© 2003 American Thoracic Society
Identifying Smokers at Risk of COPD and GOLDTo the Editor:In their article, Vestbo and Lange (1) discuss the concept of identifying subjects at risk for COPD. They wrote "The single-breath nitrogen test was regarded as a promising candidate in the 1970s and 1980s but turned out to be too unspecific for subsequent use in both epidemiology and clinical medicine... This test, as well as others (e.g., mid-expiratory flows), may well be able to demonstrate small changes in the airways; however, these changes are not indicative of more serious changes taking place and thus they lack predictive value." The authors are quoting our study (2) as supporting their assertion. In fact, the conclusion of our study is at variance with their assertion. It is well known that although cigarette smoking is the cardinal cause of COPD, clinically overt disease develops in only a minority of smokers. Our objective was to identify high-risk smokers and to assess the prognostic significance of "small airways" tests. In a follow-up for 13 years of 56 former steelworkers, smokers and ex-smokers, two indices, FEV1/VC and the single-breath nitrogen test, identified at the start of the study those subjects who reached at its end FEV1/VC values as low, or lower than 45%. These values are observed in the clinical stages of the disease. It is worth mentioning that 13 years earlier all these subjects were active "blue collar" workers in their 50s. It appears that in a middle-aged smoker a decreased FEV1/VC ratio has no serious implication in itself. Only an associated increased single-breath nitrogen test adds the necessary information to predict a serious functional deterioration.
Université Catholique de Louvain Brussels, Belgium FOOTNOTES Dr. Vestbo was given an opportunity to respond to this letter, but declined to do so. REFERENCES
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