Blood test results that fall out of normal range.

Should I be worried about blood test results that fall out of the normal range?

DEAR DOCTOR K

Last week I received the results of some recent blood work. A few of my values fell just outside the normal range. My doctor says it’s fine, but I’m still worried. Do I need to be?

DEAR READER:

A printout of lab results typically indicates normal ranges for each blood test next to your personal results. If your personal result is right in the middle of the normal range, you’ll likely feel relief.
But what if your result is at the very low or high end of normal, or even slightly outside the normal range? Should you worry? Unfortunately, there’s no straightforward answer. Here’s why.
With most blood tests, different laboratories would all come to pretty much the same result. However, with some tests there is more variation in the results from one lab to the next.
Another source of variation is you. The levels of many molecules in our blood change, sometimes from hour to hour. Blood sugar levels, for example, vary depending on what and when we ate. Other results are affected by how hydrated you are. Other results change with age.
The genes you inherited can affect results and may cause your results on particular tests to be outside the normal range every time tests are done. The question is not whether the result is “abnormal,” but whether it is becoming even more “abnormal.”
Results that change significantly over time are important even when a lab result is normal. For example, I had a patient whose PSA test for prostate cancer was in the low normal range every year for 20 years. Then, one year it was in the high normal range — still normal, but quite different for him. I caught his prostate cancer at an early and curable stage.
There’s no magic about the cutoff point for calling a test result abnormal. Just as in the man with prostate cancer, a result in the normal range can still be a sign of disease. And results that are outside the normal range (“abnormal”) don’t mean a person has a disease.
With some tests there is danger if the result is abnormally high or abnormally low. With other tests, it’s worrisome only if the abnormality is in one direction.
So, here’s my general advice for dealing with laboratory test results. If the results are near abnormal or definitely abnormal, and your doctor says not to worry:
• Suppose that the result has changed significantly from when it was tested previously. If so, ask if that change means it should be tested again sooner than usual.
• Suppose that the result is well into the abnormal range (not just over the line), but has not changed significantly. (For example, if a liver test has a normal range of 30-50, and your result remains 80, that is more worrisome than if your result remains 52.) If your result is way outside the normal range, ask if there are any diseases that the result could indicate, and any other tests for those diseases that should be ordered. more