Like shark attack and the lottery, unconscious bias influences cancer screening

August 17, 2018 by Garth Sundem, CU Anschutz Medical Campus
Credit: CC0 Public Domain

What do shark attack, the lottery and ovarian cancer screening having in common? It turns out our judgments about these things are all influenced by unconscious bias.

Humans are prone to overestimating the likelihood of extreme events. Blame it on availability bias—the tendency to judge the frequency of an event by how easy it is to recall examples from memory. Because you've seen Jaws and have daydreamed about what you would do with the Powerball jackpot (sure, you'd give half of it to charity...), it's easy to pull up vivid, emotional representations of these events. The availability of these events in your mind overshadows the much more common, much more mundane reality that you have 1-in-292,201,338 chance of winning Powerball, and even among beachgoers, the chance of being attacked by a shark is only about 1-in-11,500,000. Still, availability bias makes you overestimate the likelihood of each, keeping you out of the water and in the corner store buying tickets.

Now a study published in the Journal of Women's Health shows that availability bias may thumb the scale of a doctor's recommendations, as well. Survey results from 497 primary care physicians show that who have had cancer themselves, or experienced cancer with a family member, close friend, or coworker, are 17 percent more likely than doctors without personal cancer experience to act against established guidelines to recommend that low-risk women receive screening.

"Most doctors are pretty comfortable with the idea that our personal experience can make a positive impact on our practice—we've known someone and so it gives us insight into how to take care of in similar circumstances. This study helps us realize that sometimes it can go beyond that. Personal can impact our practice in a variety of ways," says Margaret Ragland, MD, pulmonary critical care specialist at CUHealth University of Colorado Hospital in Aurora, CO.

Screening guidelines are designed to do the most good while causing the least harm. In the case of cancer, this means screening the patients who have the greatest chance of hiding a dangerous cancer at a treatable stage. Screening routinely saves the lives of high-risk patients. But for low-risk patients, the cost and chance that false-positive results will lead to anxiety and even unnecessary treatments outweigh the minuscule chance of finding a dangerous, treatable cancer. In other words, for a population of low-risk patients, the harm outweighs the good.

"Some people may think, what's the harm in doing testing that's not indicated? I'm going to get a negative test and it'll make my patient feel better. But if you find something, it can lead to further follow up, causing complications, cost, and anxiety," Ragland says.

This is why, for women of average risk, screening for ovarian cancer is not recommended. And yet when presented with a vignette describing a woman of average risk, 31.8 percent of primary care doctors who had personal experience of cancer chose to offer this screening. By comparison, only 14 percent of doctors without personal experience of cancer offered screening.

Results come from survey funded by the Centers for Disease Control (CDC) and managed by study senior author Laura-Mae Baldwin, MD, University of Washington professor of Family Medicine. The survey collected responses from 3,200 randomly sampled physicians who provide to women, with the goal of discovering characteristics of providers that might be at the greatest risk of recommending care that conflicts with guidelines. Baldwin's goal is to identify and educate these potentially non-compliant doctors to help ensure that patients more uniformly receive the best possible care.

"The reasons that doctors with personal cancer experience may be more likely to not follow screening guidelines are complicated and we don't know all the answers," Ragland says. "But my hypothesis is that a doctor's personal experience may influence their assessment of risk. You see a patient in front of you and you may assess the risk to be higher than it actually is."

During the Discovery Channel's annual Shark Week, visits to Florida beaches go down. When large Powerball jackpots draw media attention, ticket sales go up (ironically, increasing the chance of a split pot and reducing the expected value of a ticket). And when a doctor's personal cancer experience makes the horror of the disease more available in his or her mind, the doctor may overestimate a patient's cancer risk and over-prescribe unneeded screening.

"We're physicians, but we also have life experiences," Ragland says. "What this study tells us is that in ways we may not be aware, for better and for worse, our may affect our practice."

Explore further: New iPad app could improve colon cancer screening rates

More information: Margaret Ragland et al, Physician Nonprofessional Cancer Experience and Ovarian Cancer Screening Practices: Results from a National Survey of Primary Care Physicians, Journal of Women's Health (2018). DOI: 10.1089/jwh.2018.6947

Related Stories

New iPad app could improve colon cancer screening rates

March 12, 2018
Say ordering a cancer screening test was as easy as booking a hotel room online. Would that improve screening rates?

Physicians' experiences with family and friends impact breast cancer screening

December 4, 2017
Results of a national survey of more than 800 physicians suggest that their experiences with patients, family members and friends with breast cancer are linked with their recommendations for routine mammograms. Specifically, ...

Expert explains the latest guidelines for mammograms

January 20, 2016
The USPSTF has issued another set of recommendations for breast cancer screening. What are they?

Prediction tool helps tailor lung cancer screening to patients

May 30, 2018
(HealthDay)—Personalizing the harm-benefit assessment of low-dose computed tomography (LDCT) screening for lung cancer can inform patient-centered screening decisions, according to a study published online May 29 in the ...

USPSTF recommends against ovarian cancer screening

February 13, 2018
(HealthDay)—The U.S. Preventive Services Task Force (USPSTF) recommends against screening for ovarian cancer in asymptomatic women. These findings form the basis of a final recommendation statement published in the Feb. ...

Recommended for you

Survey reveals how we use music as a possible sleep aid

November 14, 2018
Many individuals use music in the hope that it fights sleep difficulties, according to a study published November 14 in the open-access journal PLOS ONE by Tabitha Trahan of the University of Sheffield, UK, and colleagues. ...

Colder, darker climates increase alcohol consumption and liver disease

November 14, 2018
Where you live could influence how much you drink. According to new research from the University of Pittsburgh Division of Gastroenterology, people living in colder regions with less sunlight drink more alcohol than their ...

Want to cut down on your meds? Your pharmacist can help.

November 14, 2018
Pharmacists are pivotal in the process of deprescribing risky medications in seniors, leading many to stop taking unnecessary sleeping pills, anti-inflammatories and other drugs, a new Canadian study has found.

Your heart hates air pollution. Portable filters could help

November 13, 2018
Microscopic particles floating in the air we breathe come from sources such as fossil fuel combustion, fires, cigarettes and vehicles. Known as fine particulate matter, this form of air pollution increases the risk of cardiovascular ...

No accounting for these tastes: Artificial flavors a mystery

November 13, 2018
Six artificial flavors are being ordered out of the food supply in a dispute over their safety, but good luck to anyone who wants to know which cookies, candies or drinks they're in.

Simple tips can lead to better food choices

November 13, 2018
A few easily learned tips on eating and food choice can increase amount of healthy food choices between 5 percent and 11 percent, a new Yale University study has found.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.