INR
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Assay |
International Normalised Ratio (INR) |
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Key Words |
PT, INR, International Normalised Ratio |
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Specimen Collection |
3.0ml Citrate (Green lid). 1.4ml Citrate for paediatric (Green lid). Fill to mark. Samples older than 24 hours on receipt cannot be processed. |
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Turnaround time |
Less than 8 hours. |
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Test indications |
Warfarin dose monitoring |
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Interferences |
Lipaemia, haemolysis, anticoagulants, antiphospholipid syndrome. The antibiotic oritavancin has been shown to react with certain coagulation reagents; it may artificially prolong the PT INR for approximately 12 hours post-dosage. |
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Reference Range |
See table below |
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Minimum retesting interval |
N/A |
| Target INR (BJH 1998 101: 374-387) | Target | Range |
| Atrial fibrillation | 2.5 R | 2.0 - 3.0 R |
| All single venous thromboembolic events | 2.5 R | 2.0 - 3.0 R |
| Recurrence of venous thromboembolism (Not on Warfarin Rx) | 2.5 R | 2.0 - 3.0 R |
| Recurrence of venous thromboembolism (On Warfarin Rx) | 3.5 R | 3.0 - 4.0 R |
| Anti Phospholipid Syndrome | 3.5 R | 3.0 - 4.0 R |
| Mechanical prosthetic heart valves | 3.5 R | 3.0 - 4.0 R |
