On Screening

The current recommendations for cancer screening at all ages

SCREENING TESTS are emotional and controversial. They are done to detect the risk of health disorders or diseases in people who do not have any symptoms of disease, such as cancers, cognitive impairment (early dementia) and diabetes. In my years of practice, I have seen people who have been saved by screening tests not currently recommended by the Canadian Task Force on Preventive Health Care (CTFPHC), and I have also seen healthy people have significant morbidity, even death, as a result of invasive testing performed as a result of a positive screening test. According to Dr. Brett Thombs, Chair of the Canadian Task Force on Preventive Health Care, “Overdiagnosis, which is different from false positive or false negative screens, is the most concerning harm for the task force.” Screening tests have to be a joint decision between doctor and patient, once the potential benefits and risks are understood.

The CTFPHC was established by the Public Health Agency of Canada to develop clinical practice guidelines that support primary-care providers in delivering preventive health care. They use the research available to determine which screening tests are useful and which are not. The guidelines are regularly updated when new data becomes available.

Some of the most important screening tests are for cancer. A good cancer-screening test is one that is safe and that detects cancer early without many false positives (saying that cancer is there when it is not) or false negatives (saying that cancer is not there when it is). False negatives are harmful because they falsely reassure, and false positives are harmful in that they lead to unnecessary anxiety and potentially to further unnecessary tests, which may incur risks of their own.

It is important to note that general recommendations (below), apply to people at average risk. For more information, see canadiantaskforce.ca.