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Test Code 02F Prothrombin Time with INR

Important Note

Anticoagulation Fact Sheet for Clinical Monitoring

Additional Codes

ALAB: PTINR

PowerChart: Protime with INR

MA Cerner: PT

Test Method

Protime: Detection of Clot Formation; ACL Systems

INR: calculations

Specimen Requirement

BD sodium citrate blue-top tube filled to or above the etched line on the tube.

 

Greiner VACUETTE sodium citrate blue-top tube filled to the area within the indicator arrow printed on the side of the tube.

Additional Specimen Collection Information

Invert the sodium citrate tube end to end 4 times to thoroughly mix blood and anticoagulant. The tube should be left stoppered until time of testing. 1+ hemolysis is unacceptable. Specimens stored at room temperature should be centrifuged and tested within 24 hours of specimen collection. If the testing is not completed within 24 hours the plasma should be removed from the cells and transferred to a plastic tube. Freeze the sample for up to two weeks. Frozen samples should be rapidly thawed at 37°C while gently mixed. Thawed samples should be centrifuged and tested immediately. If testing of thawed samples cannot be performed immediately the sample may be held for a maximum of 2 hours refrigerated, until tested.

  • Precautions:

    • It is not recommended to use a winged blood collection set (Butterfly).
    • If a vacuum tube butterfly must be used, the first tube in the series will be under-filled. Collect a “discard citrate tube”, and then collect the citrate tube used for testing. This will ensure the proper blood to anticoagulant ratio.
    • If using a syringe, use a BD Blood Transfer Device to transfer blood from the syringe to the citrate tube within one minute of collection. Hold the syringe with the plunger in the up-right position and allow the vacuum present to fill the tube. Before collection, be sure the syringe plunger is pushed to the top of the syringe. The transfer device may pop up and needs to be held down to completely fill tube to between fill lines.
    • Do not “force fill” blood into a vacuum tube. This may result in activation of the platelets possibly leading to erroneous results. Allow the vacuum present to fill the tube.
    • Do not remove vacuum tube cap to add blood.
    • Specimens should be obtained from a single venipuncture with minimal tissue trauma. Never combine multiple blood collections into a single vacuum tube.
    • Never re-use a syringe that was used for a pic line saline flush.

Refer to the "Citrated Plasma for Coagulation Studies" protocol in the Quality Assurance Manual.

Performance

Testing is performed Monday through Sunday.

Routine orders: Typically completed within 4 hours after the specimen arrives at the testing site.

Expedite orders: Typically completed within 1 hour after the specimen arrives at the testing site.

STAT orders: Typically completed within 25 minutes after the specimen arrives at the testing site.

Reference Values

Prothrombin Time: 9.4-12.5 Seconds

INR: 0.8-1.2

INR Therapeutic Range is dependent upon the clinical circumstances:

  • Standard intensity warfarin therapeutic range: 2.0 to 3.0.
  • High intensity warfarin therapeutic range: 2.5 to 3.5.
     
  • Critical value: > 5.0 (for oral anticoagulated patients)
    This correlates to a prothrombin time of about 46.5 seconds, dependent on the system used.

CPT Code Information

85610 Coagulopathy Testing: Prothrombin Time

Useful For

Monitoring intensity of oral anticoagulant therapy when combined with INR reporting

Screening assay to detect deficiencies of 1 or more coagulation factors (factors I, II, V, VII, X) due to:

Hereditary or acquired deficiency states

Vitamin K deficiency

Liver disease

Specific coagulation factor inhibitors

Screening assay to detect coagulation inhibition ("circulating anticoagulants") associated with:

Specific coagulation factor inhibitors

Lupus-like anticoagulant inhibitors (antiphospholipid antibodies)

Nonspecific prothrombin time inhibitors (eg, monoclonal immunoglobulins, elevated fibrin degradation products)

LOINC Code Information

5902-2 Prothrombin Time (PT) In Platelet Poor Plasma By Coagulation Assay

6301-6 INR In Platelet Poor Plasma By Coagulation Assay