22.0). After a mean of 10.2 years of follow-up per patient, a final frequency of 21.4% was observed. In 17.5% of cases ILD preceded joint manifestations by months or years, while in 32.5% it was coincident with RA debut. In 20% of patients ILD was asymptomatic or paucisymptomatic by the time of diagnosis. NSIP pattern was slightly more frequent than UIP pattern, and 82.5% of patients evolved to a fibrotic pattern (fNSIP and UIP). Follicular bronchiolitis incidence, with a CI of 3.4 and 5.5 at 3 and 5 years, respectively, and an IR of 7.6 cases per 1000 person-years, was significantly lower compared to ILD incidence, as also was the frequency (8.6%). Non-traction bronchiectasis were the most documented manifestation, with an IR of 21.5 cases per 1000 person-years and a frequency of 23%. Other complications included pulmonary rheumatoid nodules (5.3%), pleural disease (3.7%), interstitial lung abnormalities (4.8%), and bronchiolitis obliterans (1.1%). Pleural disease preceded joint symptoms in some cases too.

Conclusion: The frequency of RA-ILD in our study was 21.4%. The CI was 5.4% at 3 years and 8.2% at 5 years, and we found an IR of 14.9 cases per 1000 person-years. It has been argued that airway involvement is more frequent than interstitial involvement in RA. However, in our study the frequency of bronchiolitis was lower than the frequency of ILD. Certain pulmonary manifestations, such as ILD and pleural disease, can be the first clinical presentation of RA (extraarticular-onset rheumatoid disease).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/primary-lung-involvement-in-early-rheumatoid-arthritis/