Platform
Company
Coagulation
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Currently under review
Pending specialist review and validation.
Factor II, also called prothrombin, is a protein made by the liver that helps your blood form stable clots. This test measures how well factor II works in your plasma using a functional assay that is reported in activity units. The one-to-ten dilution in the method helps keep the measurement in a reliable range and limits interference, so the result reflects true factor function.
It is typically performed alongside clotting time tests and, when needed, other individual factor assays or mixing studies. The test helps clarify whether a clotting problem is due to a specific factor deficiency, an inhibitor, or another cause.
Your clinician may order this test if you have unexplained bleeding, easy bruising, prolonged clotting times, or a suspected inherited factor II deficiency. It can also help evaluate the impact of liver disease, nutrition affecting vitamin K, or the effects of anticoagulant medicines that reduce factor II activity.
Understanding factor II activity helps separate low production from the presence of an inhibitor and guides next steps. Results can inform treatment such as vitamin K supplementation, adjusting anticoagulant therapy, or referring to a hematology specialist for further evaluation.
A result that is lower than expected suggests reduced factor II activity. This can be due to inherited deficiency, impaired production from liver disease or low vitamin K, effects of certain medicines, or the presence of an antibody that interferes with clotting. Higher than expected activity is uncommon and often of limited clinical significance, but repeat testing and correlation with other results may be advised.
Your provider will interpret this result together with your symptoms, clotting times, and other factor assays. If an inhibitor is suspected, additional tests such as a mixing study may be ordered. When there is concern about collection or handling issues, a fresh sample collected in the correct tube and processed promptly may be requested to confirm the result.
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.
Underfilling or overfilling the blue-top citrate tube, delays in processing, extreme temperatures, or clotted or hemolyzed specimens can falsely lower or raise measured activity. Proper venipuncture, correct tube fill, and prompt centrifugation are important.
Vitamin K antagonists, direct thrombin inhibitors, direct factor Xa inhibitors, and heparin can reduce activity or interfere with the assay. Your care team needs a complete list of your medicines and timing of your last doses.
Factor II is made in the liver and requires vitamin K. Liver disease or poor vitamin K intake or absorption can reduce factor II production and lower activity results.
Specific antibodies against factor II or nonspecific inhibitors such as lupus anticoagulant can affect clot-based assays. Additional tests, including mixing studies, may be needed to sort out these effects.
Recent plasma transfusion or administration of prothrombin complex concentrate can temporarily raise measured activity and may mask an underlying deficiency.
Physiologic changes during pregnancy and acute inflammatory states can shift some coagulation measurements. Your provider will interpret results in clinical context.
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