The D dimer blood test is a useful laboratory test that can help doctors determine why a patient is exhibiting specific symptoms. This test is not usually done on a routine basis. Instead, it is often performed in emergency room settings or by a private physician when a patient complains of pain or other symptoms.
D dimer is a protein fragment that is found in the blood after someone has had a blood clot. Fibrinolysis breaks down the clot, leaving D dimer in the blood. The D dimer blood test is usually performed when doctors suspect that a patient has a pulmonary embolism (blood clot in the lung) or deep vein thrombosis. While a negative test usually means that a blood clot is not present, a positive test does not necessarily indicate a blood clot or deep venous thrombosis. The D dimer level can also be elevated due to infection or trauma to the surrounding tissues.
When the D dimer blood test is ordered, a phlebotomist draws a sample of blood from a patient’s vein. This vein is usually located in the arm, although other veins can be used if the veins in the arm are not usable. Once the sample is drawn from the arm, it is taken to the laboratory and processed to determine the result. The ordering physician is notified of the test results and further testing or treatments may be ordered based on the result.
If the test is positive, other diagnostic tools can be used to determine if the patient has deep venous thrombosis or a pulmonary embolism. This is often done using a CT scan with contrast. During this procedure, the patient is given a radioactive dye intravenously. The dye highlights the area being scanned, which is the chest. Doppler ultrasound can be used to check for deep venous thrombosis. This scan is performed by running an ultrasound transducer along the veins of the legs. The ultrasound can help to detect any clots or blockages and give doctors the opportunity to treat the condition before it becomes more serious.
ClotCare Online Resource. “What is the D-dimer test?” Retrieved January 31, 2009. Available: ClotCare