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Protime
MessagePerforming Lab: Hudson, Lakeview, Regions, Westfields
Test Code
0021a
Alias/See Also
Sunquest: APRO; Prothrombin Time, PT, Protime, INR
CPT Codes
85610
Includes
Protime; INR
Preferred Specimen
2.7 mL (in 3 mL tube) 3.2% sodium citrate (light blue-top) tube filled to fill line on the tube.
Minimum Volume
1.0 mL
Instructions
Collection:
Samples with a hematocrit > 55% require a special anticoagulant adjusted tube for high hematocrits.
Processing:
Freeze an aliquot of plasma at -20°C if not performed within 24 hours of collection
Samples with a hematocrit > 55% require a special anticoagulant adjusted tube for high hematocrits.
Processing:
Freeze an aliquot of plasma at -20°C if not performed within 24 hours of collection
Transport Temperature
Room Temperature
Specimen Stability
Regions:
Room Temp = 24 Hours
Refrigerated = 24 Hours
Frozen -20C = 72 Hours
Frozen -80C = 2 Weeks
Westfields: Centrifuged 8 hours
Room Temp = 24 Hours
Refrigerated = 24 Hours
Frozen -20C = 72 Hours
Frozen -80C = 2 Weeks
Westfields: Centrifuged 8 hours
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolyzed or Clotted Samples, Samples do not meet the minimum draw requirements, Samples exceed maximum draw requirements, Samples with hematocrit >55% not collected with the special tube.
Methodology
Electromagnetic Clot Detection
Setup Schedule
Daily
Report Available
Same day.
Limitations
The INR (International Normalized Ratio) is useful in monitoring patients on stable Coumadin therapy and allows for comparison of results between laboratories using different reagents and analyzers. The effects of Coumadin become unapparent after meds have been discontinued for 7 days.
If the patient’s hematocrit is greater than 55%, special tubes with less anticoagulant must be used for specimen collection.
Thrombin inhibitors present in the sample may lead to prolonged prothrombin times.
If the patient’s hematocrit is greater than 55%, special tubes with less anticoagulant must be used for specimen collection.
Thrombin inhibitors present in the sample may lead to prolonged prothrombin times.
Reference Range
Protime: 12.0 - 14.5 seconds (Lakeview Only: 9.3 - 11.5 seconds)
INR: 0.9 - 1.1
Critical: INR: >= 5.0
INR: 0.9 - 1.1
Critical: INR: >= 5.0
Clinical Significance
The PT is commonly used for monitoring oral anticoagulant (warfarin) therapy because of its sensitivity to variations in the concentration of Vitamin-K dependant factors II, VII and X. Useful in the assessment of congenital and/or acquired deficiencies of the extrinsic coagulation pathway (factors II, V, VII, and X). A prolonged PT has been observed in the following clinical states: treatment with Vitamin K antagonists, hemorrhagic disease of the newborn, intestinal reabsorption disorders, liver failure (cirrhosis, hepatitis, jaundice) and fibrinolysis.
