Investigation of blood level of D-dimers is a valuable method for excluding deep vein thrombosis and pulmonary embolism. However, the examination is little bit tricky and when not used wisely, it may sometimes bring more problems than benefits.
D-dimers are protein fragments that are formed during dissolving of blood clots. To be more precise, D-dimers are degradation products of fibrin. When the blood clotting is excessive, so is the dissolving of blood clots as the organism tries to keep these two processes in equilibrium. Increased formation of blood clots therefore means high blood concentration of D-dimers. The level of D-dimers may be easily evaluated from a sample of venous blood.
D-dimers are typically elevated in deep vein thrombosis and pulmonary embolism. Their concentration is also high in extensive inflammatory processes (infections, autoimmune processes, spread malignant diseases, conditions after injuries, post-surgical period, etc.)., in pregnancy, in liver diseases and in elderly patients.
The main disadvantage of D-dimers in the diagnostic approach is their low specificity. Low level of D-dimers is great in exclusion of deep vein thrombosis and pulmonary embolism, but their high value is present in many patients who do not suffer from the above-mentioned conditions. Therefore, we should D-dimers only as a supportive method in patient who have some symptoms of thromboembolic disease (chest pain, shortness of breath, etc.), but when we evaluate the possibility of pulmonary embolism as less probable and we want to rule it out once and for all.
If the patient has clear clinical symptoms of thromboembolic disease and our suspicion is high, it is advisable not to examine D-dimers, but rather perform an imaging method that can confirm the condition (ultrasound of the lower extremities in deep vein thrombosis, CT angiography of lungs or lung scintigraphy in pulmonary embolism).