Objectives The aim of the study was to determine risk factors of interstitial lung disease (ILD) in patients with rheumatoid arthritis (RA).
Methods 111 unselected patients (94 women and 17 men) with RA, as defined by the 1987 ARA criteria, were included in the study. The diagnosis of ILD was based on high resolution computed tomography (HRCT) of the chest.
The following risk factors of RA related ILD (RA-ILD) were evaluated:
– demographic: age and gender,
– smoking status: current, former and cigarette pack-year,
– RA related: disease duration, Steinbrocker radiological stage, presence of atlanto-axial subluxation; presence of extra-articular manifestations (vasculitis, Sjögren syndrome, amyloidosis and subcutaneous rheumatoid nodules); activity indices assessed by both patient and rheumatologist (morning stiffness, tender and swollen joint counts, DAS28, VAS-pain, VAS-activity, HAQ, Steinbrocker functional class); laboratory test results (ESR, CRP, Hgb, PLT), serological markers (RF, ACPA, ANA, ENA)
– treatment related: methotrexate (MTX) use, duration of MTX use, MTX dose (current, cumulative and yearly; yearly MTX dose was defined as cumulative MTX dose/year of RA duration), prednisone use, cumulative dose of prednisone, other synthetic and biological DMARDs use.
Results The mean age was 60.7 years. Median duration of RA was 7 years.
Abnormalities consistent with ILD were found in 53 patients (47,8%).
Univariate analysis revealed significantly increased risk ofRA-ILD in patients with older age (per 5 years: OR 1,41; 95% CI 1,16-1,73; p- 0,001), presence of atlanto-axial subluxation (OR 4,39; 95% CI 1,33-14,46; p- 0,02), higher Steinbrocker functional class (OR 2,96; 95% CI 1,39-6,32; p- 0,01) and higher serum RF level (per 100 IU/ml: OR 1,22; 95% CI 1,05-1,41; p- 0,01). Cyclosporine A use (OR 0,31; 95% CI 0,12-0,79; p- 0,01), infliximab use (OR 0,12; 95% CI 0,01-0,99; p- 0,05) and treatment with higher current (per 5mg/week: OR 0,7; 95% CI 0,57-0,88; p- 0,002), cumulative (per 1000 mg: OR 0,74; 95% CI 0,58-0,95; p- 0,02) and yearly MTX dose (per 100 mg/1 year of RA: OR 0,74; 95% CI 0,62-0,88; p- 0,001) were associated with a significantly lower ILD risk.
Multivariate analysis showed following risk factors ofRA-ILD: age, serum RF level and yearly MTX dose. The risk of RA-ILD significantly increased with older age (per 5 years: OR 1,35; 95% CI 1,001-1,68; p- 0,007) and higher serum RF level (per 100 IU/ml: OR 1,16; 95% CI 1,001-1,36; p- 0,05), while higher yearly MTX dose significantly decreased the risk of RA-ILD (per 100 mg/1 year of RA: OR 0,74; 95% CI 0,61-0,9; p- 0,003).
Conclusions The independent risk factors of ILD in patients with RA were older age, higher serum RF level and treatment with lower MTX dose.
Disclosure of Interest None Declared
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