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In people with clotting disorders (thrombophilia), the blood clots more easily than it should, which can cause clots to form inside the blood vessels. Bleeding disorders such as hemophilia and von Willebrand disease prevent the blood from clotting normally, leading to an increased risk of bleeding. Around 3% to 8% of the Caucasian populations in Europe and the United States have a copy of the factor V Leiden mutation, which is the most common hereditary form of thrombophilia. The CDC reports that von Willebrand affects about 1% of the general population of the United States. Approximately 20,000 Americans have hemophilia.
This guide provides an overview of the fibrinogen blood test. It also includes detailed information about hemophilia, von Willebrand disease, and factor V Leiden.
The purpose of the fibrinogen blood test is to determine if there’s too much or too little fibrinogen in an individual’s blood. Too much fibrinogen is a sign that an individual has an increased risk of developing blood clots that could break off and travel to the lungs or cause a stroke. A lower-than-normal fibrinogen level may indicate the presence of an inherited bleeding disorder. Because fibrinogen and other clotting factors are produced by the liver, low fibrinogen levels are also associated with liver disease.
The fibrinogen test is usually ordered when someone has signs of abnormal clotting, such as excessive bleeding after a minor injury, a history of blood clots in the deep veins of the thigh or lower leg, bleeding gums, or easy bruising. It may also be ordered if an individual has symptoms of liver disease or a prolonged prothrombin time, which is a measurement of how long it takes the plasma in a person’s blood to clot.
The fibrinogen test is performed on a sample of blood.
No special preparation is required for the fibrinogen test.
Factor V Leiden is a genetic mutation that makes it more likely that a person’s blood will form abnormal clots inside the vessels. The mutation affects the F5 gene, which contains instructions for producing factor V, an essential component of the clotting process. In people with the factor V Leiden mutation, factor V circulates in the blood longer than it should, increasing the risk of clot formation. An individual with this mutation on both copies of the F5 gene has a higher risk of blood clots than an individual with the factor V Leiden mutation on just one copy of the F5 gene.
Not all people with the factor V Leiden mutation develop blood clots in their vessels. Those who do may develop deep vein thrombosis at an early age. Deep vein thrombosis (DVT) is a condition that develops when a clot forms in one of the veins deep inside the body. Another sign of factor V Leiden is having a pulmonary embolism (PE) before the age of 50. PE is a serious condition in which a blood clot breaks loose and travels to the lungs, blocking one of the pulmonary arteries. People with factor V Leiden mutations may also develop blood clots in the brain or liver, have a family history of blood clots, have a history of losing pregnancies in the second or third trimester, or develop DVT during pregnancy or shortly after giving birth.
In people with factor V Leiden, the risk of developing a blood clot depends on several factors. Women who take birth control pills or hormone replacement therapy have a higher risk of blood clots than women who don’t. The risk of clotting is also higher in someone who has other genetic mutations related to blood clotting than it is in someone who only has the factor V Leiden mutation.
Another important component of the clotting process is the von Willebrand factor (VWF), a protein that helps platelets stick together. When platelets stick together, they form a clot, preventing excessive blood loss after an injury. Some people with von Willebrand disease have a VWF deficiency, while others have abnormal VWF; both groups have a heightened risk of bleeding during dental procedures, after surgery, or any time an injury occurs.
Type 1 von Willebrand disease is characterized by a VWF deficiency. Approximately 85% of people with von Willebrand disease have this type, which is the mildest form of the condition. Type 2 is more severe than type 1, and it affects approximately 12% of people with von Willebrand disease. People with type 2 von Willebrand disease produce normal amounts of VWF, but the VFW doesn’t work properly. Type 3, the most severe form, affects just 3% of people with von Willebrand disease.
In people with von Willebrand disease, symptoms may be mild or severe. Mild symptoms include easy bruising, frequent nosebleeds, and excessive bleeding following an injury or surgical procedure. Nosebleeds may last for longer than 10 minutes; some people even need to have the blood vessels in their noses cauterized — sealed with an electrical current — to prevent excessive bleeding. When bruises form, they may have raised lumps or take several weeks to disappear. In some people, particularly those with type 3 von Willebrand disease, blood can leak into the joints or the vital organs, causing life-threatening complications.
Hemophilia is classified as either hemophilia A or hemophilia B. Both types of hemophilia have the same symptoms, but they have different causes. Hemophilia A develops when an individual has a mutation in the F8 gene, which contains instructions for producing clotting factor VIII. Hemophilia B develops due to mutations in the F9 gene, which contains instructions for producing clotting factor IX. Both factors are essential for normal blood clotting. Men are more likely to have hemophilia than women due to genetic differences between the sexes. The F8 and F9 genes are both found on the X chromosome. While women have two X chromosomes, men only have one. Thus, if a woman has one normal gene and one gene with a mutation, the normal gene will produce factor VIII or IX. In men with F8 and F9 mutations, there is no normal gene, resulting in a lack of clotting factor VIII or IX.
People with mild cases of hemophilia may not know they have it until they experience excessive bleeding after some type of tissue trauma. For example, an individual may not find out he has hemophilia unless he bleeds excessively during a surgical procedure. People with hemophilia may also experience joint swelling or joint pain. More severe cases of hemophilia produce symptoms such as spontaneous bleeding and bleeding into the internal organs.
The fibrinogen test is performed on the plasma portion of an individual’s blood. Before the plasma can be analyzed, the individual must provide a blood sample. This sample can be collected in a hospital, outpatient laboratory, urgent-care clinic, or other medical setting. Once the blood sample has been collected, laboratory personnel run it through a centrifuge for several minutes. A centrifuge is a piece of medical equipment that separates the plasma from other blood components. After the plasma has been isolated, laboratory personnel use a method known as electromagnetic clot detection to determine how much fibrinogen is present.
The treatment for factor V Leiden depends on whether an individual has ever had DVT or a pulmonary embolism. People without a history of these conditions are usually given information about how to reduce the risk of blood clots. For example, a woman with factor V Leiden may be advised not to take oral contraceptives. An individual who has had a DVT or pulmonary embolism may have to take blood thinners to prevent clots from forming in the blood vessels. Because pregnancy increases the risk for blood clots in women with factor V Leiden, a pregnant woman may or may not need to take blood thinners during her pregnancy. It depends on whether she has a family history of blood clots or plans to deliver via Cesarean section.
One of the most common treatments for von Willebrand disease is desmopressin acetate, a medication that stimulates the release of VWF. Some people with von Willebrand disease need factor concentrates, which either correct a VWF deficiency or replace defective VFW with normal VFW. Depending on an individual’s medical history and risk factors, other treatments may be used to reduce the risk of severe bleeding. For example, if factor concentrates are not effective, platelet concentrates may be administered to help stop bleeding. Individuals with rectal bleeding or bleeding in the intestines may take antifibrinolytic agents, which prevent clots from breaking down.
People with hemophilia A and hemophilia B may also need to be treated with factor concentrates. In cases of hemophilia A, factor concentrates are used to replace the missing factor VIII; factor concentrates replace the missing factor IX in people with hemophilia B. Some factor concentrates are derived from human plasma; these products are known as plasma-derived factor concentrates. Another type of factor concentrate, known as a recombinant factor concentrate, is produced via genetic engineering. Both types of factor concentrates are effective for replacing missing clotting factors, but recombinant factor concentrates are slightly safer because they’re not derived from human blood.
Desmopressin acetate can also be used to treat hemophilia A, as it stimulates the release of factor VIII from the body’s tissues. Epsilon aminocaproic acid prevents clots from breaking down. Some people with hemophilia take this drug after having tooth extractions or other dental procedures. Emicizumab has the same functions as factor VIII, so it can also be used to treat people with hemophilia A.
A normal fibrinogen level ranges from 200 to 420 milligrams per deciliter (mg/dL).
Low fibrinogen levels are associated with hereditary bleeding disorders, excessive bleeding, and a condition called disseminated intravascular coagulation. DIC causes small blood clots to form throughout the body, depleting fibrinogen and other clotting factors. In people with DIC, fibrinogen levels may remain normal at first, making the fibrinogen blood test most helpful for diagnosing advanced cases of the condition. A low fibrinogen level is also a potential sign of liver disease.
A high fibrinogen level indicates that an individual has an elevated risk of developing blood clots in the vessels. High fibrinogen levels are also associated with pregnancy, heart attack, cancer, stroke, rheumatoid arthritis, infections, and high levels of inflammation.
An individual with an abnormal fibrinogen level may need other blood tests to check for bleeding or clotting disorders, cancer, high levels of inflammation, or liver disease. The comprehensive metabolic panel is useful for diagnosing liver disease, as it measures the amounts of several liver enzymes in the blood. If these enzymes are elevated, it could indicate that the liver is inflamed or damaged. The comprehensive metabolic panel also helps identify mineral imbalances and diagnose problems with the kidneys. A complete blood count determines how many red blood cells, platelets, and white blood cells are in an individual’s blood. This test can be useful for diagnosing cancer and infections. The erythrocyte sedimentation rate and C-reactive protein blood tests are both used to detect inflammation.
In some cases, a high fibrinogen level indicates that an individual has an increased risk for developing heart disease. People with a high risk of heart disease may have to make lifestyle changes to reduce the risk of heart attack and stroke. These lifestyle changes include quitting tobacco, losing excess weight, following a diet that is low in saturated fat and cholesterol, and getting regular aerobic exercise. Some people with a high risk of heart disease may also have to take medications to lower their blood pressure or cholesterol levels.
For more information about factor V Leiden, von Willebrand disease, and hemophilia, along with the tests used to diagnose and manage these conditions, visit the following resources.
|National Hemophilia Foundation||www.hemophilia.org||Access educational materials on hemophilia and other bleeding disorders.|
|Centers for Disease Control and Prevention||www.cdc.gov||The CDC provides a list of resources for patients with von Willebrand disease.|
|Foundation for Women & Girls with Blood Disorders||www.fwgbd.org||Learn more about thrombophilia and how it affects women.|
|National Blood Clot Alliance||www.stoptheclot.org||The National Blood Clot Alliance explains the dangers of blood clots.|
|MedlinePlus||www.medlineplus.gov||Learn more about the blood tests used in the diagnosis and management of bleeding and clotting disorders.|