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Prothrombin Time

PT Thromboplastin Time
Sodium citrate (blue top) seconds

About this test

Time for plasma to clot after addition of thromboplastin (tissue factor + Ca²⁺). Evaluates the extrinsic (factor VII) and common coagulation pathways. Expressed as INR for anticoagulation monitoring.

Reference Ranges

Sex Age Range Notes
All ≥ 18 yrs 11 – 13.5 Adult; varies by lab (thromboplastin reagent). INR = PT ratio^ISI

Clinical Interpretation

Low / Decreased
Short PT — hypercoagulable state (rarely tested).
High / Increased
Prolonged — warfarin, liver disease, vitamin K deficiency, DIC, factor VII, X, V, II, or fibrinogen deficiency, direct thrombin/Xa inhibitors (variably).

Related Tests

INR Fibrinogen
Specimen
Sodium citrate (blue top)
Reporting Unit
seconds
Category
🩹 Coagulation

⚠ Clinical Note
Reference ranges are indicative. Always interpret results in the context of the individual patient and local laboratory reference intervals, which may vary.