Rising rates of injury can’t explain the increased use of emergency room CT scans

Anyone who works in an emergency room has surely noticed that more and more patients are getting CT scans. That would seem to imply that more and more ER patients are suffering from the types of critical injuries that CT scanners are most adept at finding, such as skull and cervical spine fractures, intracranial hemorrhages and lacerations of the liver or spleen.

But what if something else is going on? Maybe ER docs are ordering more CT scans because they want radiologists to tell them what’s wrong with their patients. (For an entertaining low-tech movie demonstrating this phenomenon, click here.) Or perhaps the tests have become more popular because the newer, faster machines make them more convenient. A cynic might even speculate that the tests are being ordered with greater frequency because doctors are trying to head off malpractice lawsuits over missed diagnoses.

If any of these scenarios is true, you’d expect to find that the number of injuries diagnosed would be rising along with the number of CT scans performed. So a trio of doctors from Johns Hopkins University in Baltimore decided to check it out.

They gathered data from the National Hospital Ambulatory Medical Care Survey, which is conducted by the U.S. Centers for Disease Control and Prevention. They found that the proportion of patients who came to the ER for an “injury-related condition” (such as a car accident) and got a scan during their work-up rose from 6% in 1998 to 15% in 2007. But while the frequency of CT scans almost tripled, the frequency of life-threatening injuries remained essentially flat -- 1.7% in 1998 and 2.0% in 2007. The difference wasn’t statistically significant, the researchers said.

So it would seem that CTs are being overused. What’s wrong with that? Several things, the Hopkins researchers said:

• It’s expensive. The annual cost of CT imaging rose from $975 million in 2000 to $2.2 billion in 2007 -- an increase of 123%. For the sake of comparison, the use of standard X-rays and ultrasounds grew by only 65% in that period.
• It clogs up ERs. Patients who got a CT were stuck in the emergency room 126 minutes longer than patients with similar injuries who didn’t get the scans, according to the CDC data.
• It’s dangerous for patients. Experts estimate that 1% to 2% of all cancers are the result of ionizing radiation delivered by CT scans. The National Academies determined in 2006 that one in every 1,000 people who gets 10 millisieverts of radiation will develop cancer, and a single “pan scan” of the head, cervical spine, chest, abdomen and pelvis adds up to 37 mSv, the researchers said.

The study was published in this week’s issue of the Journal of the American Medical Assn.

-- Karen Kaplan / Los Angeles Times