CT Scans May Be Helpful in Detecting COPD

Computed tomography (CT) scans may be helpful in identifying patients with chronic obstructive pulmonary disease (COPD), according to a recent study published in the Journal of the American Medical Association.

The study, which was conducted within an ongoing lung cancer screening trial, used prebronchodilator pulmonary function testing with inspiratory and expiratory CT scans to determine the accuracy of CT scans in identifying COPD. Both scans were performed on the same day on 1,140 male patients between July 2007 and September 2008. The average age of participants was 62.5 years.

Researchers then used the results of the pulmonary function tests to determine whether the CT scans accurately diagnosed patients with COPD. Data for self-reported respiratory symptoms was available for 1,085 participants, with 41% reporting physician-diagnosed emphysema and 93% reporting physician-diagnosed bronchitis. Based on the results of the pulmonary function testing, 38% of patients were classified as having COPD.

The final diagnostic model for the study included five independent factors associated with COPD: CT emphysema, CT air trapping, body mass index, pack-years (the number of packs of cigarettes smoked per day multiplied by the number of years the person has smoked) and smoking status. Using the point of optimal accuracy, the model identified 274 participants with COPD with 85 false-positives, a sensitivity of 63 percent, a specificity of 88 percent and a positive predictive value of 76 percent. This corresponds to a COPD-diagnosis for 63% of participants.

“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,” the authors wrote. “[Further], the additional scan can be obtained within the five minutes needed for lung cancer screening, so a substantial amount of extra scan time is not required.”

The researchers note that quantitative CT scans cannot replace pulmonary function testing as a primary screening method for COPD.