Although many believe that combined CT scans of the thorax are performed too often at many hospitals, a study published online April 24 in the Journal of the American College of Radiology suggests double scans are not being overused in the population at large.

Thoracic CT can be performed in three variations, and most radiologists agree that combined CT scans should be limited, wrote lead author David C. Levin, MD, of the Thomas Jefferson University Hospital and Jefferson Medical College in Philadelphia, and colleagues. A news article in 2011 reported that Medicare claims revealed considerable overuse of double CT scans of the thorax, so Levin et al conducted their study to determine what proportion of all thoracic CT scans are combined scans in the Medicare population.

Using the Medicare Part B Physician/Supplier Procedure Summary Master Files for 2001 to 2011, the researchers calculated utilization rates per 1,000 beneficiaries and the percentage that were combined scans from the three Current Procedural Terminology codes for thoracic CT.

Once the calculations were made, results indicated that the utilization rate of combined scans increased from 2001 through 2006, remained steady in 2007 and then sharply decreased after. This is reflected in the compound annual rate of change from 2007 to 2011, which was -10.4 percent.

From 2001 through 2006, combined thoracic CT scans were attributed to 6 percent of all thoracic CT scans. Notably, this percentage progressively declined from 2006 through 2011 and reached a low of 4.2 percent in 2011.

“Our data indicate that, contrary to the aforementioned concerns, the use of combined CT scans of the thorax in the Medicare population is actually quite low,” wrote Levin and colleagues. “Moreover, it seems to have decreased even further in recent years.”

The authors recommend that radiology groups practicing in hospitals use the 2011 figure of 4.2 percent as a benchmark when checking the CMS Hospital Compare website to determine their frequency of use of these exams in the outpatient population.