Quality of warfarin management in primary care: Determining the stability of international normalized ratios using a nationally representative prospective cohort

Sharon Liu; Alexander Singer; Finlay A. McAlister; William Peeler; Balraj S. Heran; Neil Drummond; Donna P. Manca; G. Michael Allan; Christina Korownyk; Michael R. Kolber; Michelle Greiver; Scott R. Garrison

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RE: Quality of warfarin management in primary care
Deanna Telner, Jennifer Lake, Gursharan Soor, Jennifer Rossiter and Babak Aliarzadeh

Published on: 24 June 2019
RE: Quality of Warfarin Management
Murray Blakes Trusler

Published on: 21 June 2019

Published on: (24 June 2019)

RE: Quality of warfarin management in primary care
Deanna Telner, Family Physician, South East Toronto Family Health Team, Department of Family and Community Medicine, University of Toronto
Other Contributors:
Jennifer Lake, Pharmacist

Gursharan Soor, Family Physician

Jennifer Rossiter, Family Physician

Babak Aliarzadeh, Biostatistician
We read with interest the article entitled “Quality of warfarin management in primary care” by Liu et al.

Ten years ago, our community-based FHT implemented a pharmacist- led, weekly point-of-care (POC) INR clinic. All patients on warfarin were booked into this clinic for a POC INR, and immediate plan to manage results. In 2013, two of our (then) residents did a chart review of patients INR results over a 6-month period with usual care of INR versus POC clinic (1). We found a significant (12%) increase in TTR with the POC model. Other advantages of this model included eliminating the lag-time between results and management, and providing an opportunity for patients to discuss any new medical issues that could impact INR (such as new medications or illness). While more and more of our patients are on direct oral-anti-coagulants (DOAC), we continue to run our weekly POC clinic. Our clinic is pharmacist-led, however, POC can also be done by physicians or nurse/nurse practitioners, and is a great learning opportunity for medical residents.

This POC INR model is an alternative that could be considered to further improve INR management in the community.

1. Rossiter J, Soor G, Telner D, Aliarzadeh B, Lake J. A pharmacist-led point-of-care INR clinic: Optimizing care in a family health team setting. International J Fam Med 2013#691454

Competing Interests: None declared.
Published on: (21 June 2019)

RE: Quality of Warfarin Management
Murray Blakes Trusler, Family Physician, Retired: Assistant Professor, Family Medicine, Queen's University; Associate Professor, Family Medicine, NOSM
I read with interest your excellent article on warfarin management in Canada. I was particularly pleased to see you make the important point that “conservative” management of warfarin (underdosing in an effort to avoid hemorrhage) is a potentially dangerous practice and leads to a greater risk of stroke than hemorrhage, which in general is more catastrophic (20% mortality, 60% major disability). This can be clearly seen in the classic graph by Hylek et al1, where the odds of ischemic stroke and ICH are plotted against the patient’s INR.

Although, this situation is sometimes deliberate on the part of the physician (worried about a major bleed), it is often due to poor adherence on the part of the patient. Elderly minds become forgetful as we all know. In this situation, more frequent testing may be helpful (e.g. q 2 weeks) and the use of a reminder mechanism (e.g. INR Log App or a phone call from a family member/care giver may also be helpful). The good news with poor adherence and warfarin is that its long half-life (72 Hours) gives the patient a “second chance”. This is not the case with the DOAC’s which have a shorter half-life (8-12 hours). For this reason, using a DOAC can put the forgetful patient at risk as there is no routine blood test (like an INR or drug level) to tip us off.

Secondly, although in the case of AF, DVT and PE as the indication for treatment, only 52.7% of INR’s were within range, I am pleased that you recognized the potential...
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I read with interest your excellent article on warfarin management in Canada. I was particularly pleased to see you make the important point that “conservative” management of warfarin (underdosing in an effort to avoid hemorrhage) is a potentially dangerous practice and leads to a greater risk of stroke than hemorrhage, which in general is more catastrophic (20% mortality, 60% major disability). This can be clearly seen in the classic graph by Hylek et al1, where the odds of ischemic stroke and ICH are plotted against the patient’s INR.

Although, this situation is sometimes deliberate on the part of the physician (worried about a major bleed), it is often due to poor adherence on the part of the patient. Elderly minds become forgetful as we all know. In this situation, more frequent testing may be helpful (e.g. q 2 weeks) and the use of a reminder mechanism (e.g. INR Log App or a phone call from a family member/care giver may also be helpful). The good news with poor adherence and warfarin is that its long half-life (72 Hours) gives the patient a “second chance”. This is not the case with the DOAC’s which have a shorter half-life (8-12 hours). For this reason, using a DOAC can put the forgetful patient at risk as there is no routine blood test (like an INR or drug level) to tip us off.

Secondly, although in the case of AF, DVT and PE as the indication for treatment, only 52.7% of INR’s were within range, I am pleased that you recognized the potential for major improvement (e.g. Sweden’s registry with 80.3% of INR’s within therapeutic range). The disparity between Canada and Sweden demonstrates the great need for Canada to “pull up its socks”. The same technologies (point of care testing, computer decision support software, trained operators, patient self-management programs) are available to us as well. And they do make a difference (e.g. New Zealand’s CPAMS program 2 – TTR 74%, Germany’s self-management program3 – TTR >80%). And they do need wide adoption in our country. The cost of missing the opportunity to emulate Sweden’s performance is huge in terms of all-cause mortality – 60% reduction4, stroke and systemic embolism – 49% reduction4, major hemorrhage – 59% reduction4 and commensurate cost reductions to our healthcare system.

Thank you for your excellent article and let’s work together in Canada to improve warfarin’s management and achieve some “Viking” results!

Ref.

1. Hylek EM, Singer DE. Risk factors for intracranial hemorrhage in outpatients taking warfarin. Ann Intern Med. 1994 Jun 1;120(11):897-902.
2. Harper P, Pollock D. Improved anticoagulant control in patients using home international normalized ratio testing and decision support provided through the internet. Intern Med J. 2011 Apr;41(4):332-7.
3. Kortke et al. Ann. Thor. Surg. 2001, 72(44-48).
4. White HD, Gruber M, Feyzi J et al. Arch. Int. Med. Vol. 167 February 12, 20017. Results from Sportif III and Sportif V.
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Competing Interests: President INR Online Canada Limited. Warfarin management software company.