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Lecture Decision analysis

This document includes these contents: What is decision analysis, decision trees, how they work, a bit on economics, critical appraisal of decision analysis, an example of some software,. Invite you to result. | Decision Analysis Dr M G Dawes Centre for Evidence Based Medicine Contents What is Decision Analysis? Decision Trees How they work Critical Appraisal of Decision Analysis A bit on economics An example of some software What is Decision Analysis? Urinary Tract Infection Patient presents with symptoms What would happen if you opted for one path in preference to another On what basis would you assess outcome How does one start? List all the options and display: Commonly accepted format is a tree diagram. UTI Decision Node Treat Don’t Treat Decision data UTI Chance Node Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 Result 0.9 is better than 0.2 UTI Chance Node Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 Add reality to probability scores Cost of tests Cost of treatment Days lost from work Cost of re attending clinician Multiply the probabilities by the costs Cost Data UTI Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 2 9 2 9 Costs Rollback Costs UTI Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 2 9 2 9 (2*0.9) + (9*0.1)=2.7 (0.2*2)+(0.8*9)=7.6 Results More people get better (90 % vs 20%) It is cheaper (2.70 vs 7.60) What does the patient think? Utilities How would you feel? QALYs Quality adjusted life year QALY’s From Alastair Gray Time Trade Off Method (to assess utility of a health state) You have arthritis (severe - unable to walk to shops – need a buggy – in pain most of the time) and are aged 48 Choose between living with arthritis until 80 or living in perfect health for a shorter length of time eg 50 60 70 If 70 – 65 67 69 71 73 75 Etc until chosen a year Time Trade Off Utility is 1- (number of years willing to give up/(80-current age) If age selected was 75 Utility = 1-(80-75)/(80-48) = 0.84 The better your health the less the years you give up Trade Off vs Age Utilities UTI Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 9 2 9 2 Utilities . | Decision Analysis Dr M G Dawes Centre for Evidence Based Medicine Contents What is Decision Analysis? Decision Trees How they work Critical Appraisal of Decision Analysis A bit on economics An example of some software What is Decision Analysis? Urinary Tract Infection Patient presents with symptoms What would happen if you opted for one path in preference to another On what basis would you assess outcome How does one start? List all the options and display: Commonly accepted format is a tree diagram. UTI Decision Node Treat Don’t Treat Decision data UTI Chance Node Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 Result 0.9 is better than 0.2 UTI Chance Node Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8 Add reality to probability scores Cost of tests Cost of treatment Days lost from work Cost of re attending clinician Multiply the probabilities by the costs Cost Data UTI Treat Don’t Treat better Not better better Not better 0.9 0.1 0.2 0.8