Platform
Company
Coagulation
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Currently under review
Pending specialist review and validation.
This test measures the functional activity of Factor X, a key protein in the common pathway of blood clotting. The assay evaluates how well your Factor X is working in your plasma using a standardized 1:20 dilution, which helps minimize interference and improves accuracy.
It is different from anti-Xa drug level tests. Instead of measuring a medication, it assesses your own clotting factor function. Clinicians use it to look for inherited Factor X deficiency, and to detect acquired problems that can reduce Factor X activity, such as liver disease or issues with vitamin K.
Healthy Factor X activity helps your blood clot appropriately after an injury. Doctors may order this test if you have unexplained easy bruising, nosebleeds, heavy menstrual bleeding, prolonged clotting times on screening tests, or a family history of a rare bleeding disorder. It can also be used to evaluate bleeding risk before a procedure or surgery.
Abnormal results can point to different causes. Low activity may reflect an inherited deficiency, vitamin K deficiency, liver disease, or the effect of certain blood thinners. In rare cases, an antibody can interfere with Factor X function. Understanding the reason for an abnormal result guides treatment, which may include addressing nutrition, adjusting medications, or giving specific factor replacement when appropriate.
Your result is interpreted in the context of your symptoms, other lab tests, and medications. Lower-than-expected activity suggests that Factor X is not working properly and may increase bleeding risk. Higher-than-expected activity is uncommon and usually has limited clinical significance, but your care team will consider it alongside the rest of your evaluation.
If your result is outside the expected range, your clinician may review your medication list, check liver function and vitamin K status, or repeat the test. Sometimes additional studies, such as mixing studies or tests for inhibitors, are helpful. Follow-up plans are individualized, and most causes have targeted approaches that can improve clotting and reduce bleeding concerns.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
The blood sample must be collected in a properly filled sodium citrate tube. Underfilling or overfilling can distort clot-based measurements and falsely lower Factor X activity.
Blood drawn from or near a heparinized line can contaminate the sample and depress clot-based factor activity results. A clean peripheral draw and proper discard are important.
Factor X is made in the liver and requires vitamin K. Liver disease or poor vitamin K intake or absorption can reduce activity and lead to abnormal results.
Vitamin K antagonists lower Factor X activity by design. Some direct oral anticoagulants that target factor Xa can interfere with certain assays and appear to reduce activity.
Disseminated intravascular coagulation, severe infections, or major trauma can consume clotting factors and transiently lower Factor X activity until the illness resolves.
Normal physiologic changes in pregnancy and early life can alter coagulation tests. Your clinician will interpret results with these factors in mind.
Rarely, an acquired inhibitor or nonspecific antibody can interfere with Factor X function. Additional testing, such as mixing studies, may be needed to clarify the cause.
Delayed processing, improper storage, or significant hemolysis can affect clot-based assays. Prompt centrifugation and testing improve reliability.
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