Evidence Based Dentistry: Statistics

1. Evidence Based Dentistry: Statistics Critical Appraisal Skills depend on understanding the relationship between study design and levels of evidence Al Best, PhD Director of Faculty Research Development Perkinson 3100B ALBest@VCU.edu

2. Evidence-Based Dentistry • Derek Richards "Is it worth reading this paper?" Evidence-based Dentistry (2000) 2, 50-52. Integration of: Best Evidence Available Clinical Judgment Patient Values/Circumstances

3. Critical Appraisal Skills • Are the results of the study valid? • What are the results? • Will the results help locally? Best Evidence Available

4. Review • Yeudall and Gordon • EBD Methodology / Practice • PICO PECO questions • Types of Research and Study Design • Levels of Evidence

5. EBD Methodology / Practice EBD Methodology / Practice 1. ASK an answerable question ASK 2. SEARCH for the evidence ACQUIRE 3. EVALUATE the evidence APPRAISE 4. APPLY the evidence APPLY 5. EVALUATE the outcome ASSESS

6. Niederman, R. et al. JADA 2011;142:4:364-367 Figure The evidence pyramid displays the quality of evidence according to type of study. “Quality” refers to the likelihood of predicting what would occur in one’s own practice (and the least probability of bias). Guidelines explicitly based on this evidence pyramid offer clinicians a simplified mechanism for obtaining and potentially using the knowledge identified in this pyramid. Conversely, the lowest level of evidence, with the least likelihood of predicting what would occur in one’s practice (and the highest probability of bias), can provide useful background information (such as laboratory and animal studies, cross-sectional epidemiologic studies, and expert opinion or narrative reviews). “Filtered information” is so-called secondary research. These reports systematically search for, critically appraise, distill and present the results of primary research, called here “unfiltered information.” Adapted from Harvey Cushing/John Hay Whitney Medical Library, Yale University.

7. Niederman, R. et al. JADA 2011;142:4:364-367 • “a significant evolution from • intuition-based care, • to experience-based care, • to evidence-based care. • The intuition, experience and now evidence on which we base our care are simply steps on the evidence pyramid…” pubmed/21454838 or JADA

8. Niederman, R. et al. JADA 2011;142:4:364-367 • “Those who are proponents of experience-based care to the exclusion of evidence-based care may be surprised to find that they place themselves and their patients at risk, clinically and legally. • Clinically, it is unlikely that the majority of clinicians are implementing the current best evidence.”

9. Niederman: “Clinically, it is unlikely that the majority of clinicians are implementing the current best evidence. • “If they were, there would be little variation in care. But this is not the case. In the 1980s, Wennberg16 found that dental extractions were among the most variable causes of hospital admissions (a 10-fold range). … • Dental school faculty members also demonstrate substantial variation in the care planned and provided to patients.18 • Estimates of clinical variation are substantial. One estimate indicates that 30 to 40 percent of patients do not receive care according to the current best evidence, and 20 to 25 percent of the care provided is not needed or is potentially harmful.19”

10. Niederman, R. et al. JADA 2011;142:4:364-367 Figure The evidence pyramid displays the quality of evidence according to type of study. “Quality” refers to the likelihood of predicting what would occur in one’s own practice (and the least probability of bias). Guidelines explicitly based on this evidence pyramid offer clinicians a simplified mechanism for obtaining and potentially using the knowledge identified in this pyramid. Conversely, the lowest level of evidence, with the least likelihood of predicting what would occur in one’s practice (and the highest probability of bias), can provide useful background information (such as laboratory and animal studies, cross-sectional epidemiologic studies, and expert opinion or narrative reviews). “Filtered information” is so-called secondary research. These reports systematically search for, critically appraise, distill and present the results of primary research, called here “unfiltered information.” Adapted from Harvey Cushing/John Hay Whitney Medical Library, Yale University.

11. "The Toothpuller", ascribed to Caravaggio (1571-1610).

14. My goals for you Be able to answer four questions: • Based on the study design, what is the level of evidence? • How were threats to validity addressed? • Based on the goals of the study, How do you describe the results? • To justify the conclusions, were comparisons done appropriately?

15. Example • A 63 year old male patient has a heart murmur caused by an aortic valve prolapse and is scheduled for tooth cleaning. • Do you prescribe an antibiotic to be taken before dental treatment?

16. Google: does tooth cleaning cause bacteremia? Bacteremia can have several consequences. The immune response to the bacteria can cause sepsis and septic shock, which has a relatively high mortality rate.

17. Meta Cognition • “a significant evolution from • intuition-based care, • to experience-based care, • to evidence-based care. • The intuition, experience and now evidence on which we base our care are simply steps on the evidence pyramid…” Niederman, R. et al. JADA 2011;142:4:364-367

18. Example • A 63 year old male patient has a heart murmur caused by an aortic valve prolapse and is scheduled for tooth cleaning. • Do you prescribe an antibiotic to be taken before dental treatment?

19. EBD Methodology / Practice EBD Methodology / Practice 1. ASK an answerable question ASK 2. SEARCH for the evidence ACQUIRE 3. EVALUATE the evidence APPRAISE 4. APPLY the evidence APPLY 5. EVALUATE the outcome ASSESS

20. A 63 year old male patient has a heart murmur caused by an aortic valve prolapse and is scheduled for tooth cleaning.Do you prescribe an antibiotic to be taken before dental treatment? • PICO / PECO • Population / Participants / Problem • Intervention / Exposure • Comparator / Control • Outcome

22. Appraise:Forner, JClinPerio2006 pubmed/16677328

23. Appraise: van der Meer, Arch Inter Med. 1992 pubmed/1520053

24. Appraise: van der Meer, Lancet 1992 pubmed/1346008

25. Appraise: Lockhart, Circulation 2008 pubmed/18541739

26. Appraise: Friend, USA Today The most common strain of bacteria in dental plaque can cause blood clots that induce heart attacks when they escape into the bloodstream, researchers said Monday.

27. One glossary: ebd.ada.org/GlossaryTermsCS.aspx

28. Case Report, Case Series • Characteristics: The description of interesting observations. No controls. • Purpose: to describe. Generate hypotheses. • Advantages: Simple; easy. • Disadvantages: Not conclusive. • Bias: Findings due to chance?

29. Cross-sectional Study • AKA: a survey, a poll • Characteristics: data collected on subjects at one point in time. Often looks at prevalence. • Purpose: What is happening right now? • Advantages: Short duration. • Disadvantages: Short duration. Only looks at “here and now,” not across time. • Bias: The inclusion/exclusion of subjects is critical. Representativeness: The sample is representative of what? Source: Figure 2-2, Dawson & Trapp. Basic and Clinical Biostatistics

30. Longitudinal Study Types • (usually) Retrospective Case-Control • (usually) Prospective Cohort Study • (occasionally) Retrospective Cohort Study Source: Figure 2-5, Dawson-Trapp

31. Case-Control Study • Characteristics: Begins with an outcome of interest, then look back to detect risk factors. • Purpose: to explain outcomes by evaluating previous events. What happened? • Advantage: Good for rare diseases or for those that develop over a long time period. • Quick and easy. • Disadvantage: The largest number of possible biases and errors. Strongly depends on high-quality historical records. • Bias: The major problem is the selection of the control group. Source: Figure 2-1, Dawson Trapp

32. Prospective Cohort Study • Characteristics: Follow a cohort—a group of individuals with something in common—across time. Note that some are exposed to the risk factor. • Purpose: What will happen? • Advantage: Studies the normal course of events. • Disadvantage: Takes time • Bias: Generally less subject to bias than a case-control study. Source: Figure 2-3, Dawson Trapp

33. Retrospective Cohort Study • AKA: historical cohort study • Characteristics: Attempt to follow a cohort back intime. Try to determine the risk factor. • Purpose: How did disease happen? • Advantage: Studies the normal course of events. • Disadvantage (major): depends on near perfect records. • Bias: Perhaps as biased as a case-control study. Source: Figure 2-4, Dawson Trapp

34. Experimental Studies • In vitro (eg, cellular assays) • Animal models • Humans (AKA Clinical Trials) • Note: Studies with concurrent controls are highest quality. Historic controls are problematic. • We will talk about random allocation and blind/masking next time.

35. Randomized Control Trial (RCT) • Characteristics: Specific inclusion of subjects, controlled exposure to risk factor or intervention,defined outcome measure(s) • Purpose: Does this cause that? • Advantages: Masked interventions, Blind assessment, Gold standard • Disadvantages: Difficult, expensive, time consuming • Bias: Are subjects who consent typical? • Source: Figure 2-6, Dawson-Trapp

36. Cross-over Trial • Characteristic: All subjects get both treatments Source: Figure 2-7 Dawson Trapp

37. Systematic Reviews • Narrative review • Meta-Analysis • Practice Guidelines

38. Deciding Guideline or Systematic Review Evidence-Based Guideline Systematic Review Yes No Experiment, maybe a RCT Exposure or intervention controlled by the investigator Yes No Cohort Study Subjects followed over time Yes No Case-Control Study or Case Series Subjects selected according to outcome Yes No PICOPECO Opinion,other Descriptive or Analytic PO Cross sectional / Survey

39. Study Design ≈ Level of Evidence Guideline or Systematic Review E-B Guideline E-B Guideline Systematic Review RCT Experiment, maybe a RCT Experimental trial Article Synopses ProspectiveCohort Cohort Study RetrospectiveCohort Case-Control Study Case-Control Studyor Case Series Case Series Opinion,other Narrative, Opinion Animal, In Vitro Cross sectional / Survey

40. My goals for you Be able to answer four questions: • Based on the study design, what is the level of evidence? • How were threats to validity addressed? • Based on the goals of the study, How do you describe the results? • To justify the conclusions, were comparisons done appropriately?

41. A mother asks how often her family should come in for a dental checkup for the prevention of disease.How Often? • PICO / PECO • P • IE • C • O

42. Mettes D: Insufficient evidence to support or refute the need for 6-monthly dental check-ups EBD 2005(6):62-63 • Results: “Only one study (with 188 participants) was included in this review and was assessed as having a high risk of bias. This study provided limited data for dental caries outcomes (dmfs/DMFS increment) and economic cost outcomes (reported time taken to provide examinations and treatment). • Conclusions: “There is insufficient evidence from randomised controlled trials (RCT) to draw any conclusions regarding the potential beneficial and harmful effects of altering the recall interval between dental check-ups. … pubmed/16184154

43. In-class Exercise Cross-sectional Survey ProspectiveCohort Case-Control TODAY RCT RetrospectiveCohort

44. A mother asks how often her family should come in for a dental checkup for the prevention of disease.How Often? • PICO • P children • I6-month recall • C 12-month recall • O Mean dmft/DMFT

45. Groups • 4-5 people • One reporter • Take 5 minutes

46. Case-Control Study • Selection of participants • Intervention • Measurement variables • What is measured/recorded? • When?

47. Cross-sectional Survey • Selection of participants • Intervention • Measurement variables

48. Prospective Cohort • Selection of participants • Intervention • Measurement variables

49. Randomized Control Trial • Selection of participants • Intervention • Measurement variables

50. My goals for you Be able to answer four questions: • Based on the study design, what is the level of evidence? • How were threats to validity addressed? • Based on the goals of the study, How do you describe the results? • To justify the conclusions, were comparisons done appropriately?