Platform
Company
Coagulation
Review status
Currently under review
Pending specialist review and validation.
This test measures the activity of Factor II, also called prothrombin, a protein made by your liver that helps your blood clot. It looks at how well Factor II is working in your plasma using a clot-based method.
The term 1:5 refers to a fixed dilution used during the assay. Using a set dilution helps place the sample in the assay’s optimal measuring range and can aid the lab in detecting assay interference. The result reflects the functional performance of Factor II, not just the amount present.
Your care team may order this test if you have unexplained bleeding, bruising, an abnormal screening clotting test, or a known or suspected clotting factor problem. It can help distinguish between a true deficiency of Factor II and situations where other conditions are interfering with clotting.
Abnormal Factor II activity can be seen with liver disease, low vitamin K, use of certain blood thinners, or a rare inherited deficiency. Results can guide next steps, such as evaluating vitamin K status, reviewing medications, checking for inhibitors, or considering targeted treatment when appropriate.
A lower-than-expected Factor II activity suggests reduced function of this clotting protein. This can happen with vitamin K–related issues, liver dysfunction, or the effect of certain medicines. Your clinician may confirm the finding with repeat testing, mixing studies, or additional coagulation tests to pinpoint the cause.
A result within the expected range usually means Factor II function is adequate. If you still have symptoms, your clinician may look at other clotting factors or related conditions.
A higher-than-expected activity can occur in some settings and does not always signal a problem. Interpretation always depends on your history, medications, and other lab results. If results are unexpected, your clinician may review sample quality, timing of collection, and potential medication effects before deciding on further testing.
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.
Incorrect blood-to-citrate ratio, underfilled tubes, high hematocrit, hemolysis, or delayed processing can alter clot-based results and lead to misleading findings.
Vitamin K antagonists, direct thrombin or factor Xa inhibitors, and in some cases heparin can lower measured activity or interfere with clot assays. Always list all medicines and supplements.
Factor II is made in the liver and requires vitamin K. Liver disease or poor vitamin K intake or absorption can reduce Factor II activity.
Specific inhibitors to factor proteins or nonspecific inhibitors such as lupus anticoagulant can affect clot-based assays, sometimes mimicking a deficiency.
Recent doses of anticoagulants, recent transfusion, or acute illness can transiently change results. Your clinician may adjust timing or repeat testing for clarity.
Pregnancy, newborn period, and advanced age can influence coagulation assays. Interpretation may require population-specific context.
References