Test Code LAB320 Protime/INR
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