Background/Purpose: Interstitial lung disease (ILD) is the extra-articular manifestation that most frequently worsens the course of Rheumatoid arthritis (RA) disease. Purpose: To describe the characteristics of RA patients with ILD. To asess the inicence rate of functional respiratory impairment in these patients.

Methods: This is a longitudinal prospective study. A cohort of RA patients diagnosed of ILD since Feb 2007 until Mar 2018 were recruited and followed up until lost of follow-up or end of study (May 2018) in a multidisciplinary team, carried by a pneumologist and a rheumatologist in a Tertiary Hospital in Madrid. The main variable was functional respiratory impairment: decline in percent predicted FVC of ≥ 10% since the previous visit. Pulmonary function was measured at baseline and in follow-up visits every 3-6 months. Covariables: a) sociodemographic, b) clinical (basal comorbidities, ILD type (non specific interstitial pneumonia [NSIP]; usual interstitial pneumonia [UIP], Others); c) pulmonary function tests (FVC%, DLCO%); d) laboratory tests (ESR, rheumatoid factor, anti-CCP); d) therapy (corticoids, disease modifying antirheumatic drugs (DMARDs) such as Azathioprine (AZA), Mycophenolate, Leflunomide (LEF) and Biologic Agents (anti-TNFs, Abatacept, Rituximab). Survival techniques were used to estimate the incidence rate (IR) of functional impairment, expressed per 100 patient-years with their respective confidence interval [95 % CI].

Results:

We included 43 patients, 63% were women, with a mean age at ILD diagnosis of 70±9.6 years. The most frequent comorbidities at baseline were: hypertension (65%), peripheral vascular disease (18.6%), and cerebrovascular disease (13.9%). 42% of the patients never smoked. Rheumatoid factor and anti-CCP was positive in 85% and 82% of the patients respectively, and the baseline ESR was 43±26. 32.5% had NSIP and 63% had UIP. The median values of FVC% were 103[84-111]. During the follow-up, 77% of the patients used corticoids; and regarding DMARDs patients used Mycophenolate (n=4), AZA (n=18), LEF (n=16), TNFs (n=6), RTX (n=20) and ABA (n=5). Functional impairment occurred in 16 patients (37%) with an IR of 17 [11.4-25.3] (141.4 patient-years of follow-up). 50% of the patients achieved funtional deterioration at 4.6 years since the diagnosis of ILD. Concerning the ILD types, IR for UIP was 18 [10.6-30.3] and for NSIP 15.7 [8.4-29.2]. The IR in patients taking corticoids was 15.3 [9.8-24.1]; LEF 13.2 [6-29.4]; AZA and Mycophenolate 17.4[8.3-36.6]; RTX 10.9[4-29.2].

Conclusion: Our RA patients were in their seventies and had active disease signs (higher ERS and Rheumatoid Factor positive) at the diagnosis of ILD. The most common radiological pattern was the usual interstitial pneumonia. The pulmonary function was mild at ILD diagnosis, maybe reflecting that our patients are diagnosed early in time. Functional impairment occurred in 37% of patients with an incidence rate of 17% patient-years, being 4.5 years the median time free of impairment. The crude incidence of functional impairment varies among therapies, being 10% for RTX. These results show the complexity of these patients and the need of futher multicentric observational studies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-course-of-interstitial-lung-disease-in-rheumatoid-arthritis-patients-in-clinical-practice/