RHEUMATOID-ARTHRITIS LUNG-DISEASE - DETERMINANTS OF RADIOGRAPHIC AND PHYSIOLOGICAL ABNORMALITIES

Objective. To determine the prevalence and important clinical predicto rs of radiographic and physiologic abnormalities indicative of rheumat oid arthritis interstitial lung disease (RA-ILD). Methods. An unselect ed cohort of patients with a confirmed diagnosis of RA and known lung disease were identified (n = 336) and evaluated for RA disease activit y and severity. Outcomes included abnormalities determined by the pulm onary function tests of forced vital capacity (FVC) and diffusion capa city for carbon monoxide (DLco), and/or chest radiographic findings of interstitial infiltrates. We used multivariable statistical modeling to determine the independent significance of cigarette smoking and oth er RA-specific factors on the pulmonary abnormalities of interest. Res ults. At least 1 of the 3 abnormal findings was identified by pulmonar y tests in 32.4% of all patients. These abnormal findings included an FVC <80% of predicted in 42 patients, a DLco <80% of predicted in 64 p atients, and evidence of radiographic interstitial infiltrates in 40 p atients. After statistical adjustment for confounding factors, pack-ye ars of cigarette smoking remained a significant predictor of low DLco (beta = -0.07, 95% confidence interval [95% CI] -0.09, -0.04), low FVC (beta = -0.003, 95% CI -0.006, -0.0004), and interstitial abnormaliti es on chest radiograph (odds ratio for greater than or equal to 25 pac k-years = 3.76, 95% CI 1.59, 8.88). The Health Assessment Questionnair e (HAQ) Disability Index (DI) was also an important risk factor for th e decline in both the DLco (beta = -1.15, 95% CI -2.00, -0.30) and FVC (beta = -0.23, 95% CI -0.32, -0.13). Conclusion. Although RA disease activity/severity (particularly as defined by the HAQ DI) was importan t, smoking was the most consistent independent predictor of radiograph ic and physiologic abnormalities suggestive of ILD in RA.