What is D-dimer?
D-dimer, or Fibrin-D-Dimer, is a breakdown product that is formed when a blood clot dissolves in the body. When the coagulation system is activated, fibrin is formed to stop bleeding, and when this fibrin is later broken down by the enzyme plasmin in a process called fibrinolysis, fragments – including D-dimer – are released into the blood. D-dimer is therefore a marker of ongoing or recently completed coagulation and fibrinolysis activity in the body.
Normally, the amount of D-dimer in the blood should be low, but in conditions that lead to increased formation and breakdown of blood clots, the concentration of D-dimer in the blood increases. Therefore, the analysis is mainly used as a tool to rule out serious conditions involving blood clots.
Why analyze D-dimer?
D-dimer analysis is used in healthcare mainly to:
- Exclude deep vein thrombosis (DVT)
- Exclude pulmonary embolism (PE)
- Assess disseminated intravascular coagulation (DIC)
- Support the investigation of other conditions with suspected thromboembolism
The test is used primarily in acute situations where the patient exhibits symptoms that may be signs of a blood clot, such as pain, swelling or shortness of breath. In these cases, a negative D-dimer test – especially in combination with low clinical probability – may be sufficient to safely rule out a blood clot without the need for further imaging.
What does a high D-dimer mean?
Elevated levels of D-dimer indicate that there has been increased breakdown of fibrin, which in turn indicates that the body has had active clot formation and has begun to break it down. However, it is important to understand that the test is very sensitive but not very specific.
Elevated levels of D-dimer can occur in, among other things:
- Deep vein thrombosis or pulmonary embolism
- Infections and inflammation
- Postoperative condition
- Trauma
- Pregnancy
- Liver disease
- Cancer
- Old age
This means that an elevated D-dimer value is not sufficient to make a diagnosis on its own – it must always be interpreted in a clinical context and in combination with other examinations.
When is analysis for D-dimer useful?
D-dimer is particularly valuable in combination with a clinical assessment according to, for example, the Wells score for DVT or pulmonary embolism. If the probability of a blood clot is low and D-dimer is normal, a blood clot can in most cases be ruled out without further imaging.
It is important to note that the test has limited value in patients with elevated baseline levels of D-dimer, such as older individuals, pregnant women or patients with cancer. In these cases, the test can often give false positive results and should therefore be interpreted with caution.
Test your D-dimer levels
Measuring D-dimer can be crucial when a blood clot is suspected in the body, especially in emergency situations. Because the test is so sensitive, it can help to quickly rule out dangerous conditions and avoid unnecessary examinations. However, it is important that the sample is taken and interpreted by healthcare professionals in the right clinical context. The test is performed via blood test and can sometimes be part of larger investigations in cases such as unexplained pain, breathing problems or long-term swelling in the leg. In these contexts, D-dimer is often used as an initial screening before more advanced methods such as ultrasound or computed tomography are considered.