Specimen

3 mL Whole blood in 1 Blue Top (Sodium Citrate) tube. Mix thoroughly by inversion. Transport to Lab within 4 hours. If this is not possible, make PPP within 1 hour of collection as follows: Centrifuge sample at 3600 rpm for 15 min. & transfer supernatant to a clean plastic tube. Centrifuge this supernatant again at 3600 rpm for 15 min. & finally transfer the supernatant (PPP) to 1 labelled clean plastic screw capped vial. FREEZE IMMEDIATELY. Ship frozen. DO NOT THAW. Overnight fasting is preferred. Duly filled Coagulation Requisition Form (Form 15) is mandatory. It is recommended that patient discontinues Heparin for 1 day and Oral Anticoagulants for 7 days prior to sampling as these drugs may affect test results. Discontinuation should be with prior consent from the treating Physician.

Usage

Prothrombin time measures the time it takes for plasma to clot when exposed to tissue factor. Since PT comprises reactions of coagulation that occurs in tissue injury & common pathways of coagulation, deficiencies in the activity of Factors II, V, VII, X or fibrinogen may prolong the PT. INR standardizes the reporting of PT values in Warfarin anticoagulated patients.