Choosing a new doctor is never easy. You need to know about convenience factors, such as office location, available appointment times, and accepted insurance plans. You will probably also consider background information, such as education, board certifications, and licenses. But the most important question you likely have involves results: Is this doctor any good?

Unfortunately, there just isn’t a single, perfect way to measure the quality of individual doctors. No matter how we approach the issue, we will always be looking at just one slice of overall physician performance. To see what I mean, let’s examine some ways to think about evaluating quality.

Health outcomes

In a perfect world, the health outcomes of other patients would show us which doctors are best. Better doctors have healthier patients, right?

However, it’s not that simple. To accurately detect trends, you need a lot of data. Because physicians handle so many different types of problems, getting enough of one kind of data to compare is nearly impossible. Not even specialists, who have a narrowed focus, see enough similar cases to detect statistically-valid trends. Hospitals are bigger, so they can at least measure how groups of doctors do on the whole, but this still doesn’t help in evaluating an individual doctor’s quality.

Guideline compliance

Since it’s not practical to choose based on health outcomes, how else might we compare physicians? The next most obvious potential solution is guideline compliance.

In almost every medical situation, there are guidelines – essentially checklists –that doctors should follow. We could grade doctors based on how strictly they follow these rules. Better doctors would be better at following rules, right?

Again, it’s unfortunately not that simple. A sloppy surgeon might leave every patient with a dangerous infection, yet still get a perfect compliance score, because she always performs the recommended procedure in the recommended way at the recommended time. In other words, a static set of guidelines is never complex enough for real-world medicine. It just can’t help us understand who the highest quality doctor may be.

Patient adherence

It’s not all bad news, though. There is a hidden, underreported way to measure quality when finding a doctor: the human factor.

As a young neurologist, I worked in a headache clinic. Many of my new patients came to me addicted to the pain medications originally prescribed to treat their headaches. When they stopped taking the medicine, they would get withdrawal headaches. It was a vicious circle. To help them, I needed them to ride out the difficult withdrawal process until they were “clean.” In my experience, the most effective way to make this happen was to build a great rapport with them. It was a struggle, but the power of our emotional connection was enough to help many patients break the addiction cycle.

Think of your own experiences as a patient. Imagine if a doctor you didn’t like told you to exercise three times a week, or wear a certain SPF daily, or take a specific medication weekly. Would you trust or respect that physician’s recommendation enough to do so? Would you even schedule a basic follow-up appointment?

This is a critical issue in medicine. For physicians, the ability to build great relationships with patients isn’t just good manners; it also has an effect on adherence. Adherence, in medical terms, is simply how well a patient follows medical advice. If patients don’t stick to the plan, it is much harder to help them get well (and stay that way), which is of course your doctor’s primary job. This is reflected in the trend toward physicians utilizing motivational interviewing techniques.

This is especially true for office appointments (versus a surgery), where results depend on how well patients follow prescriptions and recommended behavior modifications. That’s why, everything else being equal, adherence is very important to good health.

How to measure patient adherence

This is where things get interesting. Since good relationships mean better health outcomes, one of the best ways to measure a physician’s quality is to look at their patient reviews in categories like “bedside manner.” You can ensure that reviews are authentic by using closed-loop review systems, which I discussed in more detail here.

But isn’t every rating subjective? What if a patient was just having a bad day when he left a scathing review? Yes, that is a concern. And that’s exactly why we should look at ratings in large numbers. The more reviews a doctor has, the more fair and representative they become, and the more they can tell you about that doctor.

Of course, as I mentioned earlier, there is no perfect way to judge doctor quality. But that’s why it’s so fortunate that health care consumers have these new tools at our disposal. Closed-loop review systems are currently one of the most powerful ways to discern doctor quality. And best of all, the power to create reviews, share them, and utilize them is right where it belongs — in patients’ hands.

Oliver Kharraz is chief operating officer and founder, ZocDoc. He blogs at The Doctor Blog.