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In a recent issue of Thorax Bednarek et al1 presented interesting results from a large-scale prospective cohort study on the effect of combining spirometric tests with simple smoking cessation advice in 3077 middle-aged smokers with previously undetected airflow obstruction compared with smokers without airflow obstruction. Carbon monoxide-validated smoking cessation rates after 12 months of follow-up were 16% in subjects with airflow obstruction and 12% in smokers without airflow obstruction. These results are promising; however, we think that the authors’ conclusion that spirometric screening of chronic obstructive pulmonary disease (COPD) is effective in smoking cessation is too far-reaching because of the limitations of the study design.
The conclusion by Bednarek et al1 that spirometry is efficacious in smoking cessation is limited by the fact that their study was not a randomised controlled trial but a prospective cohort study comparing smokers with previously undetected airflow obstruction with those without airflow obstruction. This might have introduced bias. It is possible, for example, that the smokers with airflow obstruction in this study might have been more susceptible to the “health warnings” given by the doctor who evaluated the spirometric test results with them. This higher susceptibility to health warnings is indicated by the fact that the follow-up response rate was significantly higher among subjects with airflow obstruction (87%) than in those without airflow obstruction (62%), and that the follow-up response rate was associated with disease severity (90% in moderate to severe airflow obstruction compared with 81% in mild obstruction). Another problem is that neither prospective nor retrospective data appear to have been collected on whether smokers used pharmacological aids for smoking cessation on their own initiative during the 12 months of follow-up. The use of pharmacological aids for smoking cessation (such as nicotine replacement therapy, bupropion or nortriptyline) is more effective than behavioural treatment (advice) alone.2,3 It cannot be ruled out that this use was differential, meaning that smokers with airflow obstruction were more likely to use this form of treatment in addition to advice from the physician.
The results of the study by Bednarek et al1 are promising and in line with results from other studies.4,5 However, evidence from well designed randomised controlled trials is needed on the efficacy of spirometry for smoking cessation. Smokers with airflow obstruction probably respond differently to smoking cessation treatment than those without airflow obstruction. It has been shown in previous studies that the former group is more likely to be older, to be more addicted to nicotine and tobacco and to have a longer smoking history (and therefore more pack years)—all of which are predictors of treatment outcome.6 We therefore suggest that the use of spirometry for smoking cessation should be tested in a homogeneous group of smokers with previously undetected airflow obstruction who are randomised to undergo either counselling including confrontation with spirometry or councelling without confrontation. We are currently conducting such a trial (ISRCTN 64481813).
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Authors’ reply
We thank Dr Kotz and colleagues for their interest in our investigations and look forward to the results of their study.1 Our study did not confirm the opinion that spirometric tests showing normal lung function would encourage smokers to continue to smoke. We are aware that our investigations were not randomised and pointed this out in the discussion. This weakness was also stressed in the accompanying editorial by Mannino.2
With regard to possible bias introduced by the use of pharmacological treatment by smokers in our study during 1 year of follow-up, we would like to repeat that (1) in the study protocol smokers were asked to use their own motivation only to stop smoking and not to take pharmacological treatment, and (2) during the follow-up visit all subjects confirmed compliance with the protocol. Although we cannot exclude the possibility that deviation from the protocol may have occurred in some cases, it seems unlikely. Pharmacological treatment of nicotine dependence is not reimbursed and is relatively expensive in Poland. Bupropion is on prescription and only nicotine replacement therapy is available over the counter.
The suggestion that approaching younger smokers would be more rewarding is worth exploring. In our experience, airway obstruction is much less frequent (10%) in smokers aged 35–40 years than in older age groups. Since younger smokers are also less inclined to stop smoking, perhaps smoking cessation clinics would be more cost effective for this group than spirometric testing.