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Best Tests November 2006

Including: INR PDF
Full colour PDF of ‘best tests’ November 2006.
 Printer friendly PDF.

‘INR testing’ reminder……

Patient education

Patient education is an important component of achieving good INR levels. Patients who are well informed and understand what they are doing are more likely to benefit from treatment. Patient information for those starting warfarin and the “red book” are good resources for patients.


Warfarin should be prescribed by brand name.
Use only 1 mg tablets during initiation to minimise confusion.
Use labelling to highlight the importance of INR monitoring - labels such as ‘PRN’ or ‘as required’ may confuse.

Warfarin therapy must be detailed in the patient notes

The patient notes should contain the following: the patient is on warfarin, condition for which prescribed, target INR range, planned duration of treatment, brand of warfarin. An alert which appears whenever the clinical records of a patient on warfarin are accessed may be a useful tool. For details on setting up an alert see appendix 4 in the bpacnz INR testing guide.

Managing INR levels

A reasonable standard of warfarin therapy is an INR within the target range 60% of the time. Once stable the rate of INR testing can be extended to 4 to 6 weekly in most people.Changes in the INR level in a usually stable patient may be due to: non-adherence to dosage regimen, drug interactions (pharmaceutical or herbal), major changes in diet or alcohol intake, or concurrent disease. For minor fluctuations in (the) INR, changes in weekly doses are usually not required. For more significant fluctuations, use a standard guide to assist dose modification.