International Normalised Ratio (INR)

Background

This section is intended for those on blood-thinning medications like warfarin, with an existing diagnosis of atrial fibrillation or a mechanical heart valve. If you are experiencing symptoms of chest pressure, shortness of breath, palpitations, suspecting an underlying cardiac diagnosis or are bleeding, please go to your nearest emergency room.

Why does TeleTest offer INR testing?

Many Canadians on warfarin do not have access to routine primary care monitoring, resulting in sub-optimal monitoring of their INR. INR levels outside of clinically indicated ranges increase one’s risk of stroke and/or heart attack. We hope to facilitate accurate and timely monitoring of your INR. If you have an INR outside of your normal range, a physician from TeleTest will call you, review your clinical indication and recommend adjustment of your warfarin and a repeat test interval to ensure your INR returns to a normal range.

Do I need to get tested if I am on a NOAC?

If you are on a Non-Vitamin K Oral Anticoagulant (NOAC), you do not require serial monitoring of your INR levels. Examples of NOACs include apixaban (eliquis), rivaroxaban (xarelto), dabigatran (pradaxa), edoxaban (lixiana). Warfarin is the only anti-coagulant used that requires monthly monitoring of your INR, and sometimes with dose changes more frequent monitoring is required. When your INR is in the right range for your medical condition, it is considered ‘therapeutic’.

When is warfarin used?

Warfarin is an anticoagulant used in the following medical conditions [1] :

• Mechanical heart valve

• Valvular atrial fibrillation (mitral stenosis, biprostetic mitral valve)

• Severe kidney disease (sometimes)

• Severe liver disease (sometimes)

• History of pulmonary embolus (blood clot in your lung)

• History of deep venous thrombosis (blood clot in a large vein)

What are the target ranges for my INR?

INR monitoring is NOT used when you are on aspirin or a NOAC. When you are on warfarin, recommended ranges vary according to the medical condition you have. Current guidelines recommend monthly INR monitoring.

Condition	INR Target and Range
Non-valvular atrial fibrillation (the most common reason)	2.0 - 3.0
Aortic Mechanical Valve	2.5 (Range 2.0 - 3.0)
Mitral Mechanical Valve	3.0 (Range 2.5-3.5)
Combined Aortic and Mitral Valve	3.0 (Range 2.5-3.5)
Pulmonic Valve	2.5 (Range 2.0 - 3.0)
Tricuspid Valve	3.0 (Range 2.5-3.5)
Combined Pulmonic and Tricuspid Valve	3.0 (Range 2.5-3.5)
Pulmonary Embolus	2.5 (Range 2.0 - 3.0)

References

[1]https://www2.gov.bc.ca/gov/content/health/practitioner-professional-resources/bc-guidelines/noac

[2] https://thrombosiscanada.ca/guides/pdfs/Mechanical_Valves.pdf

[3] https://thrombosiscanada.ca/guides/pdfs/PE.pdf