086264: Factor VIII Activity | Labcorp (2024)

Factor VIII is a large glycoprotein cofactor (320 kilodaltons) that is produced mainly in hepatocytes, but also to some extent by liver macrophages, megakaryocytes, and endothelial cells.6,10 Factor VIII circulates in the plasma bound to von Willebrand factor (vWF) at a concentration of approximately 0.1 mg/mL.10 The plasma half-life of factor VIII is short at about 8 to 10 hours.10 Factor VIII deficiency should be suspected when a patient with excessive bleeding has a normal protime (PT) and an extended activated partial thromboplastin time (aPTT).

Hemophilia A, or classic hemophilia, occurs as the result of congenital deficiency of factor VIII.6,11 Clinical features of hemophilia A are the same as for hemophilia B which is caused by factor IX deficiency (see Factor IX Activity [086298]). Hemophilia A is the second most common inherited bleeding abnormality (second only to von Willebrand disease), occurring in approximately 1 of every 5000 live male births.6,11 Hemophilia A accounts for approximately 85% of all hemophilia cases.11 This condition is transmitted as an X chromosome-linked hereditary disorder.11 The majority of cases occur in men whose mothers are carriers of the genetic defect. About 30% of factor VIII deficiencies arise in men as spontaneous mutations.6,11 The prevalence of hemophilia A is equal in all ethnic groups.6,11 Female carriers of hemophilia A may rarely present with excessive bleeding.6 Hemophilia symptoms can also occur in female carriers who have a high degree of lyonization of the factor VIII alleles.11 Females with Turner syndrome karyotype XO, can also be symptomatic.11

The severity of hemophilia A can be defined by the level of factor VIII activity.7,11 Severe hemophilia, which represents approximately half the cases, is associated with a factor VIII level <1%. About 10% of cases are moderate with factor VIII levels of 1% to 5% and the remaining 30% to 40% of hemophiliacs have the mild condition with factor VIII levels above >5%.

Approximately 45% of cases of severe hemophilia A occur as the result of a genetic inversion of intron 22 of the factor VIII gene locus.7,11,12 This genetic mutation results in the production of a protein that has no functional or immunologic factor VIII activity.11 Numerous deletions, point mutations, and missense mutations have also been implicated in hemophilia A.7,11 Family studies combined with genetic testing can determine if at-risk women are carriers for a hemophilia A mutation.11 Factor VIII activity levels should not be used as the method of determining carrier status because a number of clinical conditions including pregnancy, infection, or inflammation can affect activity levels.11

Patients with hemophilia A can present with any number of bleeding manifestations.6,11 Often, infants with severe hemophilia are first diagnosed during the neonatal period because of excessive bleeding after circumcision or due to cord necrosis.11 Hemophilic infants also frequently suffer from intracranial hemorrhage or scalp hematomas. Spontaneous hemarthroses, a common symptom of hemophilias, typically do not occur until the child starts walking.7,11 Hematomas can often be observed at the sites of intramuscular injections for vaccination or medication. The most common sites of spontaneous bleeding in patients with severe hemophilia involve the joints and muscles. Recurrent bleeding leads to chronic muscle injury and degeneration of the joint tissue.6,11 Gastrointestinal bleeding can occur in approximately 10% of hemophiliacs.11 Males with mild-to-moderate hemophilia and female carries may have an increased bleeding tendency, especially following surgery or trauma.7

Most individuals with von Willebrand disease will have decreased factor VIII levels because the von Willebrand factor (vWF) is the carrier protein for factor VIII in plasma.6,11 Individuals with von Willebrand disease type 2 Normandy will have normal to slightly low vWF ristocetin cofactor activity and von Willebrand factor antigen and low factor VIII levels due to defective binding of factor VIII to the variant vWF molecule.11

Factor VIII levels are elevated at birth and increase during pregnancy.6 Factor VIII is an acute phase reactant with levels that rise during periods of acute stress, following surgery, and in inflammatory conditions.6 Levels can also increase as the result of strenuous exercise or the administration of several drugs including epinephrine, DDAVP, or estrogen (for birth control or hormone replacement therapy). Factor VIII levels can be elevated in a number of clinical conditions including carcinoma, leukemia, liver disease, renal disease, hemolytic anemia, diabetes mellitus, deep vein thrombosis, and myocardial infarction.6

Persistent elevation of factor VIII above 150% is associated with an increased risk for venous thrombosis of more than fivefold.10,13 Elevated factor VIII is also associated with an increased risk for recurrence of venous thromboembolism. Risk is graded such that the higher the factor VIII activity, the higher the risk.14 The basis for this increased risk is not well understood as genetic studies of the factor VIII and von Willebrand factor genes failed to identify a genetic basis for this increased risk.10 Values >150% are observed in 20% to 25% of individuals with venous thrombosis or thromboembolism in the absence of other known causes of factor VIII elevation.13

A syndrome of combined factor VIII and V deficiencies has been described in over 60 families in and around the Mediterranean basin.15

Hemophilia A patients receiving replacement products can develop inhibitors to factor VIII due to the production of alloantibodies.6,8 Acquired hemophilia caused by the development of autoantibodies to factor VIII can also occur.9 This rare condition (1 in 1,000,000 individuals) can following pregnancy and in elderly individual with autoimmune disorders. In this life-threatening condition, patients have bleeding symptoms similar to those seen in severe congenital hemophilia A.

086264: Factor VIII Activity | Labcorp (2024)


What is the normal range for factor VIII activity? ›

Normal ranges for factor VIII levels are 50% to 150%. If your factor VIII activity level is less than 50%, you may have hemophilia A, but how severe your risk of bleeding is depends on what percentage you have.

