Coagulation Factors

Coagulation factor testing is performed to determine if a person has enough coagulation activity to control the blood clotting process. It is used by healthcare practitioners to determine if the level of a coagulation factor is low or absent (below the detectable limit) or if it is too high. Low coagulation factor activity is associated with reduced clot formation and excess bleeding. High coagulation factor activity can be associated with too much clot formation (thrombosis) and blockade in the circulatory system (thromboembolism).

One or more coagulation factor activity tests may be ordered to evaluate the function of specific factors. If a test result shows reduced activity, then an antigen test may be ordered as a follow-up test. This is occasionally done to determine if the low activity is due to a decreased quantity of a normal coagulation factor or due to a coagulation factor that does not function normally.

Coagulation factor testing may sometimes be ordered if a person has a family history of bleeding.

Coagulation factor tests are typically ordered when someone has a prolonged prothrombin time (PT) and/or partial thromboplastin time (PTT). The PT and PTT tests are used as screening tools to determine if someone has a coagulation problem or as part of an investigative workup when someone has signs and symptoms of a bleeding disorder, such as unexplained bruising, bleeding gums, excess bleeding from small cuts, or frequent nose bleeds.

Factor activity may be measured when a healthcare practitioner suspects that a patient has an acquired condition that is causing bleeding, such as vitamin K deficiency or liver disease.

Factor testing may be done when a healthcare practitioner suspects that a patient has an inherited coagulation factor deficiency such as Von Willebrand disease or hemophilia A, especially when bleeding episodes begin early in life or when a close relative has an inherited factor deficiency. When an inherited deficiency is suspected, other family members may also be tested to help confirm the person's diagnosis and to establish whether they may be carriers of the condition or have the deficiency themselves (in an asymptomatic or less severe form).

Sometimes factor testing may be done for a person with a known deficiency to monitor the factor deficiency and to evaluate the effectiveness of treatment.

Occasionally, factor testing is ordered when someone has an unexplained blood clot (thrombosis) to determine whether abnormally high factor activity is the underlying cause (e.g., elevated factor VIII activity is associated with excess clotting).

Normal coagulation factor activity usually means normal clotting function. Low activity of one or more coagulation factors usually means impaired clotting ability. Each coagulation factor must be present in sufficient quantity in order for normal clotting to occur, but the level required is different for each factor. Results are frequently reported as a percentage with 100% being normal. For example, a factor VIII that is 30% would be considered abnormally low.

Deficiencies in coagulation factors can develop in several different ways. They may be acquired as part of other diseases or inherited. Deficiencies vary in severity and may be permanent or temporary.

If more than one clotting factor is decreased, it is usually due to an acquired condition. Acquired deficiencies are rare and may be caused by chronic or acute conditions, including:

• Excess blood clotting that uses up coagulation factor (e.g., disseminated intravascular coagulation)
• Liver disease (i.e., cirrhosis)
• Some cancers
• Exposure to snake venom
• Fat malabsorption
• Vitamin K deficiency
• Anticoagulation therapy (warfarin)
• Massive blood transfusions (e.g., transfuse only red blood cell units)

Inherited coagulation factor deficiencies are rare. They tend to involve only one factor, which may be reduced or absent (below the detectable limit).

Hemophilia A and B are the most common examples of inherited disorders. They are X-linked deficiencies of factors VIII and IX that occur almost exclusively in men. Women are more likely to be asymptomatic carriers of these genetic traits or have mild bleeding. Other inherited factor deficiencies, not associated with the X chromosome, are found equally in both men and women.

The severity of symptoms associated with an inherited factor deficiency depends on the factor involved, its functionality, and the amount of factor available. Symptoms may vary from episode to episode, ranging from excessive bleeding after dental procedures to severe recurrent bleeding into joints or muscles.

Individuals with a modest reduction in coagulation factor activity may have few symptoms and may discover their deficiency in adulthood, after a surgical procedure or trauma or during screening that includes a prothrombin time (PT) or partial thromboplastin time (PTT) test.

Individuals with severe factor deficiencies may have their first bleeding episode very early; for example, a male infant with a deficiency of Factor VIII, IX, or XIII may bleed excessively after circumcision.

Elevated levels of several factors are seen in situations of acute illness, stress, or inflammation. Some people have persistent elevations of factor VIII that may be associated with an increased risk of venous thrombosis.

For both inherited and acquired factor deficiencies, the missing factor(s), once identified, can be replaced as needed. This may be done with a transfusion of fresh frozen plasma (FFP), which contains various coagulation factors, with a concentrated cryoprecipitate, or with replacement factors (some are available commercially, such as recombinant factor VIII). These treatments may be used during a bleeding episode or as a preventive measure to prevent excessive bleeding during an upcoming surgery or other invasive procedure.