Summary

• Clotting (coagulation) factors help your blood clot.
• They are activated when you have an injury.
• You need enough of all the factors working one after the other in a specific order for your blood to clot properly.
• PT/INR and APTT are tests that measure how long it takes your blood to clot.
• If you have problems with bleeding or clotting or if you have had results from the PT/INR or APTT tests that were abnormal you may be asked to have a coagulation factor test to gain more information.

What is clotting factor testing?

Specific clotting factor tests are used to help investigate bleeding or blood clotting disorders. They are usually ordered:

• after you have had other blood tests, such as a PT/INR and/or an APTT test, that have given abnormal results.
• if you have a family health history of clotting disorders - some coagulation factor problems are inherited, although this is rare.
• if you have a health condition such as liver disease that could be affecting your ability to make coagulation factors.
• to monitor your body’s ability to clot if you are known to have problems with bleeding and clotting and you are taking medication that lowers the risk of blood clots.

How blood clotting works

• Clotting is a normal part of healing. When you have an injury, and a blood vessel starts to bleed, your body triggers a series of interactions to make a blood clot to stop the bleeding.
• Platelets (thrombocytes) are tiny plate-shaped cells that circulate in your blood. When they sense damage to a blood vessel, they travel to the area where they change their shape by growing long tentacles, become sticky and clump together.
• When activated, platelets release chemicals to attract more platelets and other cells, setting off the next step. This is the coagulation cascade.
• Proteins called coagulation (clotting) factors are activated one after the other, then threads of a protein called fibrin are produced. These threads stick to each other to form a fibrin net that catches the sticky platelets and hold them together to form a clot.
• Once a clot is formed, other substances are activated to slow the clotting process. As the tissue heals and you don't need the clot anymore, the fibrin strands dissolve.

Clotting factors

Clotting factors are proteins that are made mostly in your liver. They have names, such as fibrinogen and prothrombin. Each clotting factor also has a number, a Roman numeral, such as clotting factor I or II or VIII.

The coagulation cascade is the name given to the series of steps by which clotting factors are activated to make a blood clot.

There are three main pathways through which clotting factors are activated. These are called the intrinsic, extrinsic, and common pathways. These are not real pathways inside the body but naming them in this way helps scientists understand and describe how bleeding occurs.

Clotting factors are referred to as belonging to two pathways: 

• The extrinsic pathway 
• The intrinsic pathway 

These join together for the final stage of the clotting process in: 

• The common pathway

Each coagulation factor plays its own role in clot formation. Each must be working properly and there must be enough of each factor for normal clotting to occur.

If there is not enough of one or more of the coagulation factors, or if the factors are functioning abnormally, then stable clot formation will not take place. This can lead to excessive bleeding and/or clotting.

Also, if there are too few platelets, or if platelets aren’t functioning properly, you may bleed more easily. Too many platelets can increase the risk of blood clots that can block blood vessels and cause deep vein thrombosis, pulmonary embolus, heart attacks or stroke.

Why get tested?

Acquired bleeding and clotting disorders – having an underlying health condition that affects clotting

A range of health conditions can affect clotting. These are called acquired conditions. They usually involves two or more factors. Acquired conditions may involve multiple factor deficiencies that must be identified and treated.

• Severe liver disease 
• Lack of vitamin K
• Cancer and cancer treatments
• Autoimmune disorders
• Preeclampsia 
• Heparin-induced thrombocytopenia
• Myeloproliferative disorders such as polycythaemia vera
• HIV or other infections 
• Recent trauma or surgery
• Kidney disease (affects platelets)
• Antibodies to specific clotting factors
• Anti-platelet drugs (aspirin) and anticoagulants (warfarin)

Inherited bleeding and clotting disorders

Inherited clotting disorders are rare and usually involve only one coagulation factor, which may be partly or completely deficient or not functioning properly. Factor testing may be done especially when bleeding episodes begin early in life or when a close relative has an inherited factor deficiency. If an inherited deficiency is diagnosed, other family members may also be tested.

Haemophilia A and B are the most common inherited disorders. von Willebrand’s disease (vWD) is another relatively common inherited bleeding disorder. vWD is due to a deficiency in von Willebrand factor which is responsible for helping platelets stick to the blood vessel wall and to each other. While von Willebrand factor testing may be ordered along with coagulation factor tests, it is usually considered separately.

Monitoring medication

Coagulation factors can also be monitored to make sure anticoagulant medications are working as they should.  Factors may also be measured to see if their function improves when the underlying condition that is causing the deficiency is treated.  

Having the test

Sample

Blood.

Preparation

None.

Your results

Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.

Initial coagulation profile tests will show whether your clotting system is functioning normally.

• The PT test can show if there are problems in the extrinsic pathway. 
• The APTT test can show if there are problems in the intrinsic pathway. 
• If one or both are abnormal, the suspected clotting factor problems they suggest can then be tested individually.  
• You may need to have tests for one or more factors at a time.

The coagulation factors may be measured in terms of concentration and activity. Variations can occur with both types of measurement.

Normal coagulation factor levels and activity usually mean normal clotting function. If the amount of a factor present is enough but the activity level is low, it may mean that the factor is not working properly.

• If the APTT is abnormal and the PT is normal, you may have deficiencies of factors VIII, IX, XI, or XII.
• If the APTT is normal and the PT is prolonged (takes a longer time to clot), you may have a deficiency of factors VII.
• If both PT and APTT are abnormal, you may have deficiencies in the common pathway (I, II, V, X) or deficiencies in multiple factors.
• Low levels and/or activity of one or more coagulation factor usually means impaired clotting ability.
• If you are experiencing acute illness, stress, inflammation or pregnancy you may have high levels of several factors. In general, this is not thought to be associated with diseases. However, in some cases (such as elevated fibrinogen) it may increase the risk of developing blood clots.
• If the factor activity is normal, but the amount of factor present is low, it may mean that there is something interfering with factor production or that something is stopping the factor from working properly.

Coagulation factor levels can be temporarily affected by many conditions, such as increased stress, infection, or increased oestrogen levels due to the menstrual cycle, oral contraceptive therapy or pregnancy.

Reference intervals

Your results will be compared to reference intervals (sometimes called a normal range). 

• Reference intervals are the range of results expected in most healthy people of the same age and sex.
• Your results may be flagged high or low if they sit outside this range.
• Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong.

Blood test results must be interpreted with an understanding of your own symptoms and clinical situation.  For this reason, your results are best interpreted by your own doctor.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking, including Chinese medicines or supplements. Find out if you need to fast or stop any foods, medications or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record.

You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.