According to a study in the October 26 issue of JAMA researchers found that CT (computer tomographic) scans utilized for lung cancer screening showed that a significant proportion of current or former male smokers had chronic obstructive pulmonary disease (COPD). The finding suggests that CT scans could be utilized as an additional tool in detecting COPD.

According to background information in the article:

“Smoking is annually projected to cause more than 8 million deaths worldwide in the coming decades. Besides cardiovascular disease and cancer, chronic obstructive pulmonary disease is a major cause of death in heavy smokers. Nevertheless, COPD is substantially under-diagnosed. Despite a decrease in cardiovascular mortality and stabilization of cancer mortality worldwide, mortality from COPD is increasing.”

Giving up smoking early can prevent COPD progression, emphasizing the importance of early detection. CT-based lung cancer screening could be another strategy for detecting COPD in individuals at an early stage.

Onno M. Mets, M.D., of the University Medical Center Utrecht in The Netherlands and his team carried out a study in which they evaluated whether low-dose lung cancer screening CT scans could be used to identify participants with COPD. The study was conducted between July 2007 and September 2008 within an ongoing lung cancer screening trial and involved 1,140 male participants at an average age of 62.5 years, who had a prebronchodilator pulmonary function test with inspiratory (inhalation) and expiratory (exhalation) CT scans performed on the same day. The researchers determined the COPD diagnostic accuracy of the CT scans by using pulmonary function tests as the reference standard.

Of all participants’ 1,085 self-reported respiratory symptoms, with 566 participants reporting symptomatic symptoms and 519 reporting asymptomatic symptoms. Physician diagnosed emphysema was reported in 41 (3.6%) whilst 93 patients (8.2%) were diagnosed with bronchitis. The researchers established that 437 participants (38%) were classified as having COPD based on the results of pulmonary function testing.

The study’s final diagnostic model consisted of five factors that were independently linked to obstructive pulmonary disease. These included CT air trapping (abnormal retention of air in the lungs), body mass index, CT emphysema, smoking status and pack-years. Pack years were defined as the number of packets of cigarettes smoked daily multiplied by the number of years the individual has smoked).

By using the point of optimal accuracy, from a total of 437 COPD patients the model identified 274 (63%) participants with COPD with 85 false-positives, a sensitivity of 63%, a specificity of 88%, and a positive predictive value of 76%. Researchers established obstruction levels in these 274 participants as ‘mild’ in 54% (150 of 277) of all participants, ‘moderate’ in 73% (99 of 135) of all participants, and ‘severe’ in 100% (25 of 25) of all participants.

They comment:

“Our study findings suggest several practical considerations. 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. Although an additional ultra low-dose expiration CT scan increases the radiation dose, this exposure is limited. The additional scan can be obtained within the 5 minutes needed for lung cancer screening, so a substantial amount of extra scan time is not required.”

They continue by stating that they do not suggest using quantitative CTs of airflow limitation as a primary screening strategy for COPD, as pulmonary function testing remains the preferred method and conclude:

“A screening test should have a high sensitivity to identify most of the participants with unsuspected disease, and the performance of our strategy at optimal accuracy is not sufficient for CT to serve as a COPD screening test.”

Written by Petra Rattue