Hot Off the Press: The Effect of Financial Incentives on Patient Decisions to Undergo Low‐value Head CT Scans

The CT scan is arguably the most important piece of diagnostic technology that we use in emergency medicine. It allows for incredibly rapid identification of a myriad of life-threatening conditions. However, likely because it is such a valuable tool, there seems to be little doubt that we overuse it. For example, one study that looked retrospectively at all head CTs ordered for trauma concluded that more than one-third were unnecessary based on the Canadian CT Head Rule.1 Not only does unnecessary testing reduce efficiency and add costs, it also directly harms patients with unnecessary radiation.2 Many imaging decisions are obvious—the patient either clearly requires or clearly does not require imaging. However, there is a great deal of uncertainty in emergency medicine, which leaves a sizeable number of patients in a gray zone—where harms and benefits are closely matched, qualitatively different, or just unknown. For these patients, shared decision making is probably the best route forward.3, 4 Furthermore, even when it seems clear to the physician that imaging is not required, we are often met with resistance from our patients. Thus, it is important to know what factors influence patients’ decisions to undergo CT. This study by Iyengar et al.5 examines the impacts of financial incentives, as well as varying levels of risk and benefit, on patient preference for CT imaging in the setting of low-risk head injury. This is a cross-sectional survey in which participants were presented with a hypothetical low-risk head injury scenario to assess their desire for diagnostic imaging. Participants were randomized to receive different estimates of risk and benefit (1% or 0.1%). They were also randomized to receive a hypothetical offer of either $0 or $100 to forgo imaging. They recruited 913 patients and overall 54% wanted imaging. Desire for CT decreased with lower benefit and higher risk and when money was offered to forgo the CT. This is a clever study examining an interesting question. However, using hypothetical scenarios probably limits external validity, as decisions made while healthy will not necessarily mirror those made when stressed and unwell, especially after a head injury. That being said, it is not clear which represent better decisions: those made while healthy and stress-free or those made in the heat of the moment when facing a high-stress emergency. External validity is further limited in this single-center study by the unique study population, with the majority of the participants being Caucasian and having at least some college education. Furthermore, it is interesting that nearly 25% of the participants worked in health care, which could significantly influence the results of this study. Finally, from the perspective of a physician who has only worked in Canada and New Zealand, the fact that more than half of patients wanted a CT despite the very-low-risk scenario seemed incredibly high, and we wonder whether these results would be replicated in other countries. Finally, it should be noted that the numbers used for harms and benefit in this study were hypothetical and designed to be easy to understand rather than to accurately represent the true harms and benefits of CT. Therefore, although the trends are likely true, the exact numbers would vary in real clinical scenarios. They enrolled a convenience sample of 913 patients. Overall, despite the low-risk scenario (in which the Canadian CT Head Rule would advise against imaging), 54% of patients stated that they would want a CT scan. A higher benefit of CT resulted in a greater desire for imaging, whereas a higher risk and the offer of a financial incentive decreased desire for imaging. Specifically, if the benefit was reported as 0.1% then 49.6% of people wanted a CT, whereas if it was 1% then 58.9% wanted a CT (odds ratio [OR] = 1.48, 95% confidence interval [CI] = 1.13 to 1.92). If the risk was reported as 0.1% then 59.3% of people wanted a CT, whereas if it was 1% then 49.1% wanted a CT (OR = 0.66, 95% CI = 0.51 to 0.86). Finally, if no cash incentive was offered then 60% of people wanted a CT, whereas if $100 was offered to forgo the CT then 48.3% of people wanted a CT (OR = 0.64, 95% CI = 0.49 to 0.83). One number really jumped out in this study. In the group of participants who were told that there was only a 0.1% benefit from CT but a 1% harm, half of people still wanted a CT. In other words, despite being explicitly told that the harms of CT were 10 times higher than the benefits, half still opted for the imaging. That is a shocking finding. It may be explained by qualitative differences in the harms and benefits (the harms are delayed, but the benefits are immediate). Or perhaps, despite the excellent efforts of the authors to display information in multiple ways, harms and benefits were simply misunderstood. Or perhaps the number represents informational bias, in which people assume more information is always better, and therefore will always prefer more tests. Whatever the reason, the desire for imaging even when the harms are known to outweigh the benefits is a fascinating finding in a study designed to examine excessive, unnecessary diagnostic imaging. Minh Le Cong ( @ketaminh ) I don’t agree with paying financial incentive to influence health care decisions. Ethically it’s similar to drug companies giving gifts to influence doctors decisions. Ken Milne ( @theSGEM ) responds We felt similar. Adding in $$$ incentives could create more health inequities and we had concerns about social justice aspect. Medicine is hard enough without having to consider these $$$ which could bias our management. Listen to the podcast. Pik Mukherji ( @ercowboy ) I work in NYC. My experience in a busy ED, with multiple referring services and urgent cares sending people for CT- is NOT that 50% still want one after we chat. 10-15% is generous. “It only takes a 1wk ICU stay (or a 3 hr head CT) to avoid a 15 min. convo.” Tim Montrief ( @EMinMiami ) Big thing that stood out to me (having lived in Ann Arbor for the first 20 some odd years of my life) The vast majority of these pts are highly educated and white. There was also a very high percentage (24%) that worked in healthcare. How might that affect external validity? Youri Yordanov ( @YordaYou ) This is so weird from our side of the atlantic …. Ken Milne ( @theSGEM ) responds Also on this side of the Atlantic but north of the US border. Michael Schweitzer Would there be a limit, like when the supermarket will only let you buy so many units of something on sale? Because I'd go twice a day to the ER to demand a CT head if this came true. Easy money. Imagine the hordes of folks who show up just to say “Oh well, if you don't think I need a CT for this large pimple on my forehead, I'll just take the cheque and go now.” Will Meurer responds Even in very-low-risk scenarios, patients demonstrate a desire for advanced diagnostic imaging. When the harms clearly outweigh the risks, we have a responsibility to protect our patients. However, when decisions are not clear cut, it is important to understand the various factors that influence patients’ decisions, so that we are able to guide our patients through an effective shared decision-making process.

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