About the Test
Purpose of the test
A fibrinogen test evaluates the level of the protein in the blood and assesses its ability to form blood clots. Fibrinogen testing can be used for diagnosing, monitoring, and screening for a number of conditions that affect blood clotting.
Diagnosing is evaluating you to determine the cause of your symptoms. Measuring fibrinogen levels and assessing the ability of fibrinogen to form clots may be part of the diagnostic process if you experience excessive bleeding or blocked blood flow. Fibrinogen testing is usually performed after initial tests or examinations have ruled out other causes for these symptoms.
Monitoring is periodically performing tests to assess the progression of a disease or your response to treatment. Obtaining a measurement of fibrinogen levels is routinely used if you receive fibrinogen replacement therapy after diagnosing a fibrinogen disorder.
Screening is testing to assess your risk of having a health problem before you develop symptoms. Fibrinogen testing may be ordered for some patients undergoing surgery to evaluate whether they are at a higher risk of excessive bleeding.
What does the test measure?
Fibrinogen testing measures the amount of fibrinogen and assesses whether your fibrinogen can properly form blood clots.
Fibrinogen is a protein made in the liver that circulates in the blood. When an injury occurs and bleeding needs to be stopped, fibrinogen works with other clotting factors and platelets to form a blood clot, which is a mass of blood cells, platelets, and proteins that cluster together to stop bleeding.
During this process, also called coagulation, the body signals another clotting factor called thrombin to bind with fibrinogen. This process creates fibrin, a substance that builds a strong network of microscopic threads that strengthen the blood clot.
Two methods for testing fibrinogen may be used simultaneously:
- Fibrinogen antigen test: This test measures the amount (or quantity) of fibrinogen in a blood sample. It is generally reported in milligrams per deciliter (mg/dL). The fibrinogen antigen test is only needed when the fibrinogen activity test result is abnormal and is therefore typically ordered to help determine if the low activity is due to low quantity or abnormal function of fibrinogen.
- Fibrinogen activity test: This test evaluates how much time it takes for fibrinogen to form a clot. Thrombin is added to a prepared blood sample to stimulate the coagulation process in a test tube. The amount of fibrinogen incorporated into the blood clot is called active (or functional) fibrinogen. Most labs offer a clotting-based activity test (functional) and are also reported as milligrams per deciliter (mg/dL).
When should I get this test?
Fibrinogen testing may be performed when the blood’s clotting ability needs to be evaluated. It is usually prompted if you have signs of abnormal blood clotting like excessive bleeding or a blockage of veins or arteries called thrombosis.
A health care provider may also order a fibrinogen test if the results of a PT or PTT test indicate prolonged clotting times, even if you do not have symptoms.
Fibrinogen testing is ordered to evaluate or diagnose the following conditions:
- Disseminated intravascular coagulation (DIC): This is a serious condition in which excessive amounts of thrombin and fibrin are produced by the body, causing a significant decrease in fibrinogen level. Fibrinogen testing and other blood tests are needed to confirm a diagnosis of DIC.
- Liver diseases: Fibrinogen and most other clotting factors are produced by the liver. Evaluating fibrinogen can assess the health of the liver and the risk of excessive bleeding in some patients.
- Inherited fibrinogen disorders: Certain rare genetic conditions can cause changes in the production and function of fibrinogen that can lead to abnormal bleeding or blood clotting. If you have a personal or family history of fibrinogen disorders, you may have testing to confirm a diagnosis and plan treatment.
- Other acquired fibrinogen disorders: Some types of cancer, autoimmune diseases, and certain medications can disrupt blood clotting. Fibrinogen testing can be used to evaluate how blood clotting is affected by these conditions.
If you have fibrinogen disorders, you may undergo testing to assess your risk for abnormal bleeding or plan treatment with supplemental fibrinogen replacement therapy. Routine fibrinogen testing is especially important if you are pregnant and have a history of abnormal bleeding or previous pregnancy complications due to fibrinogen disorders.
Finding a Fibrinogen Test
How can I get a Fibrinogen test?
Fibrinogen testing is ordered by a licensed health care professional. A blood draw is required and is usually conducted in a clinic, laboratory, or hospital.
Can I take the test at home?
A fibrinogen test can not be conducted at home. Unlike some other coagulation tests, fibrinogen testing can only be conducted in a laboratory with the appropriate equipment.
How much does the test cost?
The cost of fibrinogen testing depends on which type of test is ordered, where the test is performed, and whether you have health insurance coverage. While your health insurance may cover the cost of testing, there may still be costs associated with a copay or deductible.
Check directly with your doctor or insurance provider to learn about the expected costs for fibrinogen testing.
Taking a Fibrinogen Test
Fibrinogen testing is usually performed after the results of other clotting time tests indicate an abnormality that requires further evaluation. A blood draw is ordered by a health care provider for a fibrinogen test and collected in a medical setting.
Before the test
No special preparation is required for a blood draw used for fibrinogen testing. To ensure the accuracy of the test, tell your doctor about any prescription or over-the-counter medications you are taking, especially anticoagulation medications that may affect the results of your fibrinogen levels.
During the test
For fibrinogen tests, a blood sample is taken with a needle inserted into a vein in your arm. There are a number of steps to a blood draw you can expect:
- An alcohol wipe disinfects your arm in the area where the needle will be inserted. This is most often on the inside of the elbow or the top part of the hand.
- A band called a tourniquet is then tied around your upper arm. The tourniquet increases blood pressure, making the vein in your arm more visible and easier to access with the needle.
- A needle is inserted in your vein. This may cause a pinch or a little pain. A separate tube is attached to the needle and filled with blood. Depending on the number of tests prescribed, there may be more than one tube of blood collected.
- After the test tubes are filled and the needle is removed, the test is complete.
After the test
After the blood draw is complete, a bandage or cotton swab will be used to prevent bleeding. You may be instructed to keep this in place for an hour or more.
You may be able to return to normal activities, including driving, once the test is over, though it is common the health care provider will have you stay for 15 minutes or so to observe you for any side effects. Bruising, dizziness, or lightheadedness are possible side effects after any blood draw, which may inhibit your ability to drive or walk.
Contact your doctor if you notice any persistent pain, bleeding, or signs of infection following the test.
Fibrinogen Test Results
Receiving test results
Results of a fibrinogen test may be available within several business days of your blood sample arriving at the laboratory. You may receive a copy of your test results by mail or through an electronic health portal. Your doctor may also call you to discuss the test results or schedule an appointment to review them together.
Interpreting test results
A report of your fibrinogen levels will typically show the amount of active (or functional) fibrinogen in milligrams per deciliter (mg/dL), which will be compared to their reference range. While they can vary from lab to lab, reference ranges help your doctor compare your fibrinogen level to the test results of a large sample of healthy people. The fibrinogen antigen test is less commonly used and not offered by most hospital-based labs.
According to the American Board of Internal Medicine, the reference range for fibrinogen is 200-400 mg/dL. Reference ranges can vary depending on the procedures and equipment in each laboratory, so it is important to ask your doctor to explain your test results.
The results of fibrinogen testing will generally be described as above, below, or within the reference range. However, fibrinogen levels are usually compared with other coagulation tests, like PT and PTT, to properly evaluate the severity and cause of abnormal blood clotting.
Abnormally low levels of fibrinogen can interfere with the creation of blood clots which may result in unexpected and excessive bleeding.
Fibrinogen disorders are associated with abnormal function and/or quantity of fibrinogen. These disorders may be genetic, meaning they are inherited from a parent or acquired as a result of injury or disease. Abnormal fibrinogen can be classified in the following ways:
- Afibrinogenemia is a rare condition in which the body produces no functional fibrinogen.
- Hypofibrinogenemia is a deficiency of fibrinogen, in which activity and antigen levels are chronically below the lower limit of normal reference.
- Dysfibrinogenemia is a dysfunction of the fibrinogen, in which antigen levels may be normal, but the fibrinogen protein does not function normally (decrease in activity).
- Hypodysfibrinogenemia means there is a decrease in the amount of fibrinogen and its ability to form blood clots (decrease in both antigen and activity levels).
Abnormally high fibrinogen levels may occur as part of the body’s normal response to an injury, acute stress, infection, or inflammation. Higher levels of fibrinogen can also occur for other reasons including:
- Tobacco use
- Insulin resistance
Higher levels of fibrinogen also increase the risk of experiencing a stroke or heart disease,
though it is not known whether fibrinogen is a direct cause of these health problems.
The results of your fibrinogen test may be used to confirm a diagnosis or make a treatment plan. Always review your fibrinogen test results with a health care provider who can help you understand how they apply to your personal health situation.
When you review your fibrinogen test results, you may find it helpful to pose some of the following questions to your doctor:
- What type of fibrinogen test did I have, and what are the results?
- Do my test results show that I have a condition that might be affecting my fibrinogen levels?
- Do I need any follow-up tests based on my test result?
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