Patients may overestimate benefits of screening programs, preventive medicines

Patients overestimated the risk reduction achieved with screening and preventive medications, and clinicians should keep that tendency in mind when discussing such issues with patients, a study found.

To assess patients' expectations about screening and prevention, researchers surveyed them about the benefits of screening for breast and bowel cancer, as well as drugs to prevent hip fracture and cardiovascular disease. Researchers mailed questionnaires to all registered patients ages 50 to 70 years from among the panels of three general practitioners in Christchurch, New Zealand.

The questionnaire examined expectations of benefit for four specific preventive measures: a breast cancer screening program already offered in New Zealand, a bowel cancer screening in a pilot phase in one region of the country, and treatment with preventive medications for cardiovascular disease and hip fracture. Results appeared in the November/December Annals of Family Medicine.

The questionnaire asked participants to select how many deaths or fractures would be avoided in a group of 5,000 people ages 50 to 70 years undergoing the specific interventions for 10 years: 1, 5, 50, 100, 500, or 1,000. Responses were then compared to the actual expected benefits of the studied interventions. Next, the questionnaire asked the study population to indicate the minimum number of lives saved or hip fractures prevented they believed might justify the intervention.

Of 977 patients invited, 354 (36%) completed the questionnaire. Among the four scenarios, 90% of participants overestimated the effect of breast cancer screening, 94% overestimated the effect of bowel cancer screening, 82% overestimated the effect of medicine to prevent hip fracture, and 69% overestimated the effect of medication to prevent cardiovascular disease.

Most respondents also set their minimum benefit that would justify the interventions higher than what the treatments actually achieve. Cardiovascular disease prevention was the one exception to this finding. Although the study was performed outside the United States and the response rate to the survey was relatively low, the results suggest that the tendency to overestimate benefits may affect patients' decisions to adopt such preventive interventions, and practitioners should be aware of this when talking to patients, the researchers noted.

“[D]octors should be aware that many patients have overly optimistic expectations of the benefits of preventive interventions and screening,” the authors wrote. “This misperception may impair informed decision making about the use of such interventions, and physicians should consider using decision aids with patients when discussing these interventions.”