Coagulation studies

Question 1

Prothrombin time (PT)

Answer 1

11–15 seconds

Time it takes to produce fibrin polymers after adding thromboplastin and calcium

Question 2

International normalized ratio (INR)

Answer 2

0.9–1.1

Derived from PT, but calculated by comparing the laboratory-specific PT to a standardized PT

Question 3

(Activated) partial thromboplastin time (aPTT, PTT)

Answer 3

25–40 seconds

Time it takes to produce fibrin polymers after adding phospholipids

Question 4

(Plasma) thrombin time (TT)

Answer 4

< 2 seconds deviation from control

Time it takes to produce fibrin polymers after adding thrombin