D-dimer Test
The D-dimer test is a procedure that analyzes a blood sample to determine the presence of coagulation problems. It is useful for diagnosing or preventing strokeStrokeStroke , pulmonary embolism, or deep vein thrombosis.
General Description
D-dimer is a protein fragment produced when the body dissolves blood clots. Therefore, it is only found in the blood if the body has broken down or is in the process of dissolving a thrombus. The D-dimer test confirms the presence of blood clotting disorders if detected without a prior injury.
An abnormal presence of elevated D-dimer levels in the blood may indicate pulmonary embolism, deep vein thrombosis, disseminated intravascular coagulation (a condition that prevents proper blood clotting), or strokeStrokeStroke .
When is it Indicated?
The D-dimer test is indicated when there is suspicion of coagulation disorders due to the manifestation of several of the following combined symptoms:
- Swelling, pain, redness, or a warm sensation in the legs or arms.
- Difficulty breathing.
- Chest pain.
- Tachycardia (abnormally fast heart rate).
- Coughing up blood.
- Bleeding gums.
- Vomiting.
- Seizures.
- Stomach pain.
- Muscle pain.
Suspicion increases in high-risk individuals, such as long-term hospitalized patients, post-surgical patients, pregnant women, postpartum women, obese individuals, smokers, people with certain types of cancer, or those taking oral contraceptives.
How is it Performed?
To perform a D-dimer test, a blood sample is taken, usually from a vein in the arm. The procedure follows the same steps as routine blood tests:
- The patient sits or lies on a stretcher with their arm extended.
- The area is disinfected.
- A tourniquet is placed above the elbow to allow blood to pool in the forearm.
- A needle is inserted into the vein, and the tourniquet is released.
- The syringe plunger is drawn back to collect the blood.
- A bandage is applied to the puncture site.
Typically, one blood tube is sufficient. The sample is collected in the standard blue-capped tube used in routine blood tests. This tube contains sodium citrate to prevent clotting until the sample is processed for testing.
To prepare the sample, it is usually centrifuged to separate the cells from the serum. A recommended speed of 1500 g for 15 minutes is used to prevent alterations in the sample’s components.
Different methods can be used to determine the presence or absence of D-dimer in the blood:
- Enzyme-linked immunosorbent assay (ELISA): A labeled antibody is artificially added to check if it binds to the D-dimer protein.
- Latex agglutination: Less labor-intensive but also less sensitive than ELISA. In this method, monoclonal antibodies attached to latex particles bind to D-dimer.
- Red blood cell agglutination: An antibody is used to cause red blood cells to cluster together in the presence of D-dimer.
- Analyzer devices: Modern devices can analyze samples quickly and reliably, significantly speeding up diagnoses. The blood tube is simply placed in the input slot, and the device performs all the analysis steps.
Risks
The D-dimer test does not pose a risk to patients.
Blood extraction may cause dizziness at the time of sampling or bruising at the needle insertion site.
What to Expect from a D-dimer Test
It is recommended to wear clothing that allows easy access to the arm for the blood draw. If a patient has previously experienced dizziness when giving blood samples, they should inform the specialist so the test can be performed while lying down.
A slight pinch is normal when the needle is inserted, but it is a mild discomfort that subsides quickly.
Recommendations include pressing the puncture site with a sterile gauze pad to reduce the risk of bruising and drinking plenty of fluids to help restore blood volume.
The procedure usually takes about five minutes, and normal activities can be resumed immediately.
Results are typically available the day after the blood draw. They should be discussed in a consultation, as their interpretation depends on the patient's specific circumstances and characteristics.
Specialties that Request a D-dimer Test
The D-dimer test is commonly requested in the fields of hematology, genetics, and emergency medicine.
How to prepare
No prior preparation is necessary.
