Clinical QuickieHematology/Coagulation
INR / PT / PTT
These tests measure different parts of coagulation — and none is a universal 'bleeding test.'
PT/INR and PTT answer different questions
PT/INR is commonly used for warfarin effect and extrinsic/common pathway abnormalities; PTT reflects intrinsic/common pathway and selected anticoagulants.
Medication context is essential
Warfarin, heparins, DOACs and liver dysfunction affect coagulation testing differently. Routine PT/PTT may not reliably quantify every anticoagulant.
An isolated abnormality narrows the differential
An isolated prolonged PT/INR, isolated prolonged PTT or both prolonged each point toward different medication/factor/liver/consumption patterns.
Bleeding risk is clinical
Platelets, fibrinogen, liver disease, renal disease, medications, recent procedures and the actual bleeding syndrome matter alongside coagulation tests.
Want more depth?
Read the Deep Dive