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Protheroe and colleagues in Bristol constructed a decision tree for this decision, using evidence-based probabilities for varying levels of risk factors and individual patient's utilities for 4 outcome states (see Attributes). They found that the optimal option often differed from that recommended by guidelines and in practice. The Annalisas below distinguish the disutility of Major and Minor side effects of warfarin, but otherwise replicate their analysis. Average weightings are used for illustrative puposes and as default, but remember that the aim of Annalisa in the clinical situation is to facilitate patient-specific preference based analyses , not arrive at group or population conclusions. - Functional dependence following stroke
- Major side effects from Warfarin
- Minor side effects from Warfarin
- Stroke without functional consequences
- Warfarin anticoagulation
- no Warfarin anticoagulation
Annual Probabilities of stroke provided for 2 age group (65-75 and over 75) and 4 Risk Factor groups (0, 1 or more, CHF and 0, CHF and 1 or more), where the RF are Diabetes and Hypertension, but not Congestive Heart Failure. Relative Risk Reduction from Warfarin = 68%. Probability of Functional Dependence (FD) from stroke = 35%. Probability of Major Side Effects from Warfsrin = 1.1%, of Minor SE 11.1%. Slide 1 is for a 65-75 yo with 0 RF, slide 2 for a 65-75 yo with CHF and 1 or more RFs. Utilities were elcited by Time Trade-off method. Deductions from 1: - any SE = .2 [We enter .4 for major and .1 for minor]
- stroke without FD consequences = .3;
- FD = .9
As impled by  Ratings and Weightings J Protheroe, T Fahey, AA Montgomery, TJ Peters (2000) The impact of patients' preferences on the treatment of atrial fibrillation: observational study of patient based decision analysis BMJ 320: 1380-1384 The purpose of presenting an Annalisa version of a study conducted using another DA method (such as a Decision Tree) is to summarise and present the analysis in a simple and attractive one-screen format for a large audience - and to permit the interested viewer to download the .alt file and interact with the Weightings and Ratings to determine the effect of changes on the Scores. Alternatively the .alt file may be used as a 'starter' for a new analysis. No opinion is expressed or implied in regard to the merits of the study on any criterion.
Download alt file 65-75, 0 RF here Download alt file 65-75, CHF+1 or more RF here
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