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Man with gangrene of foot choose to amputate foot or

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Unformatted text preview: ngrene • From Pauker’s “Decision Analysis Service” at New England Medical Center Hospital, late 1970’s. • Man with gangrene of foot • Choose to amputate foot or treat medically • If medical treatment fails, patient may die or may have to amputate whole leg. • What to do? How to reason about it? Decision Tree for Gangrene Evaluating the Decision Tree 880 841.5 871.5 686 871.5 686 597 Decision Analysis: Evaluating Decision Trees • Outcome: directly estimate value • Decision: value is that of the choice with the greatest expected value • Chance: expected value is sum of (probabilities x values of results) • “Fold back” from outcomes to current decision. • Sensitivity analyses often more important than result(!) HELP System uses D.A. Intellectual Tools MC = .014 4000 Utility of operating minus Utility of not operating (∆u) 3000 MC = .010 MC = .014 2000 +1000 MC = .014 MC = .008 0 MC = .008 -1000 2000 Age 27 Age 57 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Probability that patient has appendicitis Effect of age patient and MC (mortality for appendicitis without operation) on the probability threshold (point of crossing zero ∆ u line) for decision to operate. Image by MIT OpenCourseWare. Adapted from Warner, Homer R. "Computer-assisted medical decision making." Academic Press, 1979. Warner HR, Computer-Assisted Medical Decision Making, Acad. Press 1979 Utility Analysis of Appendectomy 4: Computer Representation of Medical Knowledge 5000 Utility of operating minus Utility of not operating (∆µ) 4000 3000 2000 +1000 0 Salary -1000 35000 16000 8000 35000 16000 8000 2000 3000 0 0.1 0.2 0.3 Value of 1 day of good health 140 140 140 70 70 70 0.4 0.5 0.6 0.7 0.8 Probability of appendicitis 0.9 1.0 Effect of patient's salary and assumed value of one day of good health ($70 or $140) on decision to operate for appendicitis. Image by MIT OpenCourseWare. Adapted from Warner, Homer R. "Computer-assisted medical decision making." Academic Press, 1979. PROB OF APPENDICITIS A B C D E APPENDICITIS BY HISTORY REBOUND TENDERNESS IN RLQ PRIOR APPENDECTOMY IF C THEN EXIT WHITE BLOOD COUNT (WBCx100) TH/M3, LAST F PROB B A 620 90 G PROB F 43 18 9, 74 23 7, 93 18 11, 108 10 11, 121 16 13, 134 6 16, 151 5 16, 176 4 14 FVAL G UTILITY OF APPENDECTOMY IS ESTIMATED AS $--- A (A) AGE B SEX C (A) SALARY, GET A/365 D JOB, PERCENT ACTIVITY NEEDED E LE A,B F DLOS D 30 1, 65 2, 80 4, 90 1, 100 – 0 G DLOS D 40 1, 80 4, 95 5, 100 – 0 ...
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This document was uploaded on 03/20/2014 for the course EECS 6.872 at MIT.

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