Communicating Diagnostic and Therapeutic Information to Patients

1. Communicating Diagnostic and Therapeutic Information to Patients Accounting for Lower Health Numeracy Christopher R. Carpenter, MD, MSc, Richard T. Griffey, MD, MPH, Dan Theodoro MD, June 2011 Journal Club Division of Emergency Medicine

2. Special Thanks to our guests • Mary Politi • Kim Kaphingst

3. Probability and Bayesian logic is confusing to everyone – not just those with low health numeracy Lay persons are not used to thinking beyond positive or negative test results or therapies recommended by their doctors. When clinicians consider test characteristics they often don’t consider these within the context of disease prevalence

4. Classic Question: A test correctly detects disease 95% of the time (sensitivity) in people with the disease and if negative effectively clears 90% of the patients in whom the disease is absent (specificity) If disease is present in 1 out of 1000 people (prevalence) what is the probability that a randomly chosen person who tests positive really has the disease?

5. Disease Status Symptom Present

6. Test characteristics:Validity (Accuracy) & Reliability Reliable, Not Valid Valid, Not Reliable Valid and Reliable

8. How Would You Communicate Risks & Benefits in the Emergency Department? • Need to find and appraise the evidence summary BEFORE the patient encounter • Here’s an example using tPA for acute ischemic stroke and the Wash U Journal Club archives @ http://emed.wustl.edu/em_journal_club.html

9. http://emed.wustl.edu/emjclub_July2009_TheEvidenceSupportsThrombolyticsStroke4.5Hours.htmlhttp://emed.wustl.edu/emjclub_July2009_TheEvidenceSupportsThrombolyticsStroke4.5Hours.html

10. PGY IV Critical Appraisal

11. Calculating Benefit Pictographs http://www.nntonline.net/visualrx/

12. From the Wash U PGY IV Critical Appraisal

15. What About Harm? http://www.nntonline.net/visualrx/

18. PGY INeedle Aspiration of PTX • Meta-analysis in 2007 identified only one high quality RCT upon which to base conclusions (Noppen 2002 – the PGY I article at that JC) • Noppen et al. demonstrated • No difference in immediate success rate • RR = 0.93 (95% CI 0.62-0.41) • No difference in early failure rate • RR = 1.12 (95% CI 0.59-2.13) • Lower hospitalization rates in aspiration • RR 0.52 (95% CI 0.36-0.75)

19. Case 1: PSP

20. Immediate Success Rate

21. Immediate Success Rate

22. Hospitalization Rate

26. PGY IICT for PE • PIOPED II provided the following test characteristics for PE protocol CT

27. Case 2: How accurate is CTA for PE? First risk stratification by Wells (prevalence): 56% low probability 38% intermediate probability 6% high probability So, we cannot PERC our patient but her Wells score is 0, so she is low probability for PE…. (sidestepping d-dimer testing…) Test characteristics: In general, when PE is present CTA detects it 83% of the time (Sensitivity) In general when CTA was negative it was correct 95% of the time (specificity) Among low prob patients though, a positive CTA indicates true disease only 58% of the time (PPV) and a negative CTA is correct 96% of the time (NPV).

28. Diagnostic CommunicationTwo Concepts • Test Accuracy • Disease Probability

29. Concept #1 Test Accuracy

30. Sensitivity = Has PE and CT shows it = Has PE and CT missed it

31. Specificity = Does not have PE and CT did not show a PE = Does not have PE but CT showed a PE

32. If we knew you did not have a PE before we tested you If we knew you had a PE before we tested you

33. Concept #2 Disease Probability

34. ?

35. Fagan Nomogram No PE on CT Low Risk ~3.6% mean probability of PE 3.6% pre-CT and CT no PE = 0.67% In other words, if 1000 patients with these odds of having a PE had a CT that did not demonstrate a PE, about 7 of them would still have a PE

36. Fagan Nomogram PE found on CT Low Risk ~3.6% mean probability of PE 3.6% pre-CT and CT with a PE = 42.3% In other words, if 1000 patients with these odds of having a PE had a CT that demonstrated a PE, about 423 of them would actually have a PE

38. Fagan Nomogram PE found on CT High Risk ~66.7% mean probability of PE 66.7% pre-CT and CT with a PE = 97.5% In other words, if 1000 patients with these odds of having a PE had a CT that demonstrated a PE, about 975 of them would actually have a PE

39. PGY IIISteroids to Prevent Recurrent Migraine • Critical appraisal provides the RR and 95% CI but not the control event rate so need to pull the original paper

40. Control Event Rate = [22 + 10 + 8 + 18 + 20 + 43 + 20] / 353 Control Event Rate = 141/353 Control Event Rate = 0.399

45. PGY IVHead CT After Blunt Trauma • 30 year old male in tornado-related building collapse without objective signs/symptoms of injury: Canadian Head CT Rule

46. Sensitivity = Has clinically important brain injury and Canadian Rule shows it = Has clinically important brain injury but Canadian Rule does not show it

47. Specificity = Does not have a clinically important brain injury and Canadian Rule does not show one = Does not have a clinically important brain injury but Canadian Rule suggests one

48. Fagan Nomogram Low-risk by Canadian Head CT Rule ~9% mean probability of significant injury before testing 9% pre-CT and Canadian Rule Low-Risk = 0.3% In other words, if 1000 patients with these odds of having a significant intracranial injury were low risk on the Canadian Head CT rules, about 3of them would still have a significant intracranial injury

49. Fagan Nomogram High Risk by Canadian Head CT Rule ~9% mean probability of significant injury before testing 9% pre-CT and Canadian Rule High-Risk = 16% In other words, if 1000 patients with these odds of having a significant intracranial injury were non-low risk on the Canadian Head CT rules, about 160 of them would actually have a significant intracranial injury