Short report: managing anticoagulation. Comparison of results at three primary care centres.

(1)

VOL 49: FEBRUARY • FÉVRIER 2003 Canadian Family Physician • Le Médecin de famille canadien 181

RESEARCH

Short report: Managing anticoagulation

Comparison of results at three primary care centres

Ross E.G. Upshur, ^MA, ^MD, ^MSC, ^FRCPC Christine Papoushek, ^PHARMD Denis Macdonald, ^MD, ^MBA, ^FRCPC Guilherme Dantas, ^MD, ^MHSC

E

vidence indicates that warfarin, a coumarin-type oral anticoagulant, is effective for preventing strokes and other thromboembolic complications in certain patients.¹ Its narrow therapeutic range means it can cause serious bleeding complications.² In managing anticoagulation, therefore, it is critical to follow a systematic process to ensure efficacy with minimal adverse effects.

In primary care, the most common indications for warfarin are atrial fibrillation, deep vein thrombosis, and prosthetic heart valves.

Since two of these indications require long- term prophylaxis, patients need continuous management and follow up.

Recent research, editorial opinion, and con- sensus statements suggest that specialized anticoagulation clinics manage patients better than traditional primary care services do.^3,4 Studies reported that patients in specialized clinics had better controlled anticoagulation, less frequent monitoring, and fewer adverse effects, and that staff had more experience in dose adjustments.

By definition, primary care providers are involved in continuity of care and clinical

management of several concomitant health conditions. Managing anticoagulation is just one of family practitioners’ many responsibili- ties. Their substantial role in managing anticoagulation will continue as the population ages and the indications for warfarin increase.

Hence, we need to evaluate how well primary care providers manage anticoagulation and establish benchmarks to ensure these physicians meet current standards of care.

This study was part of a clinic-wide initia- tive to define and deliver best practices in anticoagulation. It aimed to assess control of anticoagulation with warfarin in three primary care academic settings. It looked at patient demographics and characteristics and number of patients and time within target range on international normalized ratio (INR) tests. A literature search failed to identify any studies of anticoagulation in Canadian primary care settings.

METHOD

Patients receiving warfarin for more than 6 months were recruited from three sites: 193 from the Family Practice Units at Sunnybrook and Women’s College Health Sciences Centre (SWCHSC), 70 from the Ambulatory Care Centre at the Women’s College (WC) campus, and 75 from the Western Division of the University Health Network (TWH-UHN), where most primary care is provided by super- vised family practice residents.

During a 6-month retrospective audit of medical records, data were collected on demographics, medical diagnoses, duration of warfarin therapy, INR test intervals, INR results, and corresponding recommended doses of anticoagulant agents. One hospital laboratory at the WC and SWCHSC sites ran the INR tests; at the TWH-UHN site, most INR tests (79%) were run by one laboratory.

Data were entered into Excel spreadsheets.

Descriptive statistics were reported as counts Dr Upshur is Director of the Primary Care Research

Unit at Sunnybrook and Women’s College Health Sciences Centre (SWCHSC) and an Assistant Professor in the Departments of Family and Community Medicine and Public Health Sciences at the University of Toronto.

Ms Papoushek is a Pharmacist in the Family Practice Unit in the Department of Family and Community Medicine at Toronto Western Hospital, University Health Network. Dr Macdonald practises in the Department of Clinical Pathology at SWCHSC. Dr Dantas is a Research Associate in the Primary Care Research Unit at SWCHSC and at the Family Healthcare Research Unit in the Department of Family and Community Medicine at the University of Toronto.

This article has been peer reviewed.

Cet article a fait l’objet d’une évaluation externe.

Can Fam Physician 2003;49:181-184

(2)

182 Canadian Family Physician • Le Médecin de famille canadien VOL 49: FEBRUARY • FÉVRIER 2003

RESEARCH

Managing anticoagulation

RESEARCH

and percentages. Anticoagulation control was deter- mined by dividing the number of INR test results within therapeutic range (numerator) by the total number of tests performed (denominator). Out-of- range test results were calculated for both subtherapeutic and supratherapeutic values: INR < 2.0 or > 3.0 for atrial fibrillation and venous thrombosis, and < 2.5 or > 3.5 for prosthetic heart valves.⁵ No identifying information was abstracted from patients’ charts in keeping with ethics review board policies for chart audits.

RESULTS

A total of 338 patients from the three sites met the entr y criteria (Table 1). Patients were predomi- nantly elderly: 80% were older than 65. Most common indication for warfarin was atrial fibrillation.

Tests were ordered on average every 2 to 3 weeks.

Results within therapeutic range were reported as a mean of 58.6% (range 56% to 61%) across all three sites.

DISCUSSION

Oral anticoagulant therapy is managed mainly in primary care or community practice, despite inter- est in specialized anticoagulation clinics, patient self- monitoring, and patient self-management programs (including computer decision-support systems). This study demonstrated that primary care providers can manage anticoagulation within optimal ranges as well as some specialized anticoagulation clinics.

These findings are in contrast to those reported by Samsa and colleagues who found INR in-range values of 55% to 60% in a specialized anticoagulation service and only 34% to 47% in primary care settings.⁶ They concluded that anticoagulation services provided superior care, a claim reiterated in the literature. But the claim might well be unfounded, especially when primary care providers incorporate systematic, coordinated processes for monitoring their anticoagulation patients.

A recent review of articles on clinical trials indi- cated considerable variation (44% to 83%) in time Table 1. Characteristics of anticoagulation patients in three family practices: Mean frequency of INR tests every 6 months was nine at the Family Practice Unit, SWCHSC; eight at Toronto Western Hospital, UHN; and 10 at the Ambulatory Care Centre, WC campus, SWCHSC.

CHARACTERISTICS FAMILY PRACTICE UNIT, SWCHSC

% TORONTO WESTERN HOSPITAL,

UHN % AMBULATORY CARE CENTRE, WC CAMPUS, SWCHSC %

WOMEN 53 40 48

AGE (Y)

• <65 12 16 14

• 65-74 24 32 42

• >74 64 52 44

INDICATIONS FOR ANTICOAGULATION (N = 178) (N = 75) (N = 70)

• Atrial fibrillation 67 69 43

• Prosthetic heart valves 10 17 14

• Deep vein thrombosis, pulmonary embolism 9 5 21

• Cardiovascular accident, transient ischemic

attack 10 4 14

• Congestive heart failure, myocardial

infarction 0 3 3

• Other 4 1 4

CONTROL (N = 1535*) (N = 664*) (N = 705*)

• Supratherapeutic 20 16 17

• Therapeutic 61 56 59

• Subtherapeutic 19 28 24

INR—International normalized ratio, SWCHSC—Sunnybrook and Women’s College Health Sciences Centre, UHN—University Health Network, WC—Women’s College.

*N represents number of tests performed.

(3)

RESEARCH

spent in the therapeutic range, the primary outcome.

This might be explained by variations in how the primary outcome was calculated in the various studies.

Care of patients outside clinical trials results in generally lower rates (40% to 60%)⁷ of optimal control. This is likely a result of many factors related to patients, the disease, drugs, and physicians.

Fitzmaurice et al⁸ cite 60% as a credible benchmark reached by specialized anticoagulation clinics and cited in published clinical trials. Although 60% might be acceptable, we recognize that better results can be achieved.

The frequency of testing observed in our study is consistent with other studies that indicate primary care providers order INR tests more frequently than staff in specialized clinics do.⁹ One study showed that more frequent tests resulted in a higher percentage of time within therapeutic range as well as fewer adverse effects.⁴

The demographic characteristics of our patients are similar to those reported in the literature; typi- cal patients requiring anticoagulation are elderly and have atrial fi brillation.¹⁰ These elderly people are best managed in primary care because they often have comorbid diseases and greater need for close follow up and continuity of care.

Limitations

This study is limited by its descriptive nature and lack of clinical outcome analysis (effi cacy and adverse effects).

No formal statistical comparison between sites was con- ducted. The key to meeting optimal levels of anticoagulation appears to be a coordinated approach.

Also, our results, which are comparable to those of some specialized anticoagulation services, might refl ect the coordinated efforts at our practice sites.

In each setting, nurses and physicians collaborate in managing anticoagulation. No site employed decision aids in adjusting INR values. Our INR results are kept in a separate binder for ease of reference. If community physicians use similar procedures, they can obtain similar results in anticoagulation control.

There are, however, no studies describing primary care management of anticoagulation in Canada to validate this assumption. Such studies should be regarded as a research priority. The results of this descriptive study indicate that “acceptable” control of anticoagulation can be achieved in primary care.

Acknowledgment

We thank Ms Shari Gruman for revising the manuscript.

Dr Upshur is supported by a New Investigator Award from

the Canadian Institutes of Health Research and a Research Scholarship from the Department of Family and Community Medicine at the University of Toronto.

Contributors

Drs Upshur and Macdonald, and Ms Papoushek were involved in data collection and analysis, and in writing the article.

Dr Dantas was involved in data analysis and writing the article.

Competing interests None declared

Correspondence to: Dr R. Upshur, Primary Care Research Unit, Sunnybrook and Women’s College Health Sciences Centre, 2075 Bayview Ave, Room E-349, Toronto, ON M4N 3M5; telephone (416) 480-6100, extension 4753; fax (416) 480-4756; e-mail

[email protected] References

1. Segal J, McNamara R, Miller M, Powe N, Goodman S, Robinson K, et al.

Anticoagulants or antiplatelet therapy for non-rheumatic atrial fi brillation and fl ut- ter [Cochrane review]. In: The Cochrane Library. Issue 3. Oxford, Engl: Update Software; 2001.

2. Laupacis A, Albers G, Dalen J, Dunn MI, Jacobson AK, Singer DE. Antithrombotic therapy in atrial fi brillation. Chest 1998;114(Suppl 5):579-89S.

Editor’s key points

• Despite the advent of specialized anticoagulant clinics in a few urban centres, most anticoagulant monitoring is done by family physicians in community practice.

• This study showed that family physicians at three teaching units achieved 60% “in-therapeutic-range”

results for their anticoagulation patients, which was comparable to results in specialized clinics.

• The teaching units employed a simple but dedi- cated monitoring system to achieve these results.

Points de repère du rédacteur

• Malgré l’avènement de cliniques d’anticoagulation spécialisées dans quelques centres urbains, la surveillance de l’anticoagulation est effectuée en majeure partie par des médecins de famille prati- quant dans la communauté.

• Cette étude a révélé que les médecins de famille de trois unités d’enseignement ont obtenu pour leurs patients anticoagulés des valeurs à l’inté- rieur du domaine thérapeutique dans 60% des cas, ce qui se compare aux résultats obtenus par les cliniques spécialisées.

• Dans ces unités cliniques, ces résultats ont été obtenus grâce à un système de monitorage simple mais spécialisé.

(4)

RESEARCH

3. Chiquette E, Amato M, Bussey H. Comparison of an anticoagulation clinic with usual medical care: anticoagulation control, patient outcomes and health care cost. Arch Intern Med 1998;158:1641-7.

4. Ansell J, Hirsh J, Dalen J, Bussey H, Anderson D, Poller L, et al. Managing oral anticoagulant therapy. Chest 2001;119(Suppl 1):22-38S.

5. Hirsh J, Dalen J, Anderson DR, Poller L, Bussey H, Ansell J, et al. Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest 2001;119(Suppl 1):8-21S.

6. Samsa GP, Matchar DB, Goldstein LB, Bonito AJ, Lux LJ, Witter DM, et al. Quality of anticoagulation management among patients with atrial fibrillation: results of a review of medical records from two communities. Arch Intern Med 2000;160:967-73.

7. Abdelhafiz AH. A review of anticoagulation with warfarin in patients with nonvalvular atrial fibrillation. Clin Ther 2001;23:1628-36.

8. Fitzmaurice DA, Raftery JP, Bryan S. Policy dilemmas for oral anticoagulation management. Br J Gen Pract 2000;50(459):779-80.

9. Pell JP, McIver B, Stuart P, Malone DN, Alcock J.

Comparison of anticoagulant control among patients attend- ing general practice and a hospital anticoagulant clinic. Br J Gen Pract 1993;43(369):152-4.

10. Go AS, Hylek EM, Phillips KA, Chang Y, Henault LE, Selby JV, et al. Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study. JAMA 2001;285:2370-5

Short report: managing anticoagulation. Comparison of results at three primary care centres.

RESEARCH