Chest
Volume 124, Issue 4, October 2003, Pages 1224-1231
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Clinical Investigations
A Longitudinal Study of Lung Function in Nonsmoking Patients With Rheumatoid Arthritis

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Study objectives

Patients with rheumatoid arthritis (RA) have a high prevalence of pulmonary function test (PFT) abnormality, but the long-term significance of this is unknown. We performed a longitudinal study of pulmonary function in asymptomatic, nonsmoking patients with active RA requiring disease-modifying drugs. We looked for temporal change in lung function and characteristics that would predict subsequent development of PFT abnormality or respiratory symptoms.

Methods

In 1990, 52 patients (44 women; age range, 29 to 78 years; median, 56 years) underwent clinical assessment (drug history, RA severity, immunologic, and inflammatory markers) and PFTs (spirometry, body plethysmography, gas transfer). PFT results were expressed as standardized residuals (SRs). Thirty-eight patients were reassessed in 2000. A self-administered questionnaire was used to identify respiratory symptoms.

Results

The prevalence of pulmonary function abnormality was higher than expected compared with a reference population, but there was no significant increase in number over 10 years (8.7% in 1990 and 8.8% in 2000). When assessed by group means and compared with reference values, reduced diffusing capacity of the lung for carbon monoxide (Dlco) and increased ratio of residual volume (RV) to total lung capacity (TLC) [RV/TLC] were the only abnormalities to develop over the study period (mean Dlco in 2000, − 0.47 SR; 95% confidence interval [CI], – 0.91 to – 0.01; RV/TLC, 0.49 SR; 95% CI, 0.13 to 0.84). However, rates of change of pulmonary function variables were not significantly different from zero. Logistic regression did not identify any meaningful relationship between disease characteristics and PFT abnormality.

Conclusions

Asymptomatic patients with RA have a higher prevalence of PFT abnormality than expected, but these do not increase in number over time. We did not identify any patient or disease-specific characteristic that could predict the development of respiratory disease in patients with RA. Analysis using percentage of predicted values, rather than SRs, is misleading as it exaggerates the extent of abnormality present. Abnormal lung function is a common and probably benign finding in nonsmoking, asymptomatic patients with RA.

Section snippets

Recruitment

In 1990, we recruited patients from the RA second-line medication clinic at the Centre for Rheumatic Diseases at Glasgow Royal Infirmary. All patients had RA diagnosed by a consultant rheumatologist, according to American College of Rheumatology criteria,11and were receiving one or more disease-modifying antirheumatoid drugs (DMARDs). Inclusion criteria were lifelong nonsmoking, no documented or recalled evidence of lung disease, and absence of respiratory symptoms on general inquiry at initial

Results

We studied 52 patients (44 women; age range, 29 to 78 years; median, 56 years). Thirty-eight patients were seropositive, and all were receiving DMARD therapy with a median lifetime use of two agents (range, one to four agents). The DMARDs used and the number of patients prescribed them are as follows: IM gold (n = 25), sulfasalazine (n = 22), penicillamine (n = 11), hydroxychloroquine (n = 8), methotrexate (n = 4), and azathioprine (n = 3). Only three patients had been solely administered

Discussion

There have been a considerable number of cross-sectional studies looking at the prevalence of pulmonary abnormalities in patients with RA who were not known to have lung involvement. The older studies451718192021222324used PFTs to detect the abnormalities, whereas in more recent times this has been combined with HRCT of the thorax6725262728; all studies concur in that a high prevalence of abnormality (35 to 65%) can be found. By contrast, 27% of our population had pulmonary function

Conclusions

We have demonstrated that, within a population of patients with RA selected as lifelong nonsmokers with no respiratory symptoms, the prevalence of pulmonary function abnormality is higher than expected when compared with a reference population, but did not increase over 10 years. Assessed by group means and SRs, both Dlco and RV/TLC became significantly abnormal in 2000 when compared with reference values. However, rates of change of pulmonary function variables were not significantly different

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