Elsevier

The Lancet

Volume 355, Issue 9208, 18 March 2000, Pages 956-962
The Lancet

Articles
Decision analysis and guidelines for anticoagulant therapy to prevent stroke in patients with atrial fibrillation

https://doi.org/10.1016/S0140-6736(00)90012-6Get rights and content

Summary

Background

Clinical guidelines are needed on whether or not to use anticoagulant therapy to prevent stroke in patients with non-valvular atrial fibrillation. We did a Markov decision analysis to model decision-making with regard to warfarin treatment in patients with atrial fibrillation, and used the model to develop evaluative guidelines.

Methods

The decision analysis involved a systematic literature review supplemented by patients' estimates of the quality of life associated with different states of health, secondary analysis of stroke-registry data, and estimation of service costs; it also incorporated a sensitivity analysis. The derived guidelines were subsequently applied to a cohort of patients with atrial fibrillation.

Findings

We constructed decision tables for 12 age and sex groups. For most risk combinations, warfarin treatment would have decreased health-care costs and increased quality-of-life years, although the clinical decision was sensitive to patients' preferences and to the estimate of warfarin's effectiveness. 97% of women with atrial fibrillation older than 75 years, and 69% aged 65–74 would have been recommended for treatment; for men, the corresponding figures would have been 75% and 53%. With the upper quartile for the loss of quality of life associated with being on warfarin treatment (1·00), all but two of the 116 patients without contraindications would have been treated, whereas with the lower quartile (0·92), only 27 of 116 would have been treated.

Interpretation

Decision analysis is useful in the incorporation of complex probabilistic data into informed decision-making, the identification of factors influencing such decisions, and the subsequent development of evaluative guidelines.

Introduction

Non-valvular atrial fibrillation increases the risk of stroke,1 but anticoagulant therapy decreases this risk by about two thirds.2, 3, 4 However, few clinicians have acted on this evidence5—a finding that is reflected in the underuse of anticoagulant therapy in patients with atrial fibrillation.6, 7, 8, 9

Clinical guidelines can change medical practice and improve health.10 Previous studies have shown not only demand for guidelines in this area,11 but also variation in the content and implications of those available.12 Guidelines have been classified into a hierarchy ranging from informal and formal consensus guidelines, through evidence-based guidelines, to evaluative guidelines.13 The evaluative method may offer the most comprehensive approach since it incorporates data on quality of life and allows explicit quantitative comparison of the benefits and risks of different therapies. However, it has not been widely used.14

Decision analysis permits explicit quantitative comparison of the benefits and risks of different therapies. Previous use of decision analysis has taken a rigorous approach to the synthesis of data from randomised controlled trials, but has not used similarly careful techniques in the assessment of epidemiological evidence,15 nor has it made the critical step of translating the results of this synthesis into practical tools for making clinical decisions.16, 17

We used a Markov decision analysis to model decision-making about warfarin treatment in patients with atrial fibrillation. The analysis included a systematic literature review followed by the development of evaluative guidelines. We then applied the guidelines to a cohort of patients with atrial fibrillation.8

Section snippets

Data acquisition

We did a systematic search of published studies on: effectiveness of anticoagulant and antiplatelet therapies; natural history and risk of stroke in patients with atrial fibrillation; adverse effects of warfarin; utility of relevant health states; and costs of treatment. Titles and abstracts were read, and potentially relevant articles retrieved for full appraisal. Our basic tools were MEDLINE and BIDS, the Cochrane Search Strategies,18, 19 and, for appraisal, the Evidence-Based Medicine

Data acquisition

There were six randomised, controlled trials of warfarin anticoagulation,3, 31, 32, 33, 34, 35 and a pooled analysis of five of them.2 One trial33 reported only an on-treatment analysis and was excluded. Four were not double-blind.3, 31, 33, 34 The pooled study2 analysed the data by intention-to-treat, which overcame the problem of on-treatment results, but included trials that were not double-blind. The two double-blind trials of warfarin and placebo32, 35 were terminated early, and only one

Discussion

We have shown that a Markov decision-analysis model can clarify the factors that affect clinical decision on anticoagulation. Decision analysis explicitly quantifies uncertainty—eg, we showed that the decision on whether to anticoagulate is sensitive to the estimate of the effectiveness of warfarin, which itself is available as a point measure with attendant uncertainty in the form of confidence intervals around this estimate. The incorporation of a patient's preference also makes explicit the

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