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Alistair Howitt a Warders
Medical Centre, Tonbridge, Kent TN9 1LA, b Department of General
Practice, Guy's, King's And St Thomas' School of Medicine,
London SE11 6SP
Correspondence to: Dr Howitt
ajhowitt{at}warders.co.uk
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Abstract |
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Objective:
To determine the extent to which
implementation of an evidence based treatment, antithrombotic treatment
in atrial fibrillation, is possible in general practice.
Design:
Audit and qualitative study of patients with atrial fibrillation and an educational intervention for patients judged
eligible for antithrombotic treatment.
Setting:
South east England.
Subjects:
56 patients with a history of atrial fibrillation.
Interventions:
Assessment and interview to ascertain
patients' views on antithrombotic treatment.
Main outcome measures:
Number of patients receiving
antithrombotic treatment.
Results:
Out of 13 239 patients, 132 had a history of
atrial fibrillation of which 100 were at risk of thromboembolism. After
the study, 52 patients were taking warfarin. Of the remaining 48 patients (of whom 41 were taking aspirin), eight were too ill to
participate, 16 were unable to consent, four refused the interview, and
20 declined warfarin. Patients declining warfarin were inclined to seek
a higher level of benefit than those taking it, as measured by the
minimal clinically important difference. Qualitative data obtained
during the interviews suggested that patients' health beliefs were
important factors in determining their choice of treatment.
Conclusion:
Patients' unwillingness to take warfarin
seemed to be a major factor in limiting the number who would eventually take it.
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Key messages
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Introduction |
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Despite the efficacy of antithrombotic treatment in preventing stroke in patients with atrial fibrillation,1 community surveys report a low uptake of such treatment.2-4 Suggested explanations include general practitioners' reluctance to initiate and monitor treatment,5 practical difficulties in anticoagulating elderly housebound patients,6 and lack of authoritative guidelines.7 Yet a major part of the problem may relate to the proportion of patients eligible for treatment. Clinical trials, from which evidence for effectiveness is derived, usually exclude certain groups of patients, and trial conclusions might not be appropriate for these patients. Patients in clinical trials may also differ from others in their willingness to accept treatment.
The applicability of evidence based medicine to everyday general
practice therefore needs to take account of these constraints. The
potential scale of any success for an eligible group of patients will
be limited by exclusion of those patients for whom treatment would be
inappropriate and those who decline after their personal risk is
explained. We carried out such an exercise in a general practice, with
antithrombotic treatment in atrial fibrillation.
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Subjects and methods |
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Setting and subjects
We conducted our study in a predominantly urban practice in
South east England with 13 239 registered patients. We searched the
practice's computer database for patients for whom a diagnosis of
atrial fibrillation had been recorded and also for all patients who had
been prescribed digoxin. We then examined the paper records to confirm
the diagnosis.
Measures and procedure
Details of the patients' age, medical history, contraindications to warfarin, housing, and mobility were recorded. Current antithrombotic treatment was recorded as warfarin, aspirin, or
no treatment. For patients on warfarin, presence of an additional indication was recorded.
Educational intervention
We asked patients if they were aware that they were at
increased risk of stroke and if they were, to give an estimate of that risk.
2 for cross tabulations, independent samples
t test for two group comparisons, and analysis of variance
for multiple group comparisons.
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Results |
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We identified 132 patients with a history of atrial
fibrillation of whom 100 were judged eligible for warfarin. Of these, we excluded 16 who were unable to consent, eight who were too ill to
participate, and 16 who had other clinical indications for taking
warfarin. Of the remaining 60 patients, 56 (93%) consented to be
interviewed. There was no difference in age or duration of fibrillation
between patients attending for interview and the other 44 patients also
at risk who were not invited or declined to attend. These 44 patients
were more likely to have a history of stroke (
2 5.87, P<0.05), falls (Fisher's exact test, P<0.05), and frailty (Fisher's
exact test, P<0.01).
Before the study, 43 patients were taking warfarin, and subsequently 10 patients from the interview group started warfarin. Another seven patients who were taking no treatment started aspirin. One patient who had recently started warfarin to cover an unsuccessful cardioversion decided to switch to aspirin.
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None of the clinical sociodemographic variables or the severity measure of predicted annual stroke rate predicted which patients would start warfarin. Twenty nine patients (52%) agreed to echocardiography, but only one started warfarin because of the test result.
Patients' involvement
Most patients (61%, 34/56) were unaware that they were at
risk of stroke, and of those who were aware only two felt able to give
an annual estimate of the risk. Of the patients taking warfarin, eight
of 17 (47%) were not aware of the risk. Several patients were also
unaware that they had an irregular pulse.
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Discussion |
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The prevalence rates of atrial fibrillation reported here
are similar to those in recent studies from the United Kingdom, suggesting that identification of patients in our study had comparable efficiency.
2-4 11
But out of 132 patients with a
recorded history of atrial fibrillation
and 100 in whom it was judged
clinically appropriate
only 52 were taking warfarin at the end of
study. Of these, most were already taking it and only 10 started
warfarin
that is, even with careful case finding and follow up a large
proportion of patients with atrial fibrillation could not be changed to
an overtly more effective treatment.
Our study was conducted in only one practice and others might have different background prevalences of atrial fibrillation, concurrent illnesses, and patient responses. The proportion of patients taking warfarin before the intervention was higher than in other studies, 2-4 11 suggesting that the final proportion in our study was not unrepresentatively low. The fact that a half of eligible patients received warfarin after intensive exploration of best management for each patient suggests a major constraint on the uptake of evidence based medicine and a serious dilution of its potential impact.
Why was there such a small effect?
Four groups of patients can be identified out those judged
clinically eligible for warfarin: a small group already taking the drug
for other reasons; a group comprising those patients who were taking
warfarin solely for their fibrillation after the study; a group, about
a quarter of those eligible, who could not be offered treatment because
of other factors such as concurrent illness and dementia (as trial
protocols often exclude such patients it is clear that trials over
estimate the value of treatment in terms of the standard index of
number needed to treat); and a group who ultimately declined to be
assessed or to start treatment, even though clinically suited. So why
did some patients agree to take the drug while others declined?
Problems with implementation
Our study also puts into context the view that the problem
lies in the difficulty of changing doctors' behaviour to be more in
accord with current best evidence. Certainly, changing clinical
behaviour may not be easy but this must be seen in the light of other
significant barriers to implementing evidence based medicine in general practice.
namely, the patient's agreement to take the treatment. Had patients in this
study been expressly advised to start warfarin then perhaps the uptake
would have been greater. For example, general practitioners overrode a
decision to start warfarin in 18 out of 44 patients who were willing to
take it after being advised by a doctor involved in
a research project.2 But the approach reported here
suggests that a patient centred method, in which as many patients as
possible are given an active role in deciding their treatment, produces a less successful outcome regarding warfarin uptake but perhaps a
better one regarding the ethics of patient management. It might seem
ironic that it is patients who represent an important impediment to
implementation of effective treatment given that they apparently have
most to benefit, but without their support evidence based medicine is
likely to have only limited applicability in general practice.
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Acknowledgments |
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We thank Mr Chris Byrne for performing the echocardiography. Tunbridge Wells local research ethics committee approved the study.
Contributors: Our study derives from an MSc in general practice project carried out at Guy's, King's and St Thomas' School of Medicine. AH initiated the study design, analysed the data, and drafted the paper. DA contributed to the study design and the drafting of the paper. Both AH and DA will act as guarantors for the paper.
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Footnotes |
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Funding: NHS Executive-South Thames.
Competing interests: None declared.
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References |
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| 5. | Taylor F, Ramsay M, Voke J, Cohen H. Anticoagulation in patients with atrial fibrillation. GPs not prepared for monitoring anticoagulation. BMJ 1993; 307: 1493. |
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| 8. | Stroke Prevention in Atrial Fibrillation Investigators. Predictors of thromboembolism in atrial fibrillation. I. Clinical features of patients at risk. Ann Intern Med 1992; 116: 1-5. |
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O'Connell JE, Gray CS.
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(Accepted 31 March 1999)
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