What does a high factor VIII activity mean? ›

High levels of FVIII are an even stronger risk factor for repeat blood clots. The likelihood of a second clotting event within two years of the first clot was found to be 37% in people with a high FVIII level versus 5% among persons with a lower FVIII level.

What is factor VIII activity activity? ›

What Is a Factor VIII Activity Test? Proteins called clotting factors help blood clot properly and help prevent too much bleeding. A factor VIII activity blood test lets doctors see how well a protein called factor VIII is working. The body's clotting factors are numbered using the Roman numerals I through XIII.

What is the normal range for von Willebrand factor activity? ›

The normal range of VWF:Ag value varies with each laboratory, but is generally accepted to be between 50 and 200 IU/dL. Levels below 50 are considered to be low, although the degree to which these levels may be depressed on a population-wide basis generates controversy in the diagnosis of VWD.

What is abnormal factor VIII? ›

Summary. Hemophilia A is characterized by deficiency in factor VIII clotting activity that results in prolonged bleeding after injuries, tooth extractions, or surgery, and delayed or recurrent bleeding prior to complete wound healing.

What factor VIII level is typical for mild hemophilia A? ›

Based on the amount of coagulation FVIII present, it is therefore possible to distinguish haemophilia into: Mild: the amount of FVIII is between 6% and 40% of normal. Spontaneous bleeding is rare in this case and is often the result of trauma or surgery.

How do you treat elevated factor VIII activity? ›

Treatment of Elevated Factor VIII, IX, and XI Levels

Direct oral anticoagulants and vitamin K antagonists are effective for treatment of patients with elevated factor VIII, IX and XI levels with a venous thromboembolism (1).

How is factor VIII activity measured? ›

The one-stage activated partial thromboplastin time (aPTT)-based clotting assay is the most commonly used method worldwide for testing FVIII or FIX activities. Alternatively, FVIII and FIX chromogenic substrate assays, which assess the activation of factor X, are available in some specialized laboratories.

What is factor VIII inflammation? ›

Factor VIII is an acute-phase factor that rises two- to fourfold during an inflammatory response to infection, cancer, surgery, trauma, and other stimuli. Factor VIII levels increase with age. Some individuals show a persistent elevation of factor VIII activity in the absence of an acute-phase response.

Can factor VIII levels change? ›

The amount of Factor VIII in your blood is called your "factor activity level" Everyone's factor levels are different, and they can change over someone's lifetime. However, people with lower factor levels have a greater bleed risk, and people with higher factor levels are better protected from bleeds.

Why is factor VIII important? ›

The F8 gene provides instructions for making a protein called coagulation factor VIII. Coagulation factors are a group of related proteins that are essential for the formation of blood clots. After an injury, clots protect the body by sealing off damaged blood vessels and preventing further blood loss.

What is factor VIII overactivity? ›

Hyperactivity of coagulation factor VIII (fVIII) marks hypercoagulation. FVIII enhances activity of factor IX and their combination activates factor X, which is of primary importance in prothrombin transformation into thrombin, on the phospholipid membrane.

What level of factor VIII is von Willebrand disease? ›

In type 1 VWD, the FVIII levels in plasma are slightly higher than VWF and may fall in the normal range. In type 2 individuals, other than type 2N, FVIII levels are 2-3 times higher than VWF. However, it is decreased in type 2N individuals. In type 3 individuals, the plasma levels of FVIII are below 10 IU/dl[50,51].

How to read Von Willebrand test results? ›

VWF antigen levels usually range from 50-200 IU/dL (50-200% of normal). Levels <50 IU/dL are considered low and are diagnostic of VWD in a patient with abnormal bleeding, 3 and levels <30 IU/dL (30% of normal) are considered diagnostic for VWD regardless of bleeding history.

What are the lab values for von Willebrand disease? ›

Normal RCoF values are 50-200 IU/dL. A level below 30 IU/dL is considered definitive for vWD, although levels of 30-50 IU/dL may be found in some patients with type 1 or 2 vWD. Newer vWF activity assays use gain-of-function GPIbα mutants that bind vWF without the need for ristocetin.

What is a normal factor VII level? ›

The normal value is 50% to 200% of the laboratory control or reference value. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results.

What is a normal clotting factor level? ›

It is measured prior to receiving any treatment and is used because it best represents a person's inherent clotting factor activity. Results are reported as a percentage of a "normal" level of clotting factor. The average normal factor level is 100%, with the normal range generally defined as 50% to 150%.

What is the range for factor VIII inhibitor? ›

The Factor VIII inhibitor level in a normal individual is less than 0.5 Bethesda unit. Critical value: greater than 0.5 Bethesda unit (if no prior inhibitor present). * Reference ranges may change over time. Please refer to the original patient report when evaluating results.

What is a normal factor 8 level U mL? ›

For FVIII assays, levels are compared with a normal pooled-plasma standard, which is designated as having 100% activity or the equivalent of FVIII U/mL. Normal values are 50-150%. Values in hemophilia are as follows: Mild: > 5%

Top Articles
Latest Posts
Article information

Author: Nathanael Baumbach

Last Updated:

Views: 5775

Rating: 4.4 / 5 (75 voted)

Reviews: 82% of readers found this page helpful

Author information

Name: Nathanael Baumbach

Birthday: 1998-12-02

Address: Apt. 829 751 Glover View, West Orlando, IN 22436

Phone: +901025288581

Job: Internal IT Coordinator

Hobby: Gunsmithing, Motor sports, Flying, Skiing, Hooping, Lego building, Ice skating

Introduction: My name is Nathanael Baumbach, I am a fantastic, nice, victorious, brave, healthy, cute, glorious person who loves writing and wants to share my knowledge and understanding with you.