Key Results

A total of 913 patients were enrolled. The median age was 45 years, and 56 percent of the population was female. The vast majority of this population identified as Caucasian and had attended at least some college. Overall, 54 percent of patients chose to get a head CT.

The percentage of patients who chose to get a head CT decreased when the education and information provided by the clinicians was paired with the offer of $100. Subjects were also more likely to choose foregoing CT when the reported potential benefit was decreased or when the reported potential risk was increased. 

• • Primary Outcome: 
    • When the potential benefit was reported as 0.1 percent, 49.6 percent of subjects wanted a CT; when the potential benefit was reported as 1 percent, 58.9 percent wanted a CT (odds ratio [OR], 1.48; 95 percent confidence interval [CI,] 1.13–1.92).
    • When the risk was reported as 0.1 percent, 59.3 percent of people wanted a CT; when the risk was reported as 1 percent, 49.1 percent wanted a CT (OR, 0.66; 95 percent CI, 0.51–0.86).
    • When no money was offered, 60 percent of people wanted a CT; when $100 was offered to forgo the CT, 48.3 percent of subjects wanted a CT (OR, 0.64; 95 percent CI, 0.49–0.83).
  • Secondary Outcomes: When adjusted for various potential confounders including age, gender, race, income, level of education, and prior history of health problems, the results remained consistent.

Evidence-Based Medicine Commentary

1. External validity: The vast majority of this population was highly educated and Caucasian. There was also a high percentage (24 percent) who worked in health care. This might impact the external validity to other practice populations.
2. Health literacy: The authors did a good job explaining the potential risks and benefits of each scenario in multiple ways. However, in the group told the CT would confer a potential benefit of only 0.1 percent, with a 1 percent harm, 50 percent of people still wanted a CT scan. That means even among subjects who were explicitly told their chance of harm was 10 times their chance of benefit, half still wanted a head CT. This may suggest that the patients did not really understand the meanings of these numbers or that the immediate potential benefits described to them were seen as more valuable than delayed potential harms.
3. Unintended consequences (ie, increases in ED visits for low-risk head injuries): Would offering cash result in a perverse incentive for a patient to present multiple times to the emergency department with a reported low-risk head injury in the hopes of getting $100 not to get a scan? This would have to be considered.
4. Health inequities: There are many examples of health inequities in society. Offering money not to have an unnecessary test may add to this problem. A $100 cash incentive may influence a patient at the lower end of the socioeconomic spectrum compared to a patient at the higher end. Do we really want to reinforce or increase health care gaps based on money rather than the potential benefits and harms of the intervention?
5. Financial incentive: Who would pay the $100 financial incentive? Would it come from the hospital? Private or public insurance providers? Would it be deducted from the patient’s copayment? (In this study, the cash was intended to be a reduction in one’s expected copayment.)
6. Bottom line: Money, potential risks, and potential benefits can all influence a patient’s behavior in requesting an unnecessary head CT scan.

Case Resolution

You explain to your patient that it is very unlikely she has a serious head injury based on the CCHR. After discussing the risks of a head CT scan and the negligible chance of benefit, she is happy to forgo the scan. Appropriate concussion discharge instructions are provided.

Thank you to Dr. Justin Morgenstern, an emergency physician and the creator of the excellent #FOAMed project called First10EM.com, for his help with this review.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.