Warfarin management in primary care

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Canadian Family Physician | Le Médecin de famille canadien}Vol 65: AUGUST | AOÛT 2019

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Top 5 recent articles read online at cfp.ca

1. Art of Family Medicine: Invisible work. Valuing emotional labour in family medicine (June 2019)

2. Clinical Practice Guidelines: Managing opioid use disorder in primary care. PEER simplified guideline (May 2019) 3. Clinical Review: Normal-weight central obesity. Unique hazard of the toxic waist (June 2019)

4. Clinical Review: Differentiating malignant melanoma from other lesions using dermoscopy (June 2019)

5. Commentary: Preparing family medicine trainees for the information revolution. Pearls, potential, promise, and pitfalls (June 2019)

Quality of warfarin management

I

read with interest the excellent article on warfarin management in Canada in the June issue of Canadian Family Physician.¹ I was particularly pleased to see Liu and colleagues make the important point that “conserv­

ative” 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,¹ which in general is more catastrophic (20% mortality, 59% disability).² This can be clearly seen in the classic graph by Hylek and Singer,² where the odds of ischemic stroke and intracranial hemorrhage are plotted against the patient’s international normalized ratio (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 might be helpful (eg, every 2 weeks) and the use of a reminder mecha­

nism (eg, an INR log app or a telephone call from a fam­

ily member or caregiver) might also be helpful. The good news with poor adherence and warfarin is that its long half­life (72 hours) gives the patient a “second chance.”

This is not the case with the direct oral anticoagulants, which have a shorter half­life (8 to 12 hours). For this reason, using a direct oral anticoagulant can put the forgetful patient at risk, as there is no routine blood test (like an INR or drug level) to tip us off.

Second, although Liu et al found that only 52.7% of INRs were within range in cases where atrial fibrillation, deep vein thrombosis, and pulmonary embolism were the indications for treatment, I am pleased that they rec­

ognized the potential for considerable improvement (eg, Sweden’s registry with 80.3% of INRs within therapeu­

tic range).¹ The disparity between Canada and Sweden demonstrates the great need for Canada to “pull up its socks.” The same technologies (point­of­care testing, computer decision support software, trained operators, patient self­management programs) are available to us as well. And these types of services do make a difference (eg, time in therapeutic range of 74% with New Zealand’s Community Pharmacy Anticoagulation Management Service program³; time in therapeutic range of > 80% with Germany’s self­management program⁴). 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 all­cause mortality (60% reduction),⁵ stroke and systemic embolism (49% reduction),⁵ and major hemorrhage (59% reduction),⁵ and commensurate cost reductions to our health care system.

Thank you, Liu and colleagues, for the excellent arti­

cle, and let’s work together in Canada to improve warfa­

rin management and achieve some “Viking” results!

—Murray Blakes Trusler MD MBA FCFP(LM) FRRMS Fairmont Hot Springs, BC

Competing interests

Dr Trusler is President of INR Online Canada Limited, a warfarin management software company.

References

1. Liu S, Singer A, McAlister FA, Peeler W, Heran BS, Drummond N, et al. Quality of warfarin management in primary care. Determining the stability of international normalized ratios using a nationally representative prospective cohort. Can Fam Physician 2019;65:416-25.

2. Hylek EM, Singer DE. Risk factors for intracranial hemorrhage in outpatients taking warfarin. Ann Intern Med 1994;120(11):897-902.

3. Harper P, Pollock D. Improved anticoagulant control in patients using home interna- tional normalized ratio testing and decision support provided through the Internet.

Intern Med J 2011;41(4):332-7.

4. Körtke H, Körfer R. International normalized ratio self-management after me- chanical heart valve replacement: is an early start advantageous? Ann Thor Surg 2001;72(1):44-8.

5. White HD, Gruber M, Feyzi J, Kaatz S, Tse HF, Husted S, et al. Comparison of out- comes among patients randomized to warfarin therapy according to anticoagulant control: results from SPORTIF III and V. Arch Int Med 2017;167(3):239-45.

Warfarin management in primary care

W

e read with interest the article entitled “Quality of warfarin management in primary care. Determining the stability of international normalized ratios using a nationally representative prospective cohort” by Liu et al.¹

Ten years ago, our community­based family health team implemented a pharmacist­led, weekly point­of­

care (POC) international normalized ratio (INR) clinic. All patients taking warfarin were booked into this clinic for a POC INR measurement and an immediate plan to manage results. In 2013, 2 of our (then) residents did a chart review of patients’ INR results over a 6­month period with usual care of INRs versus the POC INR clinic.² We found a substantial (12%) increase in time in therapeutic range with the POC model. Other advan­

tages 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 affect INR (such as new medications or illness). While more and more of our patients are tak­

ing direct oral anticoagulants, we continue to run our weekly POC clinic. Our clinic is pharmacist led; however,

Vol 65: AUGUST | AOÛT 2019 |Canadian Family Physician | Le Médecin de famille canadien

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CORRESPONDANCE

POC testing can also be done by physicians or nurses and nurse practitioners, and is a great learning opportu­

nity for medical residents.

This POC INR model is an alternative that could be consid­

ered to further improve INR management in the community.

—Deanna Telner MD MEd CCFP FCFP

—Jennifer Lake PharmD

—Gursharan Soor MD CCFP

—Jennifer Rossiter MD CCFP

—Babak Aliarzadeh MD MPH CCRA Toronto, Ont

Competing interests None declared References

1. Liu S, Singer A, McAlister FA, Peeler W, Heran BS, Drummond N, et al. Quality of warfarin management in primary care. Determining the stability of international normalized ratios using a nationally representative prospective cohort. Can Fam Physician 2019;65:416-25.

2. 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. Int J Fam Med 2013;2013:691454. Epub 2013 Dec 12.

Measuring visceral adiposity

A

fter reading the article “Normal­weight central obe­

sity. Unique hazard of the toxic waist” in the June issue of Canadian Family Physician,¹ I wanted to note that I find waist circumference to be an extremely inaccurate measure of visceral adiposity, which is located mostly in the anterior abdominal bulge, while “love handles” and subcutaneous adiposity cause very limited metabolic risk compared with visceral and ectopic fat. Short­² and long­term³ effects on the metabolic profile (including inflammatory markers, blood pressure, plasma lipid pro­

file, and insulin resistance) of large­volume liposuction (about 20% to 40% of excess body fat), mostly from the waist area, were no different after removing the large amounts of fat.

I think we should focus more on the anterior abdomi­

nal bulge than the whole waist circumference.

—Mohammed Abrahim MD CCFP(EM) Dip ABOM Milton, Ont

Competing interests None declared References

1. Bosomworth NJ. Normal-weight central obesity. Unique hazard of the toxic waist.

Can Fam Physician 2019;65:399-408 (Eng), e251-60 (Fr).

2. Klein S, Fontana L, Young VL, Coggan AR, Kilo C, Patterson BW, et al. Absence of an effect of liposuction on insulin action and risk factors for coronary heart disease.

N Engl J Med 2004;350(25):2549-57.

3. Mohammed BS, Cohen S, Reeds D, Young VL, Klein S. Long-term effects of large- volume liposuction on metabolic risk factors for coronary heart disease. Obesity (Silver Spring) 2008;16(12):2648-51. Epub 2008 Sep 25.

Response

I

thank Dr Abrahim for his comments in response to my article “Normal­weight central obesity. Unique haz­

ard of the toxic waist,” published in the June issue of Canadian Family Physician.¹ There is little doubt that waist circumference (WC) should be a very unreliable measurement for the proportion of visceral to subcu­

taneous (SC) fat, and there is even no universal con­

sensus surrounding where to measure or what the

measurement cutoff value for risk should be. In spite of this, the anthropometric measures of abdominal obe­

sity have surprisingly high correlations with mortality.

Perhaps if we had simple and reliable ways of measur­

ing only the high­risk visceral component, the associa­

tion would be even stronger.

Several studies using computed tomography have shown that the ratio of visceral fat to SC fat is an inde­

pendent predictor of cardiac events and mortality.^2,3 This ratio is likely to be larger in the lean centrally obese than in the globally obese who have a much thicker abdomi­

nal SC fat layer, lending some credence to the possibility that SC fat might offer some protection against the rav­

ages wrought by visceral fat.

In lean centrally obese people the SC fat partition would be expected to be a smaller part of the waist cir­

cumference component than in the globally obese. It has been shown that, as obesity increases, the infiltra­

tion of macrophages and inflammatory activity increases markedly in visceral fat,⁴ perhaps helping to explain why the large contribution of subcutaneous fat to WC meas­

urement does not greatly diminish the value of this met­

ric in predicting cardiometabolic events.

It would seem that no matter how inexact WC measure­

ment is, it consistently identifies mortality risk better than body mass index does. A pragmatic metric such as waist­

to­height ratio then allows a busy family physician to flag this risk if WC exceeds half the patient’s height. This is at least equally important if the person is not globally obese.

—N. John Bosomworth MD CCFP FCFP Vancouver, BC

Competing interests None declared References

1. Bosomworth NJ. Normal-weight central obesity. Unique hazard of the toxic waist.

Can Fam Physician 2019;65:399-408 (Eng), e251-60 (Fr).

2. Ladeiras-Lopes R, Sampaio F, Bettencourt N, Fontes-Carvalho R, Ferreira N, Leite- Moreira A, et al. The ratio between visceral and subcutaneous abdominal fat assessed by computed tomography is an independent predictor of mortality and cardiac events. Rev Esp Cardiol (Engl Ed) 2017;70(5):331-7. Epub 2016 Oct 17.

3. Lee SW, Son JY, Kim JM, Hwang SS, Han JS, Heo NJ. Body fat distribution is more predic- tive of all-cause mortality than overall adiposity. Diabetes Obes Metab 2018;20(1):141-7.

4. Harman-Boehm I, Blüher M, Redel H, Sion-Vardy N, Ovadia S, Avinoach E, et al.

Macrophage infiltration into omental versus subcutaneous fat across different populations: effect of regional adiposity and the comorbidities of obesity. J Clin Endocrinol Metab 2007;92(6):2240-7. Epub 2007 Mar 20.

Correction

I

n the article “Differentiating malignant melanoma from other lesions using dermoscopy,” which appeared in the June issue of Canadian Family Physician,¹ the authors were listed in the incorrect order. The correct order is as follows:

Ahmed Mourad Robert Gniadecki MD PhD DMSci

The authors apologize for this error and any confu­

sion it might have caused. The online version has been corrected.

Reference

1. Gniadecki R, Mourad A. Differentiating malignant melanoma from other lesions using dermoscopy. Can Fam Physician 2019;65:412-4 (Eng), e261-3 (Fr).