Why physicians need to interpret your lab results

acp new logoA guest column by the American College of Physicians, exclusive to KevinMD.com.

More than ever before, patients are receiving laboratory test results, with some of their numbers in bold or with “H”s or “L”s next to them. In some cases they’re getting them straight from the lab, in accordance with federal regulations. If not from the lab, they’re accessing their results on their physicians’ electronic patient portals. In some states, patients have always been able to request a copy of their results from the lab.

I support providing patients with their test results. It engages patients in their care, especially for conditions where it’s good to “know your numbers,” such as diabetes. Leaving patients wondering about test results, especially those ordered to evaluate symptoms that led the patient to see the doctor, can be anxiety-provoking, even if everything turns out to be “normal.”

Incorporating reporting of results in a practice’s workflow provides an additional layer of safety. If a patient expects a report and doesn’t get it, this may alert the physician to the fact that the results were never received by the office.  The old “no news is good news” approach disregards the benefits of communicating test results and creates opportunities for errors.

Although increased direct access to results can be a good thing, we must not forget that there is a big difference between raw results and those interpreted by the person who ordered the test. For the non-clinicians who read this blog, I would like to spend the next few paragraphs explaining that difference.

Often, I get asked to “check some labs” by a patient or another physician requests results of “recent labs.” There are thousands of laboratory tests. Usually, we order specific labs to answer specific questions generated by a patient’s history, examination, or personal risk factors, or to monitor ongoing treatments. There are tests that we order in persons who are not having problems to find conditions where early detection matters, such as diabetes or high cholesterol, and even that short list varies by a person’s age, gender, and other factors. Talking about “ordering some labs” without the contexts that I just described is like going to a restaurant and asking for “something from the menu.”

There is an old phrase about “throwing spaghetti against the wall and seeing what sticks.” Some people believe incorrectly that this is how we utilize laboratory tests — order lots of them, see which ones are abnormal, and that will tell us what’s wrong with a patient. (Or, if they’re all normal, the patient is OK.) That is not how most of us use the laboratory. The true meaning of abnormal and even normal results depends on the question that led to the test being ordered in the first place.

Where do the “H”s and “L”s or the “normal” ranges next to the results come from? Typically, at least once a year, each lab obtains specimens from a group of healthy persons, runs many different tests, and for each test determines a “reference range” using statistical calculations. The reference range usually covers the middle 95 percent of healthy persons, meaning that 5 percent of healthy persons will have a result that is above or below the “normal” range. Each lab may have a different reference range for each test. So, having a high or a low value doesn’t automatically mean that there is a problem, or that there isn’t.

This also means that a healthy person has a 1 out of 20 chance of having an abnormal test (a false positive test), which should make everyone think before ordering. Often these false positives lead to further testing, some of it potentially harmful and expensive.

How do we decide when an abnormal test result is significant? By thinking about the question, we were trying to answer when we ordered the test and knowing a few things about the reliability of the test. Some tests are great at ruling out specific conditions if they’re normal but not in telling us which of several possible diseases is the cause of an abnormal result, or vice versa. That is why we order tests after deciding what we are looking for rather than indiscriminately ordering lots of tests, and why we need to interpret the results instead of just looking for the “H”s and “L”s. Keep in mind that sometimes a “normal” test can be a sign of a problem, depending on the situation.

Here’s a non-medical example of how the same “result” can be interpreted differently, depending on circumstances. You’re home alone late one night in a quiet house, and you hear creaking in the attic. You know that the sound could from be any of a number of things, ranging from the trivial to the serious, so you incorporate additional knowledge to decide how to respond. If it’s a windy day, or it’s a noise that you’ve heard many times and know to be insignificant, you may ignore it. On the other hand, if there have been break-ins in the neighborhood in which the burglars hid in the attic, you may end up calling the police.

A physician’s interpretation of test results relies on knowing what each result might mean and using what we know about the patient to draw a conclusion.

Increasing patient access to their test reports has many potential benefits. However, as stated in a 2011 ACP comment letter to CMS, we must not forget “the value that physicians and other health care professionals bring to the interpretation of laboratory test results in support of health care decisions in collaboration with patients.”

Yul Ejnes is an internal medicine physician and a past chair, board of regents, American College of Physicians. His statements do not necessarily reflect official policies of ACP.

Image credit: Shutterstock.com

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