D-dimers are formed during the breakdown of blood clots in the body. Their determination is most important when a patient is suspected of having deep vein thrombosis, pulmonary embolism, or other thromboembolic problems. However, the medical literature emphasizes that the study of D-dimers has some significant limitations - what do they result from? What are the standards for D-dimers? How to interpret the test results? What does a high level of D-dimers mean?

D-dimerswere first described in the 1970s, but only after about twenty years since then their determination began to be used in laboratory diagnostics. But what are D-dimers anyway: a new type of blood cell, an inflammatory protein, or something else? To get an idea of ​​what exactly D-dimers are, one needs to focus for a moment on the human coagulation system. In various situations, e.g. after a blood vessel damage, the activation of platelets (resulting in their accumulation and, in a way, "clogging" of the damage) occurs, but also the proteins of the coagulation system circulating in the blood plasma are stimulated. One of the most important of them is fibrinogen, which - under the influence of thrombin - is transformed into fibrin, the task of which is to create a specific scaffold for the entire resulting clot. However, the clot breaks down over time. Then, fibrin is broken down, where various products of its decomposition are formed - one of them is D-dimers. Under normal conditions, in a he althy person, D-dimer should therefore be absent. If these proteins appear, it means that the body must have formed a clot and then started to break down. However, the determination of D-dimer is not a routine test as is performed e.g. on all hospitalized patients, as is the case e.g. with blood counts. So when are D-dimers tested?

D-dimers: indications for determining the level of D-dimers

D-dimers are determined primarily in patients with suspected thromboembolism. An example of such a disease is deep vein thrombosis of the lower extremities. The suspicion of this disease, which is an indication for the examination of D-dimers, can be made after finding such symptoms in the patient,like:

  • pain in the lower limb (especially when putting pressure on the limb)
  • limb swelling
  • redness of the skin of the lower limb
  • increased warmth of the lower limb (especially when it is observed only in one of the two lower limbs)

Another problem that may constitute an indication for D-dimer testing is the suspicion of pulmonary embolism. Symptoms that - especially if they appear together - may suggest this disease, are:

  • sudden breathlessness with chest pain
  • hemoptysis
  • increase in body temperature
  • sudden and severe weakness
Important

D-dimers: test and standard

D-dimer testing is performed on a blood sample obtained from the patient. The standard of D-dimers may be slightly different in different laboratories, but most often the concentration of D-dimers lower than 500 µg / l is assumed as the value corresponding to the standard.

It should be emphasized here that in elderly people - especially in the absence of any ailments - the level of D-dimer, which is slightly above the norm, is usually not cause for concern.

Increased D-dimers - what do they mean?

Increased concentration of D-dimers in the blood occurs, as already mentioned, mainly in the case of various thromboembolic diseases. However, just because a patient has elevated D-dimers does not necessarily mean that they suffer from pulmonary embolism or deep vein thrombosis of the lower extremities. There are quite a lot of other possible causes of the increased concentration of D-dimers in the blood - this phenomenon may be encountered in patients:

  • with disseminated intravascular coagulation
  • with various neoplastic diseases
  • pregnant
  • with liver disease
  • with various inflammatory processes
  • with heart disease
  • who have been injured
  • who have undergone an operation

D-dimers: why is this parameter considered quite imperfect? ​​

The study of D-dimers is characterized by limited specificity - this is due to the fact that there are relatively many possible causes of the increased concentration of D-dimers in the blood, as presented above. Certain factors are also mentioned that may lead to false-positive results of D-dimer tests, for example in patients with elevated bilirubin levels and high blood triglycerides. D-dimer testing may show elevated levels of D-dimers when the patient is not really at allaccumulation of these proteins in the body.

The limited diagnostic value of the D-dimer test is also due to the fact that, in the case of the above-mentioned thromboembolic diseases, it is not possible to diagnose such diseases on the basis of the concentration of these proteins alone. Other tests (e.g. imaging) are necessary for this. Currently, the use of the D-dimer assay is focused on excluding thromboembolic diseases in patients with a low risk of developing units from this group.

Worth knowing

Medicine currently has a wide variety of studies, some of which are more familiar to patients (for example, blood counts or determination of cholesterol levels or ESR values), while other studies on a larger scale have been performed relatively recently and patients simply don't know much about them. The latter situation can be found in many different determinations, one of which may be D-dimer testing.

About the authorBow. Tomasz NęckiA graduate of medicine at the Medical University of Poznań. An admirer of the Polish sea (most willingly strolling along its shores with headphones in his ears), cats and books. In working with patients, he focuses on always listening to them and spending as much time as they need.

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