title: A longitudinal study of lung function in nonsmoking patients with rheumatoid arthritis.
abstract: OBJECTIVE
  s: 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.
authors.affiliation: Department of Respiratory Medicine, Glasgow Royal Infirmary, Glasgow, UK. j.fuld@bio.gla.ac.uk
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Fuld
authors.forename: Martin K
authors.initials: MK
authors.lastname: Johnson
authors.forename: Mark M
authors.initials: MM
authors.lastname: Cotton
authors.forename: Roger
authors.initials: R
authors.lastname: Carter
authors.forename: Simon W
authors.initials: SW
authors.lastname: Watkin
authors.forename: Hilary A
authors.initials: HA
authors.lastname: Capell
authors.forename: Robin D
authors.initials: RD
authors.lastname: Stevenson
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012044:Regression Analysis; D012129:Respiratory Function Tests; D013997:Time Factors