The purpose of this analysis:
This test is done to help find causes of inappropriate and frequent blood clotting, and to help diagnose antithrombin deficiency.
You are required to perform this analysis in the following cases:
You're asked to have this test two months after you've had a blood clot (thrombin phase), or when you haven't responded as well as you would expect to treatment with heparin as an anticoagulant.
Sample required for analysis:
A sample of blood is drawn from a vein in the arm.
Preparations before performing the analysis:
nothing.
How is the analysis done and what is the doctor looking for?
Antithrombin is a protein produced by the liver that helps regulate the formation of blood clots (meaning it is a natural mild blood thinner). The antithrombin test measures the activity (function) and the amount of antithromin in the blood, and is used to assess the condition of a person who has had many blood clots (clots).
Normally when a blood vessel is injured, the body begins a complex process called hemostasis by forming a blood clot (clot) to prevent further blood loss.
Part of that complex process involves activating several proteins known as clotting factors (coagulation factors) in a series of steps called the coagulation cascade.
Antithrombin helps regulate this process by inhibiting (suppressing) the action of several clotting factors such as thrombin and factors ( Xa , IXa , and XIa ) in order to slow the clotting process and prevent the formation of excessive or inappropriate clots (thrombosis).
People who have excessive clotting as a result of an inherited or acquired antithrombin deficiency are at greater risk of developing blood clots, especially in the deep veins such as the leg veins (deep venous thrombosis - DVT). Genetic deficiency of antithrombin is rare, affecting about 1 in 5,000 people.
For people who have one defective gene and the other normal (the offending genes), they usually start to form the inappropriate blood clot at the age of 20 to 30 years. Very rarely, a person has a genetic defect in two antithrombin genes that leads to severe blood clotting soon after birth.
Acquired antithrombin deficiency may occur at any age. This is associated with many pathological conditions that cause decreased production, increased consumption, or loss of antithrombin. These conditions include: liver disease, severe thrombosis, small disseminated intravascular clots (DIC), blood loss, cancer, and nephrotic syndrome (a disease of the kidneys).
There are two different types of antithrombin deficiency. In the first type: antithrombin works well, but its quantity in the body is insufficient. In the second type: the body produces enough antithrombin, but does not work. The two types can be differentiated and evaluated by performing the following tests:
◊ activity test , to assess antithrombin function.
◊ Antithrombin antigen test , to measure the amount of antithrombin present.
How is the sample needed for this analysis to be collected?
A blood sample is taken from a vein in the arm with a needle (syringe).
Are there any necessary preparations before conducting the analysis to ensure the quality of the sample used?
Usually ; No special preparations required. Note that testing for antithrombin deficiency is not recommended if the person has a disease that affects his antithrombin level (such as a DIC), and/or after the person has received anticoagulant therapy with heparin.
How is this analysis used?
An antithrombin test is primarily ordered, along with other tests in severe thrombosis, to investigate the cause of frequent blood clots (thrombosis). This test evaluates the activity (function) and amount of antithrombin, and helps determine the presence of antithrombin deficiency.
An antithrombin activity test is done first to assess whether the total amount of antithrombin is working normally. If the antithrombin activity is low, then an antithrombin antigen test is done to determine the amount of antithrombin present. These two tests can be used to differentiate between type 1 and type 2 antithrombin deficiency. If a deficiency is detected, the two tests are usually taken again at a later time to confirm the results.
Sometimes an antithrombin test may be used to evaluate people who do not respond as well as they should to heparin therapy. Heparin is an anticoagulant treatment given to people who have a blood clot (thrombosis) or who are at increased risk of inappropriate blood clots (thrombosis). Antithrombin controls the effect of heparin.
Heparin can significantly increase antithrombin activity, thereby inhibiting (suppressing) the formation of blood clots, but people with antithrombin deficiency do not respond to heparin therapy.
When is this analysis required?
A required n antithrombin activity test is ordered along with other tests for severe clotting (such as protein C, protein S, lupus anticoagulant), and when a person has frequent blood clots (thrombosis). A person should only have an antithrombin test after treatment has been completed and the blood clot has dissolved (thrombosis) as both the presence of the clot and treatment influence the test result.
An antithrombin test may also be ordered when a person does not respond as well to heparin as an anticoagulant, when unusually high doses of heparin are required to
anticoagulation.
What are the results of this analysis and what do they mean?
Decreased antithrombin activity and decreased amount of antithrombin antigen suggest the presence of type I antithrombin deficiency. In this case, the activity decreases due to the lack of antithrombin available to participate in the regulation of the clotting process.
Decreased antithrombin activity and a normal amount of antithrombin antigen suggest type 2 antithrombin deficiency. This means that there is enough antithrombin protein, but it is not working as well as it should. In this case, the affected person is at greater risk of developing an inappropriate blood clot (thrombosis).
If antithrombin activity is normal, then the antithrombin antibody test is usually not performed. In this case, antithrombin is working efficiently and the frequent formation of clots (thrombosis) may be due to a cause other than a deficiAntithrombinency of antithrombin.
We can see a temporary or chronic decrease in antithrombin levels associated with conditions that affect the consumption or production of antithrombin, including the following:
- ◊ Small clots spread within the blood vessels (disseminated intravascular coagulation - DIC ), an acute or chronic condition characterized by the consumption of clotting factors; Meaning that the person may bleed and/or clot.
- ◊ A deepvein thrombosis (DVT ) isa thrombus (thrombosis) that usually occurs in a vein deep in the leg.
- ◊ Liver disease.
- ◊ nephrotic syndrome
- ◊ Cases of protein loss.
- ◊ Pulmonary embolism.
- Heparin therapy (temporarily lowers antithrombin levels)
- ◊ Children during the first days of life (about 50% of the antithrombin level in a healthy adult).
- ◊ Estrogen therapy.
๏ High levels of antithrombin are usually not considered a problem.
Are there other things I should know about this analysis?
If a person with antithrombin deficiency has other clotting risks, such as a protein C or S deficiency, a factor V leiden mutation, or birth control pill use, that person's risk of developing a clot Hematuria (the occurrence of thrombosis) increases clearly.
A deficiency of antithrombin can increase the risk of recurrent miscarriage.
People with antithrombin deficiency may need conservative treatment to prevent clotting before surgery.
Concentrations of antithrombin are now available as a drug to temporarily correct acute or chronic antithrombin deficiencies.