Description
Factor XI activity is a measure of the level of factor XI in the blood, which is a coagulation protein that helps blood clot. The normal range for factor XI activity is 65–130 U/dL, or 65–130%. A lower than normal level may indicate factor XI deficiency, a rare condition that's more common in people of Ashkenazi Jewish descent.
A factor XI activity assay measures the time it takes for a sample of plasma to clot after calcium is added. The assay compares the clotting time of the patient's plasma to that of normal plasma.
Factor XI deficiency can cause a number of bleeding problems, including:
- Prolonged bleeding after surgery or trauma, particularly in the mouth, nose, or urinary tract
- Frequent nosebleeds
- Easy bruising
- Bleeding under the skin
- Bleeding gums
- Heavy or prolonged menstrual bleeding in women
However, most people with factor XI deficiency have relatively mild bleeding problems, and some have few or no symptoms.
Fasting not required.
