Decreased prothrombin time 2019-01-19T15:32:55Z Decreased international normalised ratio Decreased international normalized ratio Decreased INR Decreased PT Abnormally short time to coagulation in the prothrombin time test, which is a measure of the extrinsic pathway of coagulation. The results of the prothrombin time test are often expressed in terms of the International normalized ratio (INR), which is calculated as a ratio of the patient's prothrombin time (PT) to a control PT standardized for the potency of the thromboplastin reagent developed by the World Health Organization (WHO) using the formula: INR is equal to Patient PT divided by Control PT. Abnormal prothrombin time