Prothrombin Time
Test Mnemonic
PT
CPT Codes
- 85610 - QTY (1)
LOINC ®
34528-0
Aliases
- INR
- PT
Includes
- Prothrombin Time
- INR
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Plasma | Sodium citrate (Lt. Blue) | Centrifuge, aliquot and freeze ASAP. | Collection tube must be filled to total fill volume. Inadequately filled tubes will be rejected. NonTesting Sites: If additional coagulation tests are required on the same tube as the PT/INR, centrifuge, aliquot platelet poor plasma into a separate tube with Epic Beaker label, freeze plasma at -20C, send frozen plasma to Main Campus on dry ice. | |
| 1.8 mL | Whole blood | Sodium citrate (Lt. Blue) | Ambient | Collection tube must be filled to total fill volume. Inadequately filled tubes will be rejected. NonTesting Sites: If samples can arrive at Main Campus within 24 hours, the plasma does not need to be aliquoted and frozen. *If additional coagulation tests are required on the same tube as the PT/INR, centrifuge, aliquot platelet poor plasma into a separate tube with Epic Beaker label, freeze plasma at -20C, send frozen plasma to Main Campus on dry ice. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| N/A | Collection tube must be filled to total fill volume. Inadequately filled tubes will be rejected. |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 24 hours |
| Frozen | 14 days at -20 C; 6 months at -70 C |
| Refrigerated | Unacceptable |
Days Performed
Sun - Sat
Turnaround Time
8 hours
Methodology
| Name | Description |
|---|---|
| Automated Optical Clot Detection |
Special Info
Specimen with hematocrit values > 55 % have spuriously increased prothrombin time values. To correct for this, specimens should be re-collected using a specified whole blood to sodium citrate ratio. Contact the performing lab for specific instructions.
Clinical Info
Evaluation of hemostasis. Recommended Therapeutic Ranges for Oral Anticoagulant use (INR = International Normalized Ratio): INR 2.0 - 3.0: Prevention of venous thrombosis, recurrent DVT, stroke and embolism with tissue heart valves; Treatment of venous thrombosis, PE, TIA, atrial fibrillation and post-myocardial infarction. INR 2.5 - 3.5: Prevention of embolism with mechanical heart valves or lupus anticoagulant. INR 3.0 - 4.5: For reduced recurrence/mortality from stroke and myocardial infarction.