Abstract
This work was intended to evaluate the prevalence of obstructive small-airway disease in patients with rheumatoid arthritis (RA) and its association with clinical characteristics. Pulmonary function testing (PFT) and high-resolution computed tomography (HRCT) were performed on 189 consecutive RA patients. Each case was diagnosed based on abnormal HRCT findings. We defined obstructive dysfunction of small airways as a forced expiratory flow from 25% to 75% of vital capacity (FEF25–75) value >1.96 residual standard deviation (RSD) below predicted values. We found 19 patients (10.1%) with an interstitial pneumonia (IP) pattern and 15 (7.9%) with a bronchiolitis pattern; the other 155 (82.0%) had no abnormal HRCT patterns. In patients with neither abnormal pattern, median values of percentage predicted for carbon monoxide diffusing capacity (DLCO) and ratio of DLCO to alveolar ventilation (DLco/VA) were within the normal range, but median FEF25–75, forced expiratory flow at 25% of vital capacity (V25), and V25/height were <70% of predicted values. Forty-seven patients (30.3%) in this group had obstructive small-airway dysfunction. Multivariate logistic regression analysis indicated that this type of abnormality is strongly associated with respiratory symptoms [odds ratio (OR) 5.18; 95% confidence interval (CI) 1.70–15.75; p = 0.012), smoking history (OR 2.78; 95% CI 1.10–6.99; p = 0.03), and disease duration >10 years (OR 2.86; 95% CI 1.27–6.48; p = 0.012). Parenchymal micronodules, bronchial-wall thickening, and bronchial dilatation on HRCT scans were also predictive factors for abnormal FEF25–75, although these morphological changes were too limited for us to diagnose these patients with the bronchiolitis pattern. Obstructive dysfunction of small airways is apparently common among RA patients, even among those with neither the IP nor the bronchiolitis pattern on HRCT scans. Factors significantly associated with abnormal FEF25–75 are respiratory symptoms, smoking history, and RA duration.
Highlights
Rheumatoid arthritis (RA) is traditionally considered a chronic disease in which inflammatory changes occur predominantly in the synovial joints, but the systemic nature of this disease has been noted in clinical studies and daily practice
Measured values were compared with normal predicted values based on age, gender, and height of the individual, using regression equations installed in the spirometer; the equation for residual volume (RV)/TLC was formulated by Grimby and Soderholm [13], that for FEF25–75 by Schmidt et al [14], those for Peak expiratory flow (PEF) and V75 by Cherniack and Raber [15], that for V25/height (Ht) by Yamamoto and Mitsufuji [16], and those for DLCO and DLCO/VA by Burrows et al [17]
Multivariate logistic regression analysis with a backward stepwise selection procedure confirmed that the presence of respiratory symptoms, smoking history, and disease duration [10 years are significant factors independently associated with obstructive changes in small airways of RA patients who have neither interstitial pneumonia (IP) nor bronchiolitis high-resolution computed tomography (HRCT) pattern (Table 4)
Summary
Rheumatoid arthritis (RA) is traditionally considered a chronic disease in which inflammatory changes occur predominantly in the synovial joints, but the systemic nature of this disease has been noted in clinical studies and daily practice. We noted that a variety of morphological changes appear on HRCT scans in a considerable proportion of RA patients, though these abnormalities were too few for us to categorize such cases as belonging to the IP or bronchiolitis pattern It remained unclear whether such patients may have functional impairment of the lung and whether such abnormalities are related to RA. We performed pulmonary function testing (PFT) and HRCT scanning on 189 consecutive RA patients These were categorized according to their HRCT findings into the following three groups: patients with the IP pattern, patients with the bronchiolitis pattern, and patients who were not diagnosed with any abnormal HRCT pattern. We examined one or two predominant HRCT findings as well as the distribution and extent of abnormal findings and determined the probable diagnosis related to these pulmonary abnormalities according to the criteria on HRCT patterns defined by Tanaka et al [9]
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