PT ratio

Overview

The PT ratio (prothrombin time ratio) is a measure of blood clotting that compares a patient’s prothrombin time to a laboratory control. It reflects function of the extrinsic and common coagulation pathways (factors I, II, V, VII and X) and is used to assess bleeding risk and monitor anticoagulation. Abnormal PT ratio may indicate liver disease, vitamin K deficiency, warfarin excess, disseminated intravascular coagulation (DIC), or inherited clotting factor deficiencies. Symptoms prompting testing include unexplained or excessive bleeding, easy bruising, prolonged bleeding after procedures, hematuria or GI bleeding. Newborns normally have longer PTs; anticoagulant therapy, acute illness and pregnancy can alter results.

Test Preparation

• Fasting not required, avoid certain medications if advised

Why Do I Need This Test

• Which profile is the test included in: usually part of a coagulation/hemostasis panel (often ordered together with CBC and INR).
• Symptoms indicating the test: unexplained bleeding/bruising, prolonged post‑procedural bleeding, suspected DIC or liver dysfunction.
• Conditions it diagnoses/monitors: liver disease, vitamin K deficiency, monitoring warfarin therapy, DIC, clotting factor deficiencies.
• Reasons for abnormal levels: anticoagulants, liver failure, vitamin K deficiency, DIC, malabsorption, lab/reagent variability.
• Biological meaning: prolonged PT ratio = slower clot formation; shortened ratio = faster clotting or assay variation.
• Behaviors/lifestyle: alcohol abuse, poor diet (vitamin K), herbal supplements, medication (warfarin/antibiotics).
• Family history: inherited coagulation disorders or bleeding tendency.

Understanding Test Results

• A PT ratio within 0.8–1.2 is considered normal.
• Values >1.2 indicate mild prolongation and may reflect early liver dysfunction, mild vitamin K deficiency, or low‑dose anticoagulation.
• Ratios 1.3–1.5 are clinically significant and suggest moderate coagulopathy or therapeutic anticoagulation requiring review.
• Ratios ≥1.5–2.0 carry increased bleeding risk; values >2.0 indicate severe coagulopathy seen in acute liver failure, DIC, or warfarin overdose and prompt urgent evaluation.
• A low ratio (<0.8) is uncommon; it may reflect hypercoagulable state, assay variability, or acute phase effects (eg, pregnancy, high fibrinogen) and usually requires correlation with clinical context and further testing (INR, mixing studies, factor assays, LFTs).

FAQs