In my previous article, I tried to provide guidance on the many-faceted, extremely complex laboratory tests that definitely require specialist knowledge in terms of explaining the results and drawing conclusions. I also presented examples where a minor deviation from the normal value does not necessarily mean a disease. However, we also need to dispel the misconception that, in the case of a negative laboratory test, there is absolutely nothing wrong with the given patient. Written by Dr. György Temesszentandrasi.

Negative laboratory tests are not only about so-called false-negative or false-positive results.

On the other hand, these cover the fact – well-known in medical circles – that the percentage of the positivity of the given test really indicates the given disease and vice versa: in the case of negativity, the percentage of the given disease can be ruled out. And this value is of course not 100%.

Presented through an example.

When someone arranges to have the so-called tumor marker tests, you may think that you are covered in case of negativity. Unfortunately, this is not the case. If only it were that simple…

We put the blood into a machine, it tells us what kind of tumor the person is prone to, it says online that there are already a few of these cells in the body, and the treatment can begin (with robotic surgery, of course). This looks good in science fiction, but reality is still far from it.

The National Cancer Registry contains 87 types of tumor disease groups, and this does not include the various histological subgroups, so the number of different tumors is several times this number. There are barely a dozen tumor markers, and their reliability is not the highest. Because - as I wrote above -

a negative test result does not necessarily mean a tumor-free condition, as a positive result does not necessarily mean a malignant disease.

In the positive case, further tests are necessary, and there are many occasions where the background of a slightly elevated marker is fortunately not a tumor, but "only" inflammation, infection, or even an environmental cause (for example, smoking).

Or let's mention one of the world's most common diseases, high blood pressure, which, according to estimates, affected 1.3 billion people in 2019, 16% of the world's population.

He is called the "silent killer" for a reason. Not only is it often mild or does not cause any complaints, but in the case of high blood pressure, it can easily happen that the laboratory test does not show any abnormality.

If the hypertension is of renal or hormonal origin, there will be a difference in the blood, but not or not necessarily in the most common primary form. The diagnosis can and should be made with frequent and correct blood pressure measurements. That's why it's worth measuring your blood pressure from time to time, even if you're not complaining, because high blood pressure that's existed for a couple of years, and I emphasize that it's often completely symptomless, already manifests itself in complications.

But by definition, various psychological problems, that is, diseases of the soul, are not associated with laboratory abnormalities, even though their importance and frequency are increasing significantly in our fast-paced world.

A small overview of cultural history. Already in ancient times, Juvenalis wrote that "Orandum est, ut sit mens sana in corpore sano" , that is, "it is worth praying that a healthy soul dwells in a healthy body." So, contrary to popular belief, the saying did not originally mean what we attribute to it today. On the contrary. He drew attention to the fact that an apparently healthy body may indeed have mental problems.

And we could continue the series with nervous system diseases such as Alzheimer's disease or Parkinson's disease, where there are no necessarily pathological deviations during routine laboratory tests.

These examples also prove that someone can be sick even with normal laboratory results, that a medical screening test cannot be "completed" with a laboratory test alone, and they underline the fact that the attending physician needs to be attentive during the comprehensive care of his patient.

Author: Dr. György Temesszentandrasi

Photo: Tomwieden / Pixabay

A few sentences about the importance of laboratory tests (and dispelling a misconception)