Factor VIII Activity and Deficiency

Hemophilia A and Factor VIII deficiency

Hemophilia A is an inherited disorder passed down from male or female parents that causes the clotting protein Factor VIII to be missing or not work properly. This is also referred to as Factor VIII deficiency.

So why is Factor VIII deficiency an issue?

When an injury occurs, a process called hemostasis takes place at the injury site, where your blood forms a clot to stop the bleeding.

Hemostasis takes place in 2 parts:

Primary hemostasis

Platelets (small cell fragments in our blood) move to the area of injury and, with another protein called von Willebrand factor, they form a “platelet plug” to help reduce blood loss.

Graphic depicting how if blood cannot clot properly, hemostasis cannot be restored

Secondary hemostasis

A process called the “clotting cascade” is activated, creating the thrombin molecule, which converts to fibrin and forms a “fibrin mesh” around the platelets at the site of injury. This stabilizes the clot and stops the bleeding.

Factor VIII is a vital protein involved in the hemostasis process. Without enough Factor VIII (ie, if you have Factor VIII deficiency), your body generates less thrombin, blood can't clot properly, and excessive bleeding can occur.

What are factor activity levels?

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.

Because of differing Factor VIII activity levels, every person with hemophilia has unique treatment goals that need to be tailored to their individual needs. That's why it's important to talk to your doctor about managing your hemophilia.

How can Factor VIII activity levels impact lifestyle and activity?

Factor levels can impact lifestyle and activity

You may choose to make lifestyle adjustments or engage in less physical activities to reduce the risk of bleeding and pain associated with hemophilia.

The severity of hemophilia can also impact your ability to be active and take part in physical activities. The lower a person's Factor VIII activity levels are, the lower their level of physical activity tends to be. It's important to speak to your doctor about the best way to manage your hemophilia.

See how different Factor VIII activity levels might impact your ability to perform certain activities:

General guidelines on Factor VIII levels and their impact on the ability to perform activities

Factor VIII activity levels	Impact on physical activity/lifestyle
Normal levels 50% - 150% factor activity	May engage in higher-impact activity without pain (sports, physical jobs, and active days)
Near-normal* ≥40% - <50% factor activity	Near-normal factor activity levels are currently undefined by the World Federation of Hemophilia
Mild hemophilia 5% - <40% factor activity	May engage in higher risk activities (aerobics, Pilates, bicycling, swimming), with some pain Appropriate level of physical activity should be evaluated on a case-by-case basis Supplemental factor is needed for surgery
Moderate hemophilia 1% - 5% factor activity	May engage in limited activity with some pain (walking, golfing, sailing, gardening), with a risk of spontaneous bleeds or microbleeds Requires minor adjustments in lifestyle and the physical activity level can be mild and moderate Supplemental factor is needed for surgery
Severe hemophilia <1% factor activity	A person’s lifestyle is considered “vulnerable,” which means their level of physical activity is low to sedentary There is a high risk of spontaneous bleeds and pain with target joints Supplemental factor is needed for surgery

^*

WFH Guidelines define the upper limit of mild hemophilia as 40% factor activity and the WFH Introduction to Hemophilia defines the normal range as 50% to 150%, which indicates that 40% to 50% would be in-between mild hemophilia and normal, here referred to as “near-normal” levels.

WFH=World Federation of Hemophilia.

Hemophilia A treatment and Factor VIII activity levels

One type of treatment for people with hemophilia A is Factor VIII replacement therapy, which helps to replace missing Factor VIII in your blood due to hemophilia A.

These treatments can be taken regularly, called prophylaxis, to help prevent bleeds. They can also be given on-demand during a bleeding episode to help stop bleeding or perioperatively to help manage bleeding during and around the time of surgery.

The World Health Organization (WHO) and the WFH recommend prophylaxis treatment over on-demand treatment in order to help prevent damage and other complications caused by bleeding.