EVIDENCE BASED.ppt
- 2. • Periodontics is a rapidly changing field with advances in the ability to diagnose, prevent disease and slow its progression, and regenerate lost periodontium. The recent focus is on clinical decision-making and it is our duty to offer the best possible care for patients in an evidence-based manner. • Evidence-based approach (EBA) offers a bridge from science to clinical practice.
- 3. ADVANTAGES OF EVIDENCE-BASED APPROACH compared with other assessment methods (Newman et al, 2003) • Objective • Scientifically sound • Patient-focused • Incorporates clinical experience • Stresses good judgment • Is thorough and comprehensive • Uses transparent methodology
- 5. • EVIDENCE BASED MEDICINE (EBM): – Terminology introduced by EBM working group in 1992. – Evidence based health care was defined as an approach to decision-making in which the clinician uses the best evidence available, in consultation with the patient, to decide upon the option which suits the patient best. (Gray M, 1997) – Defined as the integration of the best research evidence with clinical expertise & patient values. (Sackett et al, 2000)
- 6. • Using evidence from the medical literature to answer questions, direct clinical action & guide practice was pioneered and the term EBM was coined by the clinical epidemiology group at McMaster University, Ontario, Canada, in 1980s. • However, the following aspects of EBM are new: – Methods of generating high quality evidence – Statistical tools for synthesizing & analyzing the evidence – Ways for assessing & applying the evidence
- 7. • EVIDENCE BASED DECISION MAKING (EBDM): – Defined as formalized process & structure for learning the skills for searching relevant evidence & critical appraisal so that the best scientific evidence is considered when making patient care decisions. – Fundamental principles (EBM working group, 2002): • Evidence alone is never sufficient to make a clinical decision • Hierarchies of quality & applicability of evidence exist to guide clinical decision making.
- 8. Evidence based decision making Scientific evidence Patient preferences/ values Clinical patient circumstances Experience & judgment
- 9. Need for evidence based decision making Emerged in response to the need to 1. Improve the quality of health care: driven by following forces: a. Variations in practice pattern: due to time gap between availability & application of current research knowledge b. Difficulty that clinicians confront in assimilating scientific evidence into their practices. 2. Demonstrate the best use of limited resources
- 11. Barriers to implementing evidence-based methods in dental practice (Sutherland 2000) • A lack of appropriate skills on the part of dentists in – formulating clear questions – executing efficient electronic searches – evaluating the literature • A lack of good clinical research in the form of well- designed randomized trials • Fear and mistrust by dentists regarding the use of the evidence, especially by third-party funders and regulatory authorities.
- 12. (Newman 1996)
- 13. • EVIDENCE BASED DENTISTRY: an approach to oral health care that requires the judicious integration of systematic assessments of clinically relevant scientific evidence, relating to patient’s oral & medical condition & history, with the dentist’s clinical expertise & patient’s treatment needs & preferences. (ADA, 2002) • EVIDENCE BASED PERIODONTOLOGY: an approach to patient care – Evidence-based periodontology is the application of evidence-based health care to periodontology. – It is a tool to support decision making and integrating the best evidence available with clinical practice. (Needleman et al, 2005)
- 14. How evidence-based periodontology fits into healthcare (Clarkson et al, 2003)
- 15. Development of evidence based periodontology • Evidence-based periodontology is built upon developments in clinical research design throughout the 18th, 19th and 20th centuries. • EBM: pioneered by clinical epidemiology group at McMaster University, Canada. • One of the earliest to take up the challenge in periodontology (in fact in oral health research overall) was Alexia Antczak Bouckoms in Boston, USA.
- 16. • They challenged the methods and quality of periodontal clinical research in the mid 1980s and set up an Oral Health Group as part of the Cochrane Collaboration in 1994. • The editorial base of the Oral Health group subsequently moved to Manchester University in 1997. • The first Cochrane systematic review in periodontology was published in 2001 and researched the effect of GTR for infrabony defects.
- 17. • The 1996 World Workshop in Periodontology held by the AAP included elements of evidence-based healthcare. • The 2002 European Workshop on Periodontology became the first international workshop to use rigorous systematic reviews to inform the consensus. • A similar approach was used subsequently by the AAP for the Contemporary Science Workshop in 2003.
- 18. • Many other groups are now using similar methods in healthcare and research. • The International Center for Evidence-Based Oral Health was launched in 2003 to produce high quality evidence-based research with an emphasis on, but not limited to, periodontology and implants and to provide generic training in systematic reviews and research methods.
- 19. (Clarkson et al, 2003)
- 20. EBDM process & skills (Sackett et al, 2000) 1. Converting information needs/problems into clinical questions so they can be answered 2. Conducting a computerized search with maximum efficiency for finding the best external evidence with which to answer the question 3. Critically appraising the evidence for its validity and usefulness (clinical applicability) 4. Applying the results of the appraisal, or evidence, in clinical practice 5. Evaluating the process and your performance
- 21. The steps of evidence-based Periodontology (Clarkson et al, 2003) External validity: generalizing findings Internal validity: Research methodology
- 22. 1. Asking good questions: the PICO process (Sackett et al, 2000) • A well-built question should include 4 parts that identify the – patient Problem/ Population – Intervention – Comparison – Outcomes • The format to structure the question: “ for a patient with ___ (P), will ___ (I) as compared to ___ (C) increase/ decrease/ provide better/ in doing ___ (O)?”
- 23. • Purpose of using PICO to frame the question: – Forces the clinician to focus on what he/ she & the patient believe to be the most important single issue & outcome. – Facilitates next step in process, computerized search, by identifying key terms to be used in the search. – Allows identification of the type of evidence & information required to solve the problem, as well as considerations for measuring effectiveness of intervention & application of EBDM process.
- 24. 2. Searching for & acquiring the evidence • Evidence is considered the synthesis of all valid research that answers a specific question, which distinguishes it from a single research study. (Greenhalgh, 1996) • Evidence can help inform decisions about whether a method of diagnosis/ treatment is effective relative to other methods of diagnoses/ to other treatments, & under what circumstances.
- 25. Types of Evidence based sources Primary sources: Original research publications that have not been filtered/ synthesized Secondary sources: Synthesized publications of primary literature: • SRs • Meta-analyses • EB article reviews • Clinical practice guidelines & protocols
- 26. • Searching the evidence – Use biomedical database: • MEDLINE (Pubmed, strong on English- language studies) • EMBASE (strong on other European languages), • HealthSTAR • CINALH (cumulative index to nursing & allied health ) • CENTRAL (the Cochrane Collaboration register of trials records)/ Cochrane collaboration library (Database of SRs)
- 27. – Electronic journals – Evidence based journals: provide concise & easy to read summaries of original research articles & SRs selected from biomedical literature: 1.Journal of evidence based dental practice 2.Evidence based dentistry • PICO question provides the foundation for search terms.
- 28. Hierarchy & Levels of clinical evidence Meta-analysis, systematic reviews RCTs Cohort studies Case control studies Case reports Ideas, editorials, opinions Animal research In vitro (test tube) research Relevance to answering clinical questions Amount of available literature
- 32. • This hierarchy of evidence is based on the concept of causation & need to control bias. • Systematic Reviews & meta-analyses using 2/> RCTs of human subjects are considered the gold standard for evidence because of their strict protocols to reduce bias. • A systematic review (SR) can be defined as a review of a clearly formulated question that attempts to minimize bias using systematic and explicit methods to identify, select, critically appraise & summarize relevant research.
- 35. Purposes of systematic review • Reduces a large amount of information to a manageable size. • Determines the consistency & generalization of results. Also offers the opportunity to explain any inconsistencies. • Usually cheaper and quicker to conduct than to embark on a new study. • May reduce the delay between research discoveries and the implementation of new effective treatment strategies.
- 36. • Combines information from individual studies so results in an increase in the power of the investigation & the precision in obtaining estimates of the effects of interest. Thus, the SR has a greater chance of eliciting significant treatment effects, which is particularly helpful if the prevalence of the condition is low or if the effect of interest is small. • Limits bias and improves the reliability and accuracy of recommendations because of its formalized and thorough method of investigation.
- 38. • Meta-analysis: – A special form of systematic review (sometimes called an overview) – A statistical approach to combining the results from separate but similar studies to provide an overall quantitative summary of the effect of interest. Thus, increasing the sample size, power & the precision of estimates of treatment effects & exposure risks. – In practice, the meta-analysis is open to criticism, essentially on four grounds (Glass et al., 1981): 1.Publication bias: Because journals rarely publish a negative trial in which a clinically significant effect is essentially ruled out.
- 39. 2. Clinical heterogeneity in features of studies (design, outcome measure, measuring technique, definition of variables & subjects, duration of follow-up). 3. Quality of studies (mostly only high quality studies) included. Instead both ‘good’ and ‘bad’ studies should be included & handled empirically by conducting separate analyses for groups of studies of similar quality & examining whether the results differ for poorly and well designed studies. 4. The results included in the meta-analysis may not be independent.
- 40. • This “ladder of evidence” was developed to a large extent for questions related to interventions or therapy. For questions related to diagnosis, prognosis or causation, other study designs such as cohort studies or case control studies will often be more appropriate. For these types of studies, it is useful to think of the various study designs not as a hierarchy, but as categories of evidence, where the strongest design which is possible, practical & ethical should be used.
- 42. • Clinical practice guidelines & protocols: – Guidelines are systematically developed statements to assist practitioner & patient decisions about appropriate health care for specific clinical circumstances. (National Academy of sciences, 2000) – Should incorporate the best available scientific evidence. – Includes: • ADA guidelines • AHA guidelines – AAP position papers, statements & parameters of care, although not identified as guidelines, have been developed & updated on multiple aspects of periodontal practice.
- 43. 3. Appraising the evidence • Critical Appraisal: The process of assessing & interpreting evidence by systematically considering its validity, results & relevance to your own work. • Critical analysis guides: – CASP (critical appraisal skills program): to review RCTs, SRs & several other types of studies. – CONSORT (Consolidated Standards of Reporting Trials) for RCTs
- 44. – STARD (Standards for Reporting of Diagnostic Accuracy) for reporting studies on diagnostic tests. – Guidelines for reporting SRs: • QUOROM (Quality of Reporting of Meta- analyses) • MOOSE (Meta-analysis Of Observational Studies in Epidemiology) • QUADAS (Quality Assessment of studies of Diagnostic Accuracy included in SRs)
- 45. • Common ways used to report results (Sackett & colleagues, 2000): measures to be reported in determining the magnitude of therapy results: 1. Event Rate: The proportion of patients in a group in whom the event is observed. Control Event Rate (CER) & Experimental Event Rate (EER) are used to refer to this in control and experimental groups of patients respectively. 2. Absolute Risk Reduction (ARR): The difference in event rate between the control group (CER) & the experimental group (EER).
- 46. Relative Risk Reduction (RRR): The percent reduction in events in the treated group event rate (EER) compared to the control group event rate (CER 3. Numbers needed to treat (NNT): the number of patients (surfaces, periodontal pockets) that would need to be treated with the experimental treatment or intervention to achieve one additional patient (surfaces, periodontal pockets) who has a favorable response.
- 47. Tools for assessing evidence 1. Be skeptical: a. Large number of effective periodontal treatments may be telltale sign of a challenging chronic disease. b. Complex nature of periodontal disease with both genetic & environmental causes, makes the diagnosis, treatment & investigation challenging. c. Scientific quality of periodontal studies have been rated as low. (Antczak)
- 48. 2. Don’t trust biologic plausibility a. Decisions based on “causal chain thinking, sometimes referred to as deductive inference/ deductive reasoning/ logical system” are not universal, thus classified as level 5 in EB medicine. causes causes A B C
- 49. b. Much of our knowledge on prevention & management of chronic periodontitis depends largely on deductive reasoning: i. Short term changes in PD/ AL have been assumed to translate into tangible, long term patient benefits. ii. Evidence that plaque control affects the most forms of periodontal diseases is still weak. iii. Use of antibiotics for painful periodontal abscess is rationalized on deductive inference.
- 50. 3. What level of controlled evidence is available? • Inductive reasoning: rational thoughts based on systematic experiments • Systematic experiments routine in clinical research: i. RCT: gold standard design in clinical research ii. Cohort study iii. Case-control study
- 51. • An important challenge in assessment of controlled evidence is determining whether the association between exposure & endpoint is causal using following factors: i. Temporality ii. Presence of pretrial hypothesis iii. Size/ strength of reported association • Conclusions based on controlled study designs are always surrounded with a degree of uncertainty.
- 52. 4. Did the cause precede the effect? • Unequivocal establishment of temporality is an essential element of causality, i.e, cause needs to precede the effect & can be difficult to establish for chronic diseases, including epidemiology of periodontal diseases. • Many studies in periodontal research suffer from unclear temporality: a. Studies relating to plaque/ specific infections to periodontal disease. b. Observed microbial profiles: result/ cause of periodontitis? c. Potential association between chronic periodontitis & systemic diseases.
- 53. 5. Prediction Essential characteristic of scientific enterprise: prediction: hypothesis/ ideas predict observations, they can not be fitted into observed data. a. A common post trial modification of hypothesis is to evaluate proper/ improper subgroups of original study sample. – Improper subgroups are based on patient characteristics that may have been influenced by the exposure. Results of such analyses are almost always meaningless when establishing causality. – Proper subgroups are based on patient characteristics that cannot be influenced by the exposure. E.g.., age, gender, race. Even these results may turn out to be misleading in majority of cases.
- 54. b. After/ during the conduct of study, the exposure definition can be changed/ the no. of exposures under the study can be modified. The results of such studies can not be duplicated. c. In periodontal research the absence of a specific pre-trial defined primary endpoint permits effortless changing of the endpoint definition. • Data torturing: deviating from pretrial hypothesis (Mills, 1993