At a Glance
Why Get Tested?
To help rule out clotting (thrombotic) episodes and to help diagnose conditions related to thrombosis.
When To Get Tested? When you have symptoms of a blood clot or a condition that causes inappropriate blood clots, such as deep vein thrombosis (DVT), pulmonary embolism (PE), or disseminated intravascular coagulation (DIC), and to monitor treatment of DIC and excessive clotting conditions
Sample Required? A blood sample drawn from a vein in your arm.
Test Preparation Needed? None
What is being tested? D-dimer is one of the protein fragments produced when a blood clot gets dissolved in the body. It is normally undetectable or detectable at a very low level unless the body is forming and breaking down blood clots.
Then, its level in the blood can significantly rise. This test detects D-dimer in the blood.
When a blood vessel or tissue is injured and begins to bleed, a process called hemostasis is initiated by the body to create a blood clot to limit and eventually stop the bleeding.
This process produces threads of a protein called fibrin, which crosslink together to form a fibrin net. That net, together with platelets, helps hold the forming blood clot in place at the site of the injury until it heals.
Once the area has had time to heal and the clot is no longer needed, the body uses an enzymecalled plasmin to break the clot (thrombus) into small pieces so that it can be removed.
The fragments of the disintegrating fibrin in the clot are called fibrin degradation products (FDP), which consist of variously sized pieces of crosslinked fibrin.
One of the final fibrin degradation products produced is D-dimer, which can be measured in a blood sample when present. The level of D-dimer in the blood can significantly rise when there is significant formation and breakdown of fibrin clots in the body. For a person who is at low or intermediate risk for blood clotting (thrombosis) and/or thrombotic embolism, the strength of the D-dimer test is that it can be used in a hospital emergency room setting to determine the likelihood of a clot's presence.
A negative D-dimer test (D-dimer level is below a predetermined cut-off threshold) indicates that it is highly unlikely that a thrombus is present.
However, a positive D-dimer test cannot predict whether or not a clot is present. It indicates that further diagnostic procedures are required (e.g., ultrasound, CT angiography). There are several factors and conditions associated with inappropriate blood clot formation.
One of the most common is deep vein thrombosis (DVT), which involves clot formation in veins deep within the body, most frequently in the lower legs. These clots may grow very large and block blood flow in the legs, causing swelling, pain, and tissue damage.
It is possible for a piece of the clot to break off and travel to other parts of the body. This "embolus" can lodge in the lungs, causing a pulmonary embolus or embolism (PE). Pulmonary embolisms from DVT affect more than 300,000 people in the U.S. each year.
While clots most commonly form in the veins of the legs, they may also form in other areas as well. Measurements of D-dimer can be used to help detect clots in any of these sites. For example, clots in coronary arteries are the cause of myocardial infarction (heart attacks). Clots may form on the lining of the heart or its valves, particularly when the heart is beating irregularly (atrial fibrillation) or when the valves are damaged. Clots can also form in large arteries as a result of narrowing and damage from atherosclerosis.
Pieces of such clots may break off and cause an embolus that blocks an artery in another organ, such as the brain (causing a stroke) or the kidneys. Measurements of D-dimer may also be ordered, along with other tests, to help diagnose disseminated intravascular coagulation (DIC). DIC is a condition in which clotting factors are activated and then used up throughout the body. This creates numerous tiny blood clots and at the same time leaves the affected person vulnerable to excessive bleeding.
It is a complex, sometimes life-threatening condition that can arise from a variety of situations, including some surgical procedures, sepsis, poisonous snake bites, liver disease, and after childbirth. Steps are taken to support the affected person while the underlying condition resolves. The D-dimer level will typically be very elevated in DIC.
Be Safe !
source: Labtestsonline.org