One of the first things we were taught in medical school was the pivotal role of thresholds in governing the human body. To trigger a nerve to fire or a muscle to contract, there must be a stimulus of electrical activity that exceeds a threshold value. If the threshold value is too low, muscles go into spasm and deadly rhythms develop in the heart.
Low thresholds, however, aren't just a problem for an individual's health. They are increasingly a problem for the health of our medical care system.
The threshold for diagnosis has fallen too low. Physicians are now making diagnoses in individuals who wouldn't have been considered sick in the past.
Part of the explanation is technological: diagnostic tests able to detect biochemical and anatomic abnormalities that were undetectable in the past. But part of the explanation is behavioral: We look harder for things to be wrong. We test more often, we are more likely to test people who have no symptoms, and we have changed the rules about what degree of abnormality constitutes disease (a fasting blood sugar of 130 was not considered to be diabetes before 1997; now it is).
Low diagnostic thresholds lead people who feel well to be labeled as unwell. Not surprisingly, some subsequently feel less well. In short, low diagnostic thresholds introduce more "dis"-ease into the population. Does that sound like a good thing for a "healthcare" system to do?
Diagnostic thresholds that are set too low lead in turn to a bigger problem: treatment thresholds that are too low. Diagnosis is the critical entry step into medical care — getting one tends to beget treatment. That's a big reason why we are treating millions more people for high blood pressure, diabetes, osteoporosis, glaucoma, depression, heart disease — and even cancer.
To have any hope of controlling healthcare costs, doctors will have to raise their diagnostic and treatment thresholds. And higher thresholds would be good for more than the bottom line. Less diagnosis and treatment of disease would return millions of Americans to normal, healthy lives. That's right: Higher thresholds could well improve health.
To understand why, consider the marginal patient, the person who has been turned into a patient because of a lower threshold. She is a woman, say, who is now told she has osteopenia, a loss of bone density that might lead to osteoporosis. This is a condition that wouldn't even have been noted in the past, but because of more bone density testing, it is now identified. Or he is, perhaps, a man who has been told he has prostate cancer of a type that wouldn't have been detected before the advent of the PSA test and a change in the rules about what constitutes an abnormal test and triggers a biopsy.
The woman may have a bone density that is, in fact, average for her age. Perhaps more surprising, the man also may have a cellular finding that is average — or, more precisely, typical — for his age.
Both are at extremely low risk to experience their "disease" in their lifetime. Consequently, the potential for treatment to help is extremely low, much lower than for patients diagnosed and treated using a higher threshold.
Another way to look at it is this: These marginal patients are at extremely high risk not to benefit from treatment.
Yet they face the same risk of harm from treatment. One common treatment for osteopenia can lead to ulcers in the esophagus and may even make bones more brittle with long-term use. The common treatment for prostate cancer leads many men to become impotent and/or develop bowel and bladder problems.
In short, low thresholds have a way of leading to treatments that are worse than the disease.
You might reasonably wonder: How did we get here? A big part of the story is, of course, money. Whether you are a drug company, a hospital or any other player in system, the easiest way to make more money is to encourage lower thresholds and turn more people into patients.
Lawyers get some credit too. While clinicians are sued for failure to diagnose or failure to treat, there are few corresponding penalties for overdiagnosis or overtreatment. Doctors view low thresholds as the safest strategy to avoid a courtroom appearance.
The movement to measure healthcare quality, however well intended, exacerbates the problem. Many performance metrics measure whether diagnostic tests and treatments are being ordered. Because good grades typically require action, not inaction, lower thresholds are encouraged. And the advent of electronic medical records has made these actions even easier, as more and more of us have the "one-click" option to order tests and treatments.
Finally, there's our medical culture. We are trained not to miss things, however unimportant those things are. And we are trained to focus on the few we might be able to help, even if it's only 1 out of 100 (the benefit of lowering cholesterol in those with normal cholesterol but elevated C-reactive protein) or 1 out of 1,000 (the benefit of breast and prostate cancer screening).
We believe this is what our patients — and the public — cares about. But it's time for everyone to start caring about what happens to the other 999.
H. Gilbert Welch is a practicing physician and professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice. He is the author of "Overdiagnosed: Making People Sick in the Pursuit of Health."