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Test Code PTIM Prothrombin Time with INR (PT) [LAB320]

Test Method

Protime: Mechanical Clot Detection, Diagnostica Stago

INR: Calculated

Performance

Testing is performed Monday through Sunday.

Routine orders: Typically completed within 4 hours upon receipt in the lab.

STAT orders: Typically completed within 25 minutes upon receipt in the lab.

Specimen Requirement

  1. Sodium citrate blue-top tube filled to the area within the indicator arrow printed on the side of the tube.
    Important: Underfilled and overfilled tubes will be rejected.
  2. Transport tube to the lab as soon as possible. Tubes should be spun within one hour of collection and tested within 24 hours of collection.
  3. Never refrigerate specimens for protime testing.
  4. If the specimen cannot be sent to the lab immediately, spin down and remove plasma from the cells and freeze to at least -20C. The specimen must then remain frozen during transport to the lab.
  5. Blood collection using a butterfly needle is not recommended. If using a winged butterfly setup, collect a "discard tube" first to account for the dead space in the butterfly tubing. 
  6. Do not "force fill" into a vacutainer tube.
  7. Do not remove the cap of a blue top citrate tube.

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)

Reference Values

Prothrombin Time: 12.1 - 15.0 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