Practicing Evidenced-based medicine - Introduction

1. November 5, 2014 Matthew Tuck, MD Hospitalist, Veterans Affairs Medical Center Assistant Professor of Medicine, George Washington University Practicing Evidenced-based medicine - Introduction

2. 30 Years Ago… 1984 http://www.npr.org/2014/04/18/304140932/born-with-hiv-building-a-future

3. Reflection • Take a minute to think about… • What this story made you feel? • What this story made you think? • What questions you have after listening to this story?

5. 25 Years Later...

6. What if you didn’t keep up to date? Ann Intern Med. 2002;136(12):888-895.

7. Learning Objectives • Recognize the importance of practicing evidence-based medicine • Develop a systematic approach to practicing evidence-based medicine • Calculate absolute risk reduction, relative risk, relative risk reduction, and number needed to treat

9. Steps In Practicing EBM Ask Acquire Appraise Assess Apply

10. Steps in Practicing EBM • Ask: Convert the need for information into an answerable question. • Acquire: Track down the best evidence with which to answer that question. • Appraise: Critically appraise the evidence for its validity, impact, and applicability. • Apply: Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

11. The Answerable Question

12. Foreground Question TYPE OF QUESTION Background Question CLINICAL EXPERIENCE The nature of the question asked is critically experience dependent.

13. Back to Cristina and Chris…What questions do you have?

14. Questions • Background • Foreground

15. Back to Cristina and Chris… • Cristina and Chris are sexually active. Chris is HIV negative. They are wondering what treatments are available to help Chris from contracting HIV while maintaining a sexual relationship. What do you tell them?

16. Anatomy of a good clinical question: PICO-T

17. Back to Cristina and Chris… • Cristina and Chris are sexually active. Chris is HIV negative. They are wondering what treatments are available to help Chris from contracting HIV while maintaining a sexual relationship. • P = HIV serodiscordant couples • I = Antiretroviral prophylaxis • C = Standard medical care, placebo • O = HIV seroconversion

18. Steps in Practicing EBM • Ask: Convert the need for information into an answerable question. • Acquire: Track down the best evidence with which to answer that question. • Appraise: Critically appraise the evidence for its validity, impact, and applicability. • Apply: Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

19. Resources

20. Two Cardinal Rules of EBM • Not all evidence is created equal • A heirarchy of evidence guides clinical decision making • Evidence alone is never enough • Competent physicians balance risks and benefits of management strategies in the context of patient values and preferences

21. The Evidence Pyramid Experimental Observational

22. T – Type of Question/Type of Study • P = HIV serodiscordant couples • I = Antiretroviral prophylaxis • C = Standard medical care, placebo • O = HIV seroconversion

24. Steps in Practicing EBM • Ask: Convert the need for information into an answerable question. • Acquire: Track down the best evidence with which to answer that question. • Appraise: Critically appraise the evidence for its validity, impact, and applicability. • Apply: Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

25. You are now entering the world of Therapy Math!

26. How are Results Presented? • Absolute Risk = Event Rate • The number of people experiencing an event as a proportion of the total number of people in a population • Key Words • Divide if you see • Relative • Ratio • Subtractif you see • Absolute • Difference • Reduction

27. Example • 200 pre-schoolers • 100 pre-schoolers were randomized to drug X vs. 1o0 pre-schoolers to placebo for prevention of nose picking • 10 kids receiving drug X still picked their noses • 15 kids receiving placebo still picked their noses

28. What is the Risk of Nose Picking? • Drug X event rate = 10% • Placebo event rate = 15% • There are only two things we can do to these numbers • Subtract, or • Divide

29. Subtract Baseline Risk Experimental Risk • 15% - 10% = 5% • What does this number represent? • Absolute Risk Reduction (ARR) or Risk Difference • Arithmetic difference between 2 event rates • We refer to the risk of the adverse outcome in the control group as the baseline risk

30. Divide • 10% = 0.67 15% • What does this number represent? • Relative risk (RR) • Synonym = Risk Ratio • The proportion of the baseline risk that is still present when patients receive the experimental treatment Baseline Risk

31. Relative Risk Reduction • “What proportion of the baseline risk has been reduced by the experimental treatment?” • RRR = 1 – RR = 1 – 0.67 = 0.33 = 33% OR • RRR = ARR/baseline risk = 5%/15% = 0.33 = 33%

32. ARR vs. RRR… Why the Fuss? 50 25 10 5 2 1 Control Exper. Control Exper. Control Exper. ARR: RRR: 25% 5% 1% 50% 50% 50%

33. Number Needed to Treat (NNT) • NNT = 1/ARR Why? • If ARR = 5%... • Treating 100 people reduces outcome in 5; How many do I need to treat to help 1? • Answer = 20 100 5 ? 1

34. Back to Cristina and Chris… Practice!

35. Calculate ARR, RR, RRR, and NNT

36. Calculate ARR

37. Calculate ARR

38. Calculate ARR

39. Calculate ARR

40. Calculate ARR

41. Calculate ARR ARR = 52/1578 – 13/1576 = 0.025

42. Calculate RR, RRR RRR = 1 – 0.25 = 0.75

43. Calculate NNT NNT = 1/ARR = 1/0.025 = 40

44. Steps in Practicing EBM • Ask: Convert the need for information into an answerable question. • Acquire: Track down the best evidence with which to answer that question. • Appraise: Critically appraise the evidence for its validity, impact, and applicability. • Apply: Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

45. What would you tell Cristina and Chris?

46. Questions? Matthew Tuck, MD Matthew.Tuck@va.gov 202-745-8000 x53994