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Test Code PTIM Prothrombin Time with INR LAB320

Test Method

Protime: Detection of Clot Formation; ACL Systems

INR: calculations


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.

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

Vitamin K deficiency

Liver disease

Specific coagulation factor

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

Specific coagulation factor

Lupus-like anticoagulant inhibitors
(antiphospholipid antibodies)

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

Specimen Requirement

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

CPT Code Information

85610 Coagulopathy Testing: Prothrombin

Reference Values

Prothrombin Time: 9.4-12.5 Seconds

INR: 0.8-1.2

INR Therapeutic Range is dependent upon the clinical

  • Standard intensity warfarin therapeutic range: 2.0 to
  • 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.

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

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
    • 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

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