JAMA: CT may detect COPD during lung cancer screening

Chronic obstructive pulmonary disease (COPD) is a major cause of death in heavy smokers, yet it remains substantially underdiagnosed. There are some promising signs, however, as researchers have shown that low-dose inspiratory and expiratory CT scans obtained for lung cancer screening of men who are current and former heavy smokers can identify patients with COPD, according to a study published in the Oct. 26 issue of Journal of the American Medical Association.

Pim A. de Jong, MD, PhD, of the department of radiology at University Medical Center in Utrecht, the Netherlands, and colleagues wanted to determine if CT-based lung cancer screening could be a cost-effective way to identify participants with COPD at an early stage.

They hypothesized that CT-based lung cancer screening could allow physicians to acquire information on the presence of COPD without additional pulmonary function testing. Since air trapping assessment using chest CT has been established as a technique to quantify small airway dysfunction, the scans from lung cancer screening could provide additional information on the presence of COPD.

Researchers performed a single-center prospective cross-sectional study within an ongoing lung cancer screening trial. A total of 1,140 male patients had unenhanced CT scans from the cancer screening analyzed between July 2007 and September 2008.

Results showed that the automatic analysis was able to identify 274 participants with COPD out of the 437 participants who had COPD according to lung function testing for a sensitivity of 63 percent. The model also resulted in 85 false positives for a specificity of 88 percent.

“The conclusion of this study is that CT scans obtained within a lung cancer screening setting are reasonably accurate for the diagnosis of COPD, and this may be a strategy to enhance cost-effectiveness of lung cancer screening,” de Jong said in an accompanying interview published online. “This study is important because lung cancer screening is a very active area of research at the moment with the National Lung Screening Trial (NLST) results being published, but cost-effectiveness is still awaited and we provide a strategy to possibly improve cost effectiveness.”

The researchers noted that most COPD cases in the study were newly diagnosed, and the condition was predicted more accurately in symptomatic than in asymptomatic participants, though separate models for symptomatic and asymptomatic participants did not improve results.

“If CT screening is widely adopted for lung cancer screening, an additional benefit may be early detection of COPD,” wrote the authors. “Early diagnosis is important because smoking cessation early in the COPD disease process slows disease progression and decreases morbidity and mortality.”

The authors said that the results of the NLST have sparked a discussion about the use of CT screening of heavy smokers, and this recent study may inform the debate over the most effective way to implement lung cancer screening. Because heavy smokers also die from conditions besides lung cancer, such as COPD, a screening process that provides information on multiple conditions may be useful.

“If the results of this study are validated and confirmed and are found to be generalizable, it may be reasonable to consider adding an expiratory CT scan to the (baseline) inspiratory CT scan for additional evaluation of COPD because this would improve diagnostic accuracy,” wrote de Jong and colleagues. “However, this possible strategy of using quantitative CT for detection of airflow limitation is not proposed as a primary screening method for COPD, for which pulmonary function testing is the preferred method.”

The authors said the sensitivity of the CT scans in the study are too low to recommend it as a primary COPD screening test separate from lung cancer screening.