Abnormal Lab Results Don’t Always Indicate Problems

Q:  I recently visited the doctor and had some laboratory studies done as a part of my evaluation. One of the results my doctor’s office related to me showed that my carbon dioxide level was low. Since learning that, I’ve heard nothing from my physician and I am assuming that I’m okay. What does a carbon dioxide level measure and should I worry about my result?

A:  Interpreting lab results can be one of the more complex tasks facing physicians. Even more challenging is explaining these results to patients in a way that is respectful, accurate, and does not provoke unnecessary anxiety or confusion.

All lab results are published and reported within a range defined as "normal". Normal values are derived from measuring those values in large numbers of healthy people and then selecting a range that includes the most frequently recorded results. The most common values are then selected as normal – that means values that are normal for some people, but less common, technically become "abnormal".

To underscore the situation, when lab results are reported, the report lists the normal range first followed by the patient’s actual value. Any number below or above the normal range is indicated on the lab report and may loosely be interpreted as abnormal.

This is where the challenge arises, and one of the main reasons why physicians are encouraged to only order tests that are based on the clinical condition of the patient at the time of evaluation, as opposed to ordering a battery of tests. Several problems can result, as shown in the following examples.

Let's say a specific test is ordered for a person who is generally in good health. The test results fall just outside the "normal" range. Often, a physician will determine that this is of no clinical significance and choose not to pursue it further yet to be truthful, a phone call is made to the patient stating that their test was abnormal, but not to worry about it. For the patient, of course, this is easier said than done.

Another scenario occurs when several tests are ordered to establish information on a specific condition and a test expected to be normal is not. When considered in the context of the patient’s health, the challenge often faced is whether to go on a "hunting expedition" of sorts that can lead to more intense and invasive forms of testing. This type of investigation may put the patient at risk for complications and cost large sums of money, often to no purpose, while generating high levels of anxiety.

Sometimes test results are just plain wrong maybe due to an error in the laboratory or a malfunction of the testing equipment.

Under these as well as other circumstances, and so long as the patient is well, the next best step is to repeat the test.

I am and remain a strong advocate for complete honesty on the part of the physician as it relates to the availability of test results. As long as the doctor’s explanation of an unusual result is clear, accurate and not dismissive, patients should be comfortable with the explanation. On more than one occasion, I have had to tell a patient that a structure found on a CAT scan of the brain is really fine and nothing to worry about.

As is relates to your question, an abnormal carbon dioxide level is probably nothing to worry about (note the somewhat vague nature of this response) if you are not feeling ill and have no problems with the function of your kidneys. I hope that will help you sleep a little better at night.

From a purely statistical perspective, the more studies you pressure doctor to order (or in the case of full-body CAT scans and heart scans that you select yourself), the more likely you will be presented with an abnormal value and the decision of whether or not to look further.

My advice is to get only the tests you need, as recommended by your physician. Sometimes what you don’t know can’t hurt you and what you do know can.

"Your Health" provides easy-to-understand information about common health conditions.