Plasma Prothrombin Ratio
Synonyms
Prothrombin time (PT)
Purpose
Plasma Prothrombin Ratio test is used to screen for and diagnose bleeding and clotting disorders. The international normalized ratio (INR) is calculated from the prothrombin time and used to monitor anticoagulation therapy.
Patient Preparation
There are no special preparations for this test. The patient, however, should inform the physician about medications they are taking.
Samples
2.7 ml of whole blood plasma collected in Sodium citrate tube (blue top). Sample should be gently mixed after collection for adequate mixing of the anticoagulant with blood. The sample collection tube should not be opened unless plasma will be frozen for storage. In case of intended delays in testing, the sample should be centrifuged for 10min and plasma separated and frozen immediately at 40c, until testing.
Reference Range
Usually reported as INR.
INR: 2 – 3.5
Results Turnaround
Within 24 hours after sample collection.
Diseases / Diagnostic indicators
Abnormal PT/INR results usually indicate a clotting disorder, a bleeding disorder, vitamin K deficiency or a liver disease. Results are also affected by anticoagulation therapies.