1. Decision Science Brian J Wells, MD, PhD

2. Wake Forest Baptist Medical Center Humans are poor decision makers when chance is involved and we frequently fail to recognize chance. 2

3. Wake Forest Baptist Medical Center Humans use intuition and heuristics to simplify complex decision making 3

4. Wake Forest Baptist Medical Center Types of Cognitive Errors Made by Clinicians Availability Error – Over/underestimation of the probability of a diagnosis based on recent / memorable cases. Representation Error – Clinician jumps to the conclusion that patient has disease X because symptoms match the “textbook example.” Premature Closure – reaching a final diagnosis before all relevant information has been processed. Anchoring – Clinging to diagnoses that should be reconsidered based on new information Confirmation bias – cherry picking results that confirm assumptions Attribution errors - sterotypes

5. Wake Forest Baptist Medical Center Factors in Decision Making Stakes Different points of view Urgency Cost Utility Personal preference 5

6. Wake Forest Baptist Medical Center Utility – Preference for a particular health state (ranges from 0-1) Direct Measurement Time Trade Off Standard Gamble Indirect Measurement SF-36 EuroQoL 6

7. 7

9. Wake Forest Baptist Medical Center QALY 1.0 0.0

10. Wake Forest Baptist Medical Center Items needed to conduct a Cost Effectiveness Analysis Probabilities Potential Outcomes Length of time Cost Utilities 10

11. 11

12. Wake Forest Baptist Medical Center Limitations of Cost effectiveness analyses Personal preferences Inadequate data on utilities Complicated analyses that depend on many assumptions. Hard to replicate Depends on perspective One choice is generally not dominant. Differing opinions about what 1 year of life in perfect health is worth No CEA exists 12

13. Wake Forest Baptist Medical Center Patient with a Pulmonary Embolism LIST OF SYMPTOMS 1.Numbness on the left side of her body 2.Shortness of breath

14. Wake Forest Baptist Medical Center The probability that two events will both occur can never be greater than the probability that each will occur individually. 14

15. Wake Forest Baptist Medical Center Clinical Decision Support Systems (CDSS) 15

16. Wake Forest Baptist Medical Center 5 Rights of CDS - Osheroff 1.Right Information 2.Right Person 3.Right Format 4.Right Channel 5.Right Time 16

17. 17

19. Wake Forest Baptist Medical Center Specificity The probability that a test rules out a disease when the disease is truly absent 19

20. Wake Forest Baptist Medical Center HPI –Bob is a 45 year old white male who works as a systems analyst for a local bank. Bob recently underwent a medical exam for a new life insurance policy. The immunoassay screening test for HIV was positive. The physician assigned by the insurance company says that the test has a specificity of 99% and therefore there is a 99% chance that Bob has HIV. 20

21. Wake Forest Baptist Medical Center ROS CON: No F/C/S, No wt loss, normal energy SOCIAL – No tobacco or alcohol, No history of IV drug use. Heterosexual. Married to Rita for 18yrs and has 3 young children. A one-time extramarital affair with an ex-girlfriend about 10 years, otherwise monogamous. PAST MEDICAL HX – No history of blood transfusions 21

22. Wake Forest Baptist Medical Center Bayes Theorem 22

23. Wake Forest Baptist Medical Center Positive Predictive Value (PPV) – Prevalence matters! Does not have HIVHas HIV Negative Immunoassay98,9920 Positive Immunoassay1,0008 99,9928 23 PPV = 8/1008 = 0.08 (8%) Pre test probability = 0.00008 (0.008%) Post test probability = 0.08 (8%)

24. Wake Forest Baptist Medical Center Level of Evidence Systematic Review of RCTs RCT Cohort Study Case Control Study Case Series Expert Opinion 24 Most Least

25. 25

26. 26

28. Wake Forest Baptist Medical Center Door 1Door 2Door 3 Sample Space

29. Wake Forest Baptist Medical Center Door 1Door 2Door 3 Sample Space StaySwitch WinLose Win LoseWin LoseWin Lose Win LoseWin LoseWin Lose

30. 1

31. 31 2

32. 32 3

33. 33 4

34. 34 5

35. 6

36. 36 7

37. 37 8

38. 38 9

39. 39 10

40. 40 11

41. 41 12

42. 42 13

43. 43 14

44. 15

45. 45 16

46. 17

47. 18

48. 48 19

49. 49 20

50. 50 21

51. 51 22

52. 23

53. 24

54. 25

55. 26

56. 56 27

57. 57 28

58. 29

59. 59 30

60. 60 31

61. 61 32

62. 62 33

63. 63 34

64. 64 35

65. 65 36

66. 66 37

67. 67 38

68. 68 39

69. 69 40