D-dimers

and Martina Feichter, medical editor and biologist

Martina Feichter studied biology with an elective subject pharmacy in Innsbruck and also immersed herself in the world of medicinal plants. From there it was not far to other medical topics that still captivate her to this day. She trained as a journalist at the Axel Springer Academy in Hamburg and has been working for since 2007 - first as an editor and since 2012 as a freelance writer.

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The D-dimers are cleavage products of fibrin. They are used to rule out thromboembolism, which is a sudden blockage of a vein or artery by a blood clot. Here you can read everything you need to know about the D-Dimer reference range for children and adults and possible causes for increased and decreased measured values!

What are D-Dimers?

The D-dimers are breakdown products of the fiber protein fibrin, which plays a major role in blood clotting:

The accumulation of fibrin and blood platelets (thrombocytes) forms a blood clot - both in healthy blood clotting (wound healing) and in the pathological formation of blood clots (thrombi) within intact vessels. Such thrombi can block a vessel at the place of their formation (thrombosis) or they can be carried away with the bloodstream and cause a vascular occlusion elsewhere (embolism).

When a plug or blood clot dissolves (fibrinolysis), the cross-linking strands in the fibrin are split. This results in smaller fibrin fragments, including the D-dimers.

When do you determine the D-dimers?

The doctor determines the D-dimers from a blood sample if a thromboembolism (such as leg vein thrombosis, pulmonary embolism) or excessive blood clotting (disseminated intravascular coagulation) is suspected.

The following symptoms in the affected extremity provide an indication of a vascular occlusion in the legs:

• swelling
• Dull pain
• bluish coloration (cyanosis) due to insufficient oxygen supply
• overheat
• Feeling of heaviness or tension
• distinct protrusion of the veins

D-dimers as a method of elimination

The “D-dimer test” has a low specificity, but a high sensitivity. On the one hand, this means that increased values ​​do not directly indicate a specific clinical picture - a positive test result can therefore have many causes and is of little use to the doctor in diagnostics.

On the other hand, it also means that the test is very sensitive to vascular occlusion: in patients with a normal D-dimer value, vascular occlusion is very unlikely. Therefore, the laboratory value is well suited to clarify the suspicion of a vascular occlusion.

D-dimers: normal values

The D-dimer level in the blood of adults is usually between 20 and 400 micrograms per liter (µg / l).

Caution: In women, towards the end of a pregnancy, the D-dimer value naturally increases to a certain extent, without this having a disease value. The doctor must take this into account when assessing the laboratory value.

When are the D-dimers lowered?

If the D-dimer values ​​are below the so-called cut-off, this is irrelevant.

When are the D-dimers elevated?

The cause of increased D-dimers is usually a thromboembolic event, i.e. a blood clot that blocks a vessel. The D-dimer value is increased in almost all patients with deep vein thrombosis and falls back to the normal range within a few days to weeks.

In addition to deep vein thrombosis, the following diseases or situations are a possible cause of increased D-dimers:

• other thromboses or embolisms (such as pulmonary embolism, heart attack, etc.)
• Disseminated intravascular coagulation (DIC, consumption coagulopathy)
• Operations
• heavy bleeding
• Cirrhosis of the liver
• Hemolytic uremic syndrome (HUS)
• Cancers
• Inflammations such as "blood poisoning" (sepsis)

D-dimers: pregnancy

There is a natural increase in D-dimers during pregnancy. At the same time, pregnancy carries an increased risk of blood clots forming. The upper limit above which the doctor must consider a thromboembolism in a pregnant patient is higher than in other patients (see above: D-dimer values: table for pregnant women).

What to do with changed D-dimers?

If the D-dimers are increased, a vessel occlusion is possible. The doctor will clarify this suspicion promptly so that any necessary countermeasures can be taken immediately.

If, for example, a pulmonary embolism is suspected, a so-called CT angiography makes sense - a computed tomographic examination of the blood vessels with the help of a contrast agent. In addition, the doctor can perform an ultrasound examination of the heart (echocardiography): As a result of the pulmonary embolism, the right ventricle is stressed, which is then noticeable in the examination, for example, through a ventricular widening or a weakness of the heart valves concerned.

If the doctor suspects thrombosis of the arms or legs as the cause of the increased D-dimers, a special ultrasound examination is also used (so-called compression and color duplex sonography). This will allow the doctor to identify the suspected blood clot.

If a patient's symptoms and risk factors make a vascular occlusion very likely, the doctor will perform an imaging test such as CT angiography even if the D-dimer readings are normal.

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