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What is D-Dimer Test? A D-dimer test can help you determine your body's amount of D-dimer protein. Unless your body produces and breaks down substantial blood clots, D-dimer is generally undetectable at very low levels. A D-Dimer test may help determine whether you have a clotting issue. However, it is not a definitive indicator of the disease.  A D-dimer test can't tell you what type of clotting disorder or the location of the clot in your body. If you have a high D-dimer level in your blood, your physician may conduct some additional imaging techniques or blood tests to make any further diagnosis. What is D-Dimer? When a blood vessel is injured, coagulation or blood clotting occurs as a vital mechanism to avoid excessive bleeding. Platelets and plasma proteins in the blood collaborate to prevent bleeding by creating a clot over the damage. However, if you have any blood clotting disorder, clots can form even when there is no damage, or they do not dissolve after an injury has healed. This is a severe condition as it may cause blood vessel blockage and may even lead to strokes or a heart attack.  Among the many clotting factors and proteins which help to clot, fibrinogen plays a crucial role as it is the main component of the clot, also called the hemostatic plug, along with the platelets at the injured site. However, after the injury is healed, these clots need to be disintegrated naturally to prevent them from growing and causing further problems. This is done by a process called fibrinolysis.  D-dimer is a protein fragment formed after fibrinolysis. Each fibrinogen molecule comprises two sets of α, β, and γ  polypeptide chains that combine to produce a protein with two distal D regions joined by a cross-link to a central E region. After the clot finally dissolves, the D-dimer protein is all that is left floating in the blood. Why do I Need a D-Dimer Test? Your doctor may recommend a D-dimer test if you exhibit symptoms of any blood clotting disorder, such as Pulmonary embolism (PE) When the clot occurs near the arteries of the lungs, it may lead to Pulmonary embolism. It typically occurs when a blood clot lodged in another body organ escapes and moves to the lungs. The most frequent cause of PE is DVT clots. Pulmonary embolism signs and symptoms include: Dyspnea, sudden shortness of breath, or rapid breathing Sharp chest pain that frequently occurs with coughing or movement Back pain More sweating than usual. Rapid heartbeat (tachycardia). Feeling lightheaded or faint. If you are experiencing any symptoms of this clotting condition, it is highly advised to consult a doctor as soon as possible. Deep Vein Thrombosis (DVT). Deep vein thrombosis refers to a condition where a blood clot develops deeps inside the veins. Your arm or one of your legs will typically develop a DVT. Although symptoms are not always present in DVT patients, they may include the following: Unexpected swelling in the arm or leg. Leg pain or discomfort may only occur while you are walking or standing.   Warm sensation in the painful or swollen part of your arm or leg. Having unusually larger veins close to the surface of your skin. If you are experiencing any symptoms of this clotting condition, it is highly advised to consult a doctor as soon as possible. Strokes When the clot blocks the blood supply to the brain, it may lead to Strokes. Some symptoms of a stroke may include: Your face, arm, or leg suddenly becomes numb or weak, particularly on one side of your body. Sudden difficulty understanding, speaking or understanding what is being spoken. Unexpected vision problems in one or both of your eyes. Sudden dizziness, imbalance issues, or poor coordination. Abrupt, debilitating headache with no apparent reason. If you are experiencing any symptoms of this clotting condition, it is highly advised to consult a doctor as soon as possible. Disseminated Intravascular Coagulation (DIC). This is a disorder that results in an excessive number of blood clots. They can develop all over the body, harming various organs and leading to other severe complications. Traumatic injuries, cancer or certain infections are all potential causes of DIC. Some symptoms of Disseminated intravascular coagulation (DIC) may include: gum bleeding vomiting and/or nauseous. Severe abdominal and muscle pain Seizures. Urinating less frequently than usual. If you are experiencing any symptoms of this clotting condition, it is highly advised to consult a doctor as soon as possible. How is D-Dimer Produced? When you get a cut, your body undergoes a sequence of steps to make your blood clump up. It is considered as a normal part of healing, as without a clot, you would keep bleeding and have much more blood loss. However, once the bleeding stops, you do not need the clot any longer as your blood flow gets hampered because of clotting. Thus, your body takes a series of steps in a different direction and breaks the clot down. At the completion of all processes, D-dimer is the leftover product floating around in your blood and is detectable for up to eight hours after formation until the time the kidney clears it out. Thus, a dimer, a single fibrinogen molecule, is considered as one of the important proteins produced by the liver involved in the process of coagulation. In normal conditions, the levels of D-dimer are low whereas high levels of D-dimer in your blood indicates presence of a major clot. Several studies suggest that levels of D-dimer may rise sharply in the case of COVID-19 and is associated with the severity of the disease.  What Happens During a D-Dimer Test? A medical practitioner will use a tiny needle to draw blood from a vein in your arm. A small quantity of blood will be drawn into a test tube or vial once the needle has been inserted. The needle may sting somewhat when it enters or exits your body. Usually, this process takes about four to five minutes. What is The D-Dimer Test Used For? The test is also known as fragment D-dimer test or fibrin degradation fragment test. D-dimer test is commonly used to assess a blood clotting disorder including: Deep vein thrombosis (DVT) : a blood clot situated deep inside a vein. Although these clots normally affect the lower legs, they can also occur in other parts of the body. Pulmonary embolism (PE) : defined as a blockage in an artery in the lungs. The most common cause of PE is loosening and travelling of a blood clot from another part of the body to the lungs. Disseminated intravascular coagulation (DIC) : a condition characterized with the formation of several blood clots that further results in organ damage and other serious complications. The most common causes of DIC are traumatic injuries, infections or cancer. Stroke : the blockage in the blood supply to the brain due to a clot in the arterial system of the brain vasculature. How is The D-Dimer Test Performed? There is no special instruction for you to follow before undergoing D-dimer test. Your health care professional will take a blood sample from a vein in your arm, using a small needle. After the insertion of a needle, a small amount of blood will be collected into a vial. You will feel a little pinch or sting when the needle goes in or out of the skin. Are There any Risks to a D-dimer Test? The risk of having D-Dimer testing is extremely low. However, you can experience a slight sensation, discomfort or bruising where the blood was drawn, but this normally goes away soon.  What Do D-Dimer Test Results Normally Mean? D-dimer tests can help to determine whether you have any underlying clotting disorder. If your blood D-dimer levels are low or normal, you most likely don't have a clotting disease. Different labs may do the test differently, so the normal values of D-dimer test may differ. Your doctor can help you understand more clearly what your results mean. If your D-dimer levels exceed expected, you may have a clotting issue. A D-dimer test, however, cannot identify the type of clotting condition you have or the location of the clot. D-dimer test results are also affected if you are pregnant, have any heart disease, or have undergone any recent surgery. To make a more precise diagnosis, your doctor might use conduct specific further blood tests or imaging procedures, such as: Doppler ultrasound:  Sound waves are used to produce pictures of your veins. Computed tomography (CT) or angiography:  A medical professional injects a particular dye into one of your veins. This aids the appearance of your blood vessels on a certain X-ray machine. Ventilation-Perfusion (V/Q) scan:  A lung VQ scan is an imaging test done to understand your lungs' optimal functioning. This test employs a ventilation (V) scan to evaluate the airflow in your lungs and a perfusion (Q) scan to determine where blood flows through your lungs.  ● If the level of D-dimer is within normal limits, it means you probably don't have a clotting disorder.● If your levels of D-dimer are higher than normal value, you may have a clotting disorder such as PE, DVT, etc.However, it cannot assess where the clot is located or what type of clotting disorder you have. What Does an Elevated D-Dimer in COVID-19 Patients Mean? COVID-19 primarily causes lower respiratory tract infection presenting as cough, fever, dyspnea, and lethargy. However, few cases of the infection can progress into its severe forms like multi-organ failure, DIC, etc. Therefore, it is crucial to discriminate appropriately among infected patients, who are at higher risk of severe infection to treat them early for better prognosis. Raising D-dimer values can help identify people who can be at higher risk of COVID-19 complications. Although the D-dimer test can rule out venous thromboembolism (VTE) in COVID-19 patients, an increased level of D-dimer does not necessarily mean that a patient has VTE. Due to low specificity of D-dimer test, it can be found in several other conditions, such as malignancy, trauma, liver disease, heart disease, sepsis, CPR or recent surgery. Therefore, take help of your doctor to decide your condition in the clinical context. Do not self-medicate or self-diagnose. Caring at home for COVID? Keep a track of your health with the COVID monitoring package. When and How Often Should D-dimer be Measured? There is no strict guideline as to how frequently D-dimer levels should be tested for management and/or monitoring of COVID-19 patients. Follow your doctor’s advice regarding health tests. What is The Outcome of Increased D-dimer in a Patient with COVID-19? Various data suggests that D-dimer greater than 1 μg/ml is strongly associated with in-hospital death of COVID-19 patients.1Similar findings are evident from other research that showed elevated D-dimer at admission and significantly, increasing D-dimer levels (3- to 4-fold over lab reference range) over time are related to poor outcomes such as increased clots, organ failure, etc. In a nutshell A higher level of D-dimer in the body is indicative of presence of clot in the body which is regarded as a dangerous sign in patients with COVID-19. D-dimer in combination with other markers can also assist during the treatment of these patients, as the higher their D-dimer is, higher is the number of clots in the lung and the higher the chances of respiratory failure. Thus, D-Dimer test can be used to indirectly measure the severity of COVID-19 disease and assess its complications at an early stage.