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ProThrombin Time/INR
Test CodePT
Alias/See Also
INR, PT, PTINR, Protime, Prothrombin Time
CPT Codes
85610
Preferred Specimen
Citrate BLUE (BLU)
Minimum Volume
Citrate vacutainer tube must be filled to the "fill line."
Other Acceptable Specimens
NONE
Instructions
Collect whole blood in 3.2% buffered sodium citrate (9:1 blood to sodium citrate). Venipuncture must be atraumatic.
Specimen Stability
- Refrigerated/Ambient Temperature: Specimens for PT assays uncentrifuged or centrifuged, when kept at 2 to 4°C or 18 to 24°C, should be tested within 24 hours from the time of specimen collection.
- Frozen Plasma: If testing is to be delayed more than 24 hours after collection, immediately separate plasma into a clean, polystyrene tube, cap, and store below –20°C up to two weeks or -70°C up to 6 months.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Reject hemolyzed, clotted, overfilled tubes or short draw (<90%) samples
Setup Schedule
24x7
Report Available
24x7
Limitations
AMR: Protime: 10-200 Seconds
INR: 0.8-20 INR
INR: 0.8-20 INR
Reference Range
Protime Normal: 12.0-14.7 seconds
INR: 0.8-1.1 Ratio
Critical INR: > 5.0 Ratio
INR: 0.8-1.1 Ratio
Critical INR: > 5.0 Ratio
| Recommended INR Ranges for Monitoring Stable Oral Anticoagulant Therapy | INR Range | INR Target |
| All Conditions except Mechanical Heart valves | 2.0-3.0 | 2.5 |
| Mechanical Heart Valves | 2.5-3.5 | 3.0 |
Clinical Significance
The prothrombin time (PT) can help diagnose bleeding or clotting disorders.
The INR is used to monitor the blood-thinner warfarin/counadin treatment.
The INR is used to monitor the blood-thinner warfarin/counadin treatment.
Performing Laboratory
CRMC Laboratory
CCMC Laboratory
FHSH Laboratory
