Clinicians use the D-dimer test to look for evidence of a severe blood clot in a patient’s body. It’s most useful if a blood clot is suspected in the lung, or in a vein in the leg or pelvis.
Blood clots can be life-threatening, especially if they travel to the heart, brain or lungs. This makes detection, diagnosis and prompt treatment extremely important.
D-dimer tests can also be a used if a specific blood disorder is suspected, such as Deep Vein Thrombosis.
What does the test result mean?
If a D-dimer test is positive, it has detected an abnormally high level of cross-linked fibrin degradation products in the patient’s body. It shows that that a large clot (thrombus) has formed in the body and is breaking down – but it doesn’t say where or why.
A high level of D-dimer may point towards DVT, but it could be due to other factors too. These would include recent trauma or surgery, liver or kidney disease, infection and certain cancers. It can also be elevated during the course of a normal pregnancy but may indicate potential eclampsia.
A patient showing a normal D-dimer test result is unlikely to have any significantly large clots in their blood. Doctors generally agree that a negative D-dimer is particularly valid and useful when testing is carried out on low-risk patients. It’s most helpful when ruling out a clot as the reason behind a patient’s symptoms.
Note that D-dimer tests should be carried out in addition to other tests. It’s not a catch-all, merely an indicator, useful in helping to diagnose a disease or condition. Both normal and elevated D-dimer levels may give rise to further tests and follow-up.
Understanding the blood test basics
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