Von Willebrand factor
A protein that does two jobs in clotting: it helps platelets stick to the wall of an injured blood vessel, and it carries and protects factor VIII in the blood. A low level or a faulty version causes von Willebrand disease, the commonest inherited bleeding disorder.
What it measures
Von Willebrand factor is a large protein central to the first stage of forming a clot. When a blood vessel is injured, it acts like a glue that helps platelets stick to the damaged wall and to each other, plugging the gap. It has a second, separate role: it binds, carries and protects clotting factor VIII in the bloodstream, so a shortage of von Willebrand factor also drops factor VIII. Testing usually measures both how much is present (the antigen) and how well it works (its activity), because in some people the amount is normal but the protein is faulty. Its main clinical use is diagnosing von Willebrand disease — the commonest inherited bleeding disorder — where too little, or a poorly working, von Willebrand factor causes a bleeding tendency: easy bruising, frequent or prolonged nosebleeds, heavy menstrual periods, and prolonged bleeding after dental work, surgery or childbirth. There are different types, from mild and common to rarer, more severe forms. Von Willebrand factor also rises as an acute-phase reactant with inflammation, illness, pregnancy, exercise and stress, which can temporarily mask a mild deficiency, so testing is sometimes repeated for a reliable result.
What a high value can mean
- Acute-phase rise — inflammation, infection, illness, surgery, pregnancy, exercise and stress raise it temporarily.
- A masked mild deficiency — a temporary rise can hide a mild von Willebrand disease, so testing may be repeated.
- A marker of blood-vessel (endothelial) activation — studied in some conditions, but not a routine clinical use.
- Blood group — group O tends to have lower, non-O groups higher levels.
What a low value can mean
- Von Willebrand disease — the main reason to test; a low or poorly working level causes a bleeding tendency.
- A low factor VIII alongside it — because von Willebrand factor carries factor VIII.
- Easy bruising, nosebleeds, heavy periods, prolonged bleeding after surgery or dental work — the clinical effects.
- A rare acquired form — associated with some other conditions.
When to discuss with a doctor
Von Willebrand factor is tested when a bleeding tendency is suspected — easy bruising, recurrent or prolonged nosebleeds, heavy menstrual periods, bleeding after dental work or surgery, or a family history of a bleeding disorder. Diagnosing von Willebrand disease usually needs the panel together (antigen, activity and factor VIII) and often a repeat, because inflammation, illness, pregnancy and stress raise the level and can mask a mild case. A confirmed deficiency is managed by haematology, with particular attention around surgery, dental procedures, childbirth and, for women, heavy periods; many people manage well with treatment only when needed. Mediora.AI can show von Willebrand factor with factor VIII, platelets and the clotting times so the bleeding-pattern is read together; the diagnosis and management belong with a haematologist.