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Prothrombin Time with INR
Test Code8847
CPT Codes
85610
Preferred Specimen
1 mL frozen plasma collected in a 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Instructions
A completely filled tube is necessary because the correct ratio of blood to citrate is critical (9:1). Mix by gentle inversion 3-4 times. Do not uncap.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 14 days
Refrigerated: Unacceptable
Frozen: 14 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Improper blood to citrate ratio • High hematocrit • Improper blood collection
Methodology
Photo-Optical Clot Detection
Setup Schedule
P.M. Sets up 5 days a week.
Limitations
Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): little to no effect (reagent contains a heparin neutralizer); Dabigatran or Argatroban (Thrombin Inhibitors): normal to prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.
Clinical Significance
Screening test for abnormalities of coagulation factors that are involved in the extrinsic pathway. Also used to monitor effects of Warfarin therapy and to study patients with hereditary and acquired clotting disorders.
