As a med student, I was explaining the colonoscopy procedure my patient was scheduled for by describing the small camera we would use to view the walls of his colon. This man was quite the character and one of my all time favorite patients. As I explained he quipped, “I just have one question, Doc. Where you gonna put the flasher?”

We shared a good laugh, but the reality is that medical screening tests are no joke. Tests are recommended based on an evaluation of the science and economics.  Unfortunately, it’s not always clear if the benefits of a screening test outweigh the costs.

Over the course of history we’ve had some big wins when it comes to medical screening. The Pap smear, for example, is a minimally invasive, low cost test.  It’s responsible for lowering the cervical cancer incidence and death rates in the U.S. by 60 percent since the 1950’s. Moreover, this was accomplished by detecting mainly precancerous lesions. It isn’t a perfect test by any stretch, but in the world of medical screening, it’s about as good as it gets.

False Positives and False Negatives

Unfortunately, every screening test, including the Pap smear, comes with its own set of worries. False negatives occur when a screening test misses the presence of disease.  You have your colonoscopy and get a clean bill of health. You think all is well, but six months later you see the doctor for digestive symptoms that lead to a diagnosis of colon cancer. It was probably there for a year or two. If the number of false negatives is high, the cost of the test can prove too high for the benefits it provides.

On the other end of the spectrum is the false positive. This is when you're told you have a disease, or at the least a pre-disease, when you actually don’t. The problem here is that it leads to unnecessary treatment. This extra treatment may be minor - a repeat pap smear, for example. But sometimes, the treatment can be more invasive.  For example, a high Prostate Specific Antigen (PSA) test often leads to prostate biopsy.

There are also financial costs associated with further medical intervention. It is estimated that the extra cost of care for a woman with a false positive mammogram is $503 over the year following her test. Assuming a conservative false positive rate of 5-6%, this adds up to a billion or more in additional medical expenses each year.

Overdiagnosis

As technology races along, we find ourselves facing yet another problem with screening tests. Overdiagnosis is the detection of disease that would never have turned into a noticeable problem. We’re detecting cancers earlier and earlier. People are thrilled when their disease is “caught early”. But Gilbert Welch, MD, author of Overdiagnosed, explains that overzealous medical testing can “trigger overdiagnosis and overtreatment.”

The thing is, our immune systems provide constant monitoring of cell changes. Cancerous cells are often controlled or destroyed before they are able to cause havoc in our bodies. Sometimes screening tests find diseases that our body would have managed for us. This can lead to treatments like surgery or radiation that are unnecessary. The problem is that we have no way of knowing which cancers the body would have controlled and which would have become something serious.

So we treat everything we find.

How to Decide Which Screening Tests are for You

The US Preventive Services Task Force (USPSTF) and Medical specialty boards, such as the American College of Obstetricians and Gynecologists or the American College of Surgeons all have their own screening recommendations. These organizations look at how screening tests decrease disease incidence and prolong lives. They also consider the cost of screening and the potential for unnecessary treatments.

The problem is they don't all agree.

This issue received media attention in 2009 when the USPSTF changed their recommendations for breast cancer screening. The new approach was opposed by the American Cancer Society and the American College of Radiology. There was outrage. In November 2013, the USPSTF announced a plan to review the benefits and risks of mammograms and plans to revise their recommendations in the near future.

The point here is that screening tests are based on populations. But you’re not a population. You’re an individual with a unique family history, unique health behaviors and unique values that determine how aggressive you want to be in preventing all kinds of disease. This is where your relationship with your doctor comes into play.  Be sure you work together to find a screening program that is exactly right for you.