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PROTIME INR (PT)
MessageCoagulation
Test Code
LAB320
Alias/See Also
Prothrombin Time
Protime
PTINR
PT
Protime
PTINR
PT
CPT Codes
85610
Includes
International Normalized Ratio (INR)
Preferred Specimen
Blue top 3.2% citrated tube, plasma
Note: Do NOT place blue top tube on ice
Note: Do NOT place blue top tube on ice
Minimum Volume
2.7 mL whole blood filled to the designated line on specimen container (blue top tube, citrate)
Other Acceptable Specimens
1.8mL Low Volume blue top tube, citrated
Instructions
LAB: Centrifuge in validated Platelet Poor Plasma Centrifuge for 2 minutes at 7200 rpm. Specimen to be delivered to Coagulation department STAT. Notify CLS upon arrival.
**Testing must be completed within 24 hours of collection.
Note: If unable to deliver whole blood to testing laboratory within stability time, platelet poor plasma should be aliquoted and placed in freezer. Centrifuge light blue-top for 2 minutes at 7200 rpm (STAT Coag centrifuge) within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge aliquoted plasma a second time and transfer platelet-poor plasma into a new plastic vial and freeze at -20℃. Once thawed, specimen must be tested within 2 hours.
Freeze aliquot at -20℃ for at least 1 hour when sending to alternate campus for testing.
**Testing must be completed within 24 hours of collection.
Note: If unable to deliver whole blood to testing laboratory within stability time, platelet poor plasma should be aliquoted and placed in freezer. Centrifuge light blue-top for 2 minutes at 7200 rpm (STAT Coag centrifuge) within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge aliquoted plasma a second time and transfer platelet-poor plasma into a new plastic vial and freeze at -20℃. Once thawed, specimen must be tested within 2 hours.
Freeze aliquot at -20℃ for at least 1 hour when sending to alternate campus for testing.
Transport Container
Ambient: blue top tube, whole blood (24 hours)
Frozen: processed platelet poor plasma
Frozen: processed platelet poor plasma
Transport Temperature
Ambient: whole blood (stable 24 hours)
Frozen (-20℃): plasma frozen for at least 1-2 hours
Frozen (-20℃): plasma frozen for at least 1-2 hours
Specimen Stability
Whole Blood: Ambient 24 hours
Plasma separated from whole blood Room Temp: 24 hours
Plasma separated from whole blood 2-8°C: Unacceptable
Plasma separated from whole blood -20°C: 2 weeks
Plasma separated from whole blood -70°C: 6 months
Plasma separated from whole blood Room Temp: 24 hours
Plasma separated from whole blood 2-8°C: Unacceptable
Plasma separated from whole blood -20°C: 2 weeks
Plasma separated from whole blood -70°C: 6 months
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolyzed, clotted specimen, contaminated, underfilled tube – QNS, overfilled tube, whole blood specimen transported on ice
Methodology
Thromboplastin and calcium ions combined patient plasma initiates the activation of the extrinsic pathway. This results in the conversion of fibrinogen to fibrin, with the formation of a solid gel. The time required for clot formation is measured in seconds.
Report Available
STAT: 1 hour
Routine: Same Day
Routine: Same Day
Limitations
Patients with in-dwelling catheters should have coagulation studies drawn from the catheter unless specified "peripheral" by the physician. Procedures for in-dwelling catheter draw: 1. If ONLY a coagulation test is required, the first 20 ml of blood drawn must be discarded before the specimen for coagulation testing can be obtained. 2. If specimens for other laboratory tests IN ADDITION to a specimen for coagulation testing are required, the first 8 to 10 ml. of blood drawn must be discarded. A second syringe of blood can then be obtained for all tests other than the coagulation test (e.g. Chemistry, Hematology, Blood Bank, or Microbiology). Following that , a third syringe should then be used to draw the coagulation sample.
Reference Range
Protime: 9.4 - 12.5 seconds
INR: 0.8 - 1.1 seconds
Critical Value: INR >6.0
INR: 0.8 - 1.1 seconds
Critical Value: INR >6.0
Clinical Significance
The Prothrombin Time test (PT) is a global screening test with three major applications. These include:
Detection of single or combined deficiencies of the extrinsic coagulation pathway indicative of hereditary and acquired coagulation disorders, liver disease or vitamin K deficiency.
Monitoring test for oral anticoagulant therapy
Assay for specific extrinsic coagulation factors
Detection of single or combined deficiencies of the extrinsic coagulation pathway indicative of hereditary and acquired coagulation disorders, liver disease or vitamin K deficiency.
Monitoring test for oral anticoagulant therapy
Assay for specific extrinsic coagulation factors
Performing Laboratory
HHN/HHI
