Medical screening tests, like Pap smears, cholesterol tests and mammograms, have been credited with saving countless lives, by catching diseases at their earliest stages.
But the author of a new book says many of these tests are being overused by well-meaning doctors and a medical industry that's motivated by profit and exploiting patients' fears.
Alan Cassels, a drug policy researcher at the University of Victoria and an expert adviser with EvidenceNetwork.ca, argues in his new book "Seeking Sickness: Medical Screening and the Misguided Hunt for Disease" that screening early and screening often doesn't always result in saved lives.
Many screening tests -- even simple blood tests -- often overpromise what they can do and rapidly turn perfectly healthy people into worried, overmanaged patients, he says.
Just this week, an expert panel in the U.S. recommended against routinely screening men for prostate cancer with PSA tests. The panel argued that the test often leads to unnecessary biopsies and treatments for tumours that are so small and so slow-growing, they'd likely never lead to symptoms or death.
Mammograms, too, have been shown to often lead to unnecessary testing and worrying in patients who probably never needed them in the first place.
"When you look at mammography or PSA testing for men, how many people do they have to screen to actually find disease and save somebody's life. When you look at those numbers, they have to screen thousands of people to save one life," Cassels told CTV's Canada AM from Vancouver Thursday.
"So the actual benefit of these tests for any person is really quite small and the potential for harm is quite large."
It's important to note that Cassels is making a distinction between medical screening and testing. Testing in those who are showing symptoms of illness always makes sense. But he questions whether screening otherwise healthy people for diseases they are not likely to have is wise.
He says patients who have worries because of family histories of disease should be encouraged ask their doctors about screening.
"If you're at higher risk, your benefit might be higher. But for average people, they really have to ask am I the appropriate person to be screened at this time?" he says.
Cassels laments that patients are not always aware that many tests have notoriously high levels of false positive rates -- meaning they will indicate there's a problem when there really isn't -- that can lead to unneeded stress and worry.
"Part of the problem with the sort of over-testing industry is that so many people go in thinking there can only be a positive, but you really have to go in with your eyes wide open, whether you're being tested for osteoporosis, high cholesterol even mental health screening," he says.
Other times, good and effective screening tests are being used on the wrong type of patient. The Pap smear, for example, is excellent at detecting cervical cancer, a "silent killer" that typically produces no symptoms until it's too late. But most women can stop screening after the age of 69 if they have had clear tests up that point, since their chances of dying from cervical cancer after that age is very small.
Still, the medical community and the media has done such a good job of promoting Pap tests, many assume that testing at any age makes sense. In his book, he relates the case of a 82-year-old woman walking into her doctor's office and asking for a Pap smear.
"The doctor described that to me and said his jaw hit the floor with a thud," Cassels says.
There are age limits for when doctors should start screening and when they should stop, but there are often pressures -- from patients groups, from the pharmaceutical industry and from overzealous patients themselves -- to push those limits too far, he says.
"When you start expanding the body of people you're going to be screening, you're actually increasing the potential for harm," Cassels says.
