Do you really need that screening test?

Screening tests can save lives, but are Canadians too obsessed with medical tests? 

By Danielle Martin, MD

Do you really need that screening test?
Photography by John Hyrniuk
As a family doctor, I often see patients in my office who feel well and hope to stay that way. Like me, they believe that an ounce of prevention is worth a pound of cure. Understandably, my patients hope that medical technology can stop them from getting sick, or detect their illnesses early enough to make a difference in their outcomes.

Pap tests for the early detection of cervical cancer, mammograms for breast cancer and blood tests for diabetes and high cholesterol are just a few examples of the screening tests both sought after by patients and recommended by doctors. News of Angelina Jolie's preventive double mastectomy sent women to my door.

The use of some screening tests is well-supported by scientific evidence: Screening can save lives when it allows us to detect illnesses and treat them. That's why major public awareness campaigns have taken place across Canada to encourage people to undergo tests of various kinds.

Why, then, do I feel that I often spend as much time talking my patients out of screenings as I do recommending them? It's because of the very real negative consequences faced by individuals, and the health-care system, when we are overscreened for illness.

How can overscreening be bad for your health? First, some tests can be directly harmful. Mammograms, for example, involve radiation, which can (over time) contribute to an increased risk of cancer. Colonoscopies carry a one in 1,400 risk of bowel perforation. And all tests carry the risks of what are known as “false positive” results, which can lead to enormous anxiety, as well as invasive investigations such as biopsies. In a recently published book on the topic of overdiagnosis, three U.S. physicians raised the possibility that detecting disease early does harm by leading to false labelling and inappropriate treatment, and can make people – who are otherwise well – feel sick.

The harmful effects of unnecessary screening tests are also clear at the system level. Health-care costs are rising in Canada, and not just because of our aging population: Canadians are undergoing more tests today than we did 20 years ago, with no obvious resulting improvement in our health. An article in the Archives of Internal Medicine estimated that removing typical but not useful screening tests, prescriptions and procedures from regular checkups could put billions of dollars back into the health-care system, where that money can be used for much-needed treatments, equipment and services.

There are initiatives in place all over the country to try to reduce inappropriate uses of screening tests while still using them where they have been shown to improve people's health. This process often requires physician and patient education. For example, recent changes to Ontario's guidelines for the frequency of Pap smears (from once a year to every three years for low-risk women) and for the start of bone mineral density testing (not before age 65 unless the individual has risk factors for osteoporosis) reflect the best available scientific evidence. But unless patients participate, it may take years to see changes in practices and the resulting health-care savings.


Here's a helpful breast self-exam guide you can follow before getting a screening. 

This story was originally titled "Do you really need that test?" in the September 2013 issue.

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