Emergency department (ED) patients presenting with nontraumatic abdominal pain express greater confidence in decision making when CT is included in the diagnostic evaluation; however, their understanding of radiation exposure is poor, according to a study in the January issue of Annals of Emergency Medicine.

Over the last decade, ED physicians increasingly referred patients for abdominal pelvis CT imaging, partially because CT “has been demonstrated to increase emergency physician certainty of diagnosis, decrease the need for emergency surgery from 13 percent to 5 percent, and avert up to 24 percent of proposed hospital admissions,” wrote lead author Brigitte M. Baumann, MD, of the department of emergency medicine at the University of Medicine and Dentistry of New Jersey in Camden, N.J.

In the wake of growing concerns about CT overuse and estimates that may attribute cancers in the U.S. to radiation exposure during CT imaging, Baumann and colleagues sought to assess patient expectations regarding CT imaging. The researchers noted that an FDA initiative to curb unnecessary radiation exposure suggests that patients track their imaging history and share data with physicians.

“If patient expectations for imaging are high or if their understanding of radiation risk is poor, then efforts to reduce unnecessary radiation exposure from such imaging may pose an even greater challenge for healthcare providers,” offered the researchers.

Baumann and colleagues established three goals for the study. They aimed to establish patient confidence levels in a continuum of medical evaluations that started with a physician-conducted history and physical exam to one that included abdominal pelvis CT imaging according to a 100-point confidence scale. The researchers assessed patient knowledge of radiation exposure, asking them to compare CT to chest x-rays. Finally, they measured patients’ understanding of risk associated with CT imaging, based on level of agreement with statements about cancer risk and asked patients about their CT imaging history.

The study population was comprised of 1,168 patients aged 18 years or older who presented to the ED at Cooper University Hospital in Camden, N.J. with nontraumatic abdominal pain lasting 72 hours or less from March 2008 to May 2009. Sixty-seven percent of the patients were female, and mean age was 40.7 years.

Baumann and colleagues found that patient confidence increased with increasing levels of diagnostic intervention. Specifically, median confidence in medical evaluation with a history and physical exam stood at 20 on a 1 to 100 scale. It rose to 84 with the addition of blood work, 85 with the addition of blood work and ultrasound and 90 with the addition of blood work and CT.

Despite patients’ confidence in CT imaging, the researchers reported that patients had minimal understanding of radiation exposure. “When asked to compare the amount of radiation from an abdomen-pelvis CT to a 2-view chest radiography series, more than 70 percent underestimated the relative amount,” wrote Baumann.

Researchers also presented patients with two statements regarding CT risk. “[Two to three] abdominal CTs give the same radiation exposure that survivors of Hiroshima received.” and “[Two to three] abdominal CTs over a person’s lifetime can increase the chances of cancer.” Median level of agreement reached 13 and 45 on a 1 to 100 scale, respectively.

When asked about CT imaging history, 365 patients reported no previous CT imaging, but when researchers checked EMRs, they found that 39 percent of these patients had a documented CT scan within the last five years.

The researchers acknowledged several limitations to the study, recognizing that the urban demographic may not be generalizable to other settings or populations. Some participants also failed to respond to the question about CT radiation dose compared to chest x-ray dose. (A recent study presented at RSNA 2010 suggests the radiation risk may be lower than the threshold used in this study.)
 
As experts continue to debate whether or not CT can increase cancer risk and vendors attempt to drive down dose, the ED researchers suggest that dose reductions programs need to include another element.

“[O]ur findings suggest that efforts to reduce unnecessary medical imaging will need to not only address healthcare provider practices but also include patient education and awareness,” summed Baumann and colleagues.