TABLE 2

Progression to chronic obstructive pulmonary disease (COPD) in active smokers with normal spirometry/low diffusing capacity of the lung for carbon monoxide (DLCO) versus active smokers with normal spirometry/normal DLCO

Group#At end of evaluation period
NormalWith COPD
Normal spirometry, normal DLCO97 (57/59)3 (2/59)
Normal spirometry, low DLCO78 (36/46)22 (10/46)
p-value0.009
  • Data are presented as % (n/N) unless otherwise stated. 59 active smokers with normal spirometry/normal DLCO and 46 active smokers with normal spirometry/low DLCO were followed over time with full lung function studies to determine the rate of progression to COPD. #: individuals with normal spirometry and lung volumes, and normal DLCO were followed for mean±sd 45±20 months; individuals with normal spirometry and lung volumes but low DLCO were followed for 41±31 months (p>0.4). : Chi-squared test.