Imagine a town with two barbers. One of them sports a magnificent haircut; the other’s head resembles the nest of a psychotic bird. Which one would you choose to cut your hair?

If your first choice is the immaculately coiffed one, stop to think about how things must work in this town. Since there are only two barbers, obviously they cut each other’s hair. If you’re looking for a great haircut, wouldn’t you prefer the person who created it to the one sporting it?

Now imagine a town with two doctors. All the patients of the first doctor have perfectly controlled blood pressure and diabetes. They all exercise regularly, none of them smoke, and all of them have received all age-appropriate preventive health screenings. Many of the other doctor’s patients, on the other hand, have blood pressure and glucose readings off the charts. Smokers are well-represented in the practice, and preventive health screenings are hit-or-miss.

Medicare’s recent “pay for performance” (P4P) initiatives purport to reward doctors financially for so-called “quality” care. According to the data, the first doctor in the above town would be raking in the bonus money, while the other would be facing stiff penalties.

But which one do you think is the better doctor?

What if the first doctor decided that the best way to improve his P4P data was to discharge all the patients from his practice who, for whatever reason, failed to achieve acceptable control of their blood pressure and diabetes? Or who didn’t stop smoking? Or who refused to get a flu shot, or go for a mammogram, pap smear, or colonoscopy? As it happens, there’s nothing in the Hippocratic Oath against discharging patients. With enough money at stake in a P4P arrangement, this is inevitable.

What happens to these people? They’d be in big trouble if the other doctor in town also refused to take care of them. By continuing to work with patients whose diseases are not as simple to control, who may be reluctant or unable to take time off from work to undergo preventive testing, or who are too ornery to follow medical advice even as they continue to seek it out, that physician is also providing “quality” care.

The biggest mistake made by Medicare, private insurers, and other entities seeking to improve medical care by rewarding “quality” is mistaking it for “performance”. One of the most egregious examples of this is the so-called “four hour rule” for antibiotics for pneumonia. Medical evidence does indeed support the idea that when patients have pneumonia, they do better the sooner they are begun on antibiotics. But by tying hospital compensation to a rigid four-hour rule, many more patients end up receiving unnecessary antibiotics when the diagnosis of pneumonia takes more than four hours to establish. The financial penalties from failing to meet the standard are significant; they can include risking the institution’s accreditation status. Thus, a “performance” standard results in a lower quality of care for many patients without pneumonia exposed unnecessarily to powerful medications.

Quality is like pornography; you know it when you experience it. But it cannot be measured; only assessed, and then only subjectively.

Quality in medical care has more to do with meeting the needs of individual patients and less to do with checking off boxes on a preventive care form. Some patients want detailed explanations of every facet of their medical care. Others prefer a more “Just the facts!” approach. The mark of a high quality physician is the ability to bring more than one style of communication to bear in meeting the needs of a varied patient base.

How well we succeed in controlling diseases that are primarily dependent on patients’ lifestyle choices is measureable, and therefore tempting to use as proxies to reward, but ultimately irrelevant. We need to be very careful when we talk about “quality” in medical care, because patients can easily end up with much more than a bad hair day.

Lucy E. Hornstein, MD has been a solo family physician in the Philadelphia suburbs for 18 years. She was born and raised in Washington DC (which has left her with a deep and abiding apathy for all things political) and attended college outside Boston before coming to medical school in Philadelphia, which, she has discovered, is a black hole. (No one born here ever leaves; no one who moves here ever leaves.) She has been blogging since August 2006 when she assumed the persona of "#1 Dinosaur," a nod to the impending extinction of primary care. She is the author of Declaractions of a Dinosaur: 10 Laws I've Learned as a Family Doctor, a memoir about her life in medicine.