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Test Code LAB320 Protime/INR

Important Note

Blue tubes that are not filled to the required line will not be processed, due to result integrity being affected.  

Useful For

  • Measuring the activity of the extrinsic coagulation pathway (factors I, II, V, VII, and X)
  • Monitoring Coumadin therapy

Methodology

Clot Detection

Performing Laboratory

Bozeman Health Laboratory Services

Specimen Requirements

 

Specimen Type: Whole blood
Container/Tube: Blue top (3.2% sodium citrate)

Specimen Volume: Full tube

Collection Instructions:   Click here to link to a You Tube video tutorial

1. Immediately after draw, invert tubes several times to mix blood with additive.

2. Send specimen in original tube.

3. If there is a delay in transport of >24 hours, specimen must be double-centrifuged to prepare a platelet-free plasma specimen as follows:

a. Immediately centrifuge at 3,200 rpm for 15 minutes.

b. Carefully remove plasma from cells avoiding platelet/buffy coat, and transfer plasma into a plastic tube.

c. Centrifuge plastic tube at 3,200 rpm for 15 minutes.

d. Carefully remove top portion of plasma and transfer plasma into a plastic tube leaving approximately 250 mL in bottom to discard.

e. Double-centrifuged plasma should be aliquoted (0.5 mL-1 mL each) into clearly labeled plastic tubes. (Glass vial is not acceptable.)

Note: Number of tests ordered will determine number of aliquots needed, generally 1 aliquot per test.

f. Specimens should be frozen at <-40° C, if possible, and sent together in same container with at least 5 lbs of dry ice. Specimens must arrive in a frozen state.

Additional Information: Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

Specimen Transport Temperature

Ambient (whole blood) <24 hours/Frozen (plasma) >24 hours

Specimen Stability

Specmen Type Temperature Time
Whole Blood (unspun) Ambient 24 hours
Plasma Na Citrate (spun) Ambient 8 hours
Plasma Na Citrate (double spun) Frozen 14 days

Reference Values

PT: 12.0-14.5 seconds

INR: 0.90-1.1

 

Critical value (automatic call-back): >5.00

 

INR Standard Intensity: 2.0-3.0

INR Higher Intensity: 2.5-3.5

 

Note: Reference values change with each new reagent lot. Check with laboratory or refer to reference range on computer reports.

Additional Information

  • Testing includes prothrombin time and International Normalized Ratio (INR)
  • A prolonged PT has been observed in the following clinical states:

    • congenital or acquired deficiencies of factor II, V, VII, X or fibrinogen
    • liver failure (cirrhosis, hepatitis)
    • treatments with vitamin K antagonists
    • hypovitaminosis K: nutritional intake deficiency, disorders in absorption    or metabolism of vitamin K (hemorrhagic disease of the newborn, cholestasis, treatment with antibiotics)
    • fibrinolysis
    • DIC

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

85610