At the same time, the Lung Health Study does not provide a rationale for mass population screening or even for screening in all smokers. Because it was well known that decreased lung function predictive of COPD can be observed in smokers in their 30s, 35 years of age was used as a cut-off point for screening. Thus, the results of the study provide justification for surveillance spirometry in a specific population at risk. At the same time, the study confirms that COPD is underdiagnosed: only 30% of those identified by spirometry screening as having mild COPD had received a diagnosis of “bronchitis” from their physician . It also shows that early detection can lead to highly successful intervention.