Clotting
D-dimeer
A breakdown product of blood clots; in healthcare mainly used to rule out thrombosis or pulmonary embolism with acute symptoms.
Everything about this testWhat it measures
D-dimer is formed when the body breaks down a blood clot. A clot consists of a network of fibrin threads; when it dissolves, fragments are released, including D-dimer. Normally there is very little D-dimer in the blood. The value rises when a clot is formed and broken down somewhere in the body, such as with a deep vein thrombosis or pulmonary embolism, but also after surgery or injury, with inflammation and during pregnancy.
- Clot formation and breakdown in the body, such as with a deep vein thrombosis or pulmonary embolism; can only be interpreted together with the symptoms and a doctor's assessment
- Increased clotting activity after surgery or injury, with inflammation or during pregnancy
- Disseminated intravascular coagulation (DIC): a derailment of clotting in very ill people
High
A raised D-dimer means that more clots are being formed and broken down in the body than normal. This is not specific: according to the Dutch Society for Clinical Chemistry (NVKC), the value also rises after surgery or injury, with an infection, liver or kidney disease, during pregnancy and with cardiovascular disease, and the value increases with age. Rarely: a malignant condition. A raised value can fit a deep vein thrombosis or pulmonary embolism, but does not make that diagnosis; that requires an ultrasound of the leg or a CT scan. In people without symptoms of thrombosis, a raised D-dimer usually cannot be interpreted.
Low
A normal or low D-dimer makes a recently formed blood clot unlikely. In healthcare, the GP only rules out a deep vein thrombosis or pulmonary embolism with a low D-dimer together with a decision rule that weighs the symptoms and the physical examination; the test is then done on the same day. A low result from a test that is only known days after the symptoms started therefore does not rule out thrombosis. With the use of anticoagulants, the value can be low even though there is a clot.
If your result is abnormal
With a raised D-dimer without symptoms of thrombosis, usually no ultrasound or scan follows; the GP looks for an explanation such as recent surgery, infection or pregnancy. With symptoms that fit a deep vein thrombosis or pulmonary embolism, the GP uses a decision rule and a new same-day D-dimer test to assess whether an ultrasound of the leg or a CT scan in hospital is needed.
Reliability
D-dimer is a rule-out test: the test is very sensitive, but not very specific. A normal value makes thrombosis unlikely, a raised value proves nothing. According to the Dutch GP guideline (NHG) and the Dutch medical specialists' guideline (FMS) on antithrombotic treatment, the test is only reliable in combination with a clinical decision rule, with symptoms that started recently and with a result on the same day. D-dimer rises with age, so in older people the test is more often raised without thrombosis; that is why laboratories often use an age-dependent cut-off from the age of 50.
Limitations
- The result of this test is only known after a few days; that is too late to rule out thrombosis with acute symptoms.
- After surgery, injury or infection, during pregnancy and at older ages, D-dimer is often raised without thrombosis.
- Anticoagulants can lower the value, even when there is a clot.
- D-dimer is sensitive to the blood draw and transport: the plasma must be separated within a few hours and frozen if needed.
How common is this
A deep vein thrombosis or pulmonary embolism occurs in an estimated 1 to 2 in 1000 people per year in the Netherlands; the risk rises sharply with age and is higher after surgery, with long periods of bed rest, during pregnancy and with use of the contraceptive pill. A raised D-dimer is much more common than thrombosis, especially in older people.
Who is this useful for
This test is not meant for ruling out a deep vein thrombosis or pulmonary embolism yourself. With a swollen, warm or painful leg, sudden shortness of breath, pain when breathing, chest pain or coughing up blood, call your GP or the out-of-hours GP service (huisartsenpost) straight away; there, D-dimer is measured on the same day if needed, together with an assessment of the symptoms. A result that is only known days later is too late for that. In people without symptoms, a D-dimer says little about the risk of thrombosis; the value then only has meaning if a treating doctor asks for it and takes the result into account.
Downsides and risks
- People who order this test with acute symptoms instead of calling the GP or out-of-hours GP service straight away lose valuable time; a pulmonary embolism can be life-threatening.
- A raised D-dimer without symptoms is common, especially in older people, and can lead to needless worry and unnecessary scans.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results