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PROTIME INR (PT)
MessageCoagulation
Test Code
LAB320
Alias/See Also
Prothrombin Time
Protime
PT
Protime
PT
CPT Codes
85610
Includes
International Normalized Ratio (INR)
Preferred Specimen
2.7 ml. whole blood (blue top tube, citrate) TUBE MUST BE FULL
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
PT: testing must be completed within 24 hours of collection.
LAB: Centrifuge in validated Platelet Poor Plasma Centrifuges only
Transport Container
Processed Platelet Poor Plasma, preferably frozen
Transport Temperature
Processed Platelet Poor Plasma:
Room Temp – 24 hours
Refrigerated – Unacceptable
Frozen – 2 weeks
Room Temp – 24 hours
Refrigerated – Unacceptable
Frozen – 2 weeks
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?)
Underfilled tube - Quantity not Sufficient (QNS)
Clotted specimen
Clotted specimen
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
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
