Prothrombin Time with INR (PT/INR)

CPT Code(s):

  • 85610

Preferred Specimen:

Whole Blood. (One full unopened 3.2% sodium citrate (light blue-top) tube)

Minimum Volume:

Ratio of blood to citrate is critical. Submit difficult draws in pediatric tube. 0.5 mL frozen plasma

Alternate Specimen:

1 mL frozen plasma: If the specimen will be delayed longer than 12 hours, centrifuge specimen for 15 minutes at 2500-3500 rpm. Using a plastic pipette, remove plasma, taking care to avoid the WBC/ platelet (buffy) layer and place into a plastic screw-cap vial and freeze at -20¡C.

Special 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 (unless plasma is to be frozen)

Transport Container:

Whole blood: 3.2% sodium citrate (light blue-top) tube Plasma: Plastic screw-cap vial (frozen)

Transport Temperature Name:

Room temperature: Light blue-top tube (whole blood) Frozen: Plasma

Specimen Stability Components:

  • Room Temperature: Unopened light blue-top tube Room temperature: 24 hours Separated platelet-poor plasma Frozen -20¡C: 7 days

Testing Schedule:



Mechanical Clot Detection

Reference Range:

PT: 11.6 Ð 15.8 seconds (Reagent lot specific) INR: 0.79 Ð 1.21

Reject Criteria:

Gross hemolysis, Gross lipemia, improper blood to citrate ratio, High hematocrit, improper blood collection

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