Why the test is performed
To assess part of the clotting pathway and standardise monitoring of vitamin-K antagonist anticoagulation.
World time
Laboratory Testing Online / Hematology
Prothrombin Time and INR (PT/INR)
To assess part of the clotting pathway and standardise monitoring of vitamin-K antagonist anticoagulation.Test profileHEProthrombin Time and INR (PT/INR)
Test and specimen
What is being examined?
- Test
- Prothrombin Time and INR (PT/INR)
- Department
- Hematology
- Typical sample or measurement
- Correctly filled citrate plasma
Before the test
Follow medication and timing instructions. Never stop anticoagulants unless the prescriber directs it.
Clinical interpretation
Laboratory results should be interpreted by a qualified professional using the correct reference interval, method, symptoms, history and other findings. A normal or abnormal value rarely confirms or excludes a condition by itself.
What the test is used for
Investigating abnormal bleeding, assessing liver-related clotting changes, pre-procedure review and monitoring warfarin where prescribed.
How the test is performed
Calcium and a tissue-factor reagent are added to platelet-poor plasma; clotting time is measured and may be converted to an INR.
Conditions and diseases considered
May be abnormal in vitamin K deficiency, liver disease, clotting-factor deficiencies, anticoagulant effect or disseminated coagulation disorders.
Recommended further tests
aPTT, fibrinogen, platelet count, mixing study, liver profile or specific factor assays depending on context.
Primary public reference
Continue with the official patient guide.
COHSEW has summarised this information for navigation and awareness. Follow the source and your healthcare provider’s current instructions for the complete context.
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