Test Code PT Prothrombin Time (PT) and International Normalized Ratio (INR), Plasma
Methodology
TurbidometricPerforming Laboratory
Aspen Valley HospitalPhysician Office Specimen Requirements
Container/Tube: Light blue-top (sodium citrate) tube(s)Specimen: 1 mL of sodium citrate plasma
Transport Temperature: Ambient
Collection Instructions: If there is a delay in transport of >4 hours, spin down and send 1 mL of platelet-poor plasma frozen in plastic vial.
Reference Values
PROTIMEPatients not taking anticoagulants: 11.2-15.5 seconds
INR
Therapeutic ranges for oral anticoagulation therapy:
In the typical case of venous thrombosis, the target INR is 2.0-3.0. The optimal target range is not the same for all indications. Universal agreement has not been reached on the optimal range for the various indications. For in-depth recommendations and an extensive review see “Chest,” 2008; 133: no. 6 suppl: 71S-109S.
Critical value (automatic call-back): ≥5.0 (INR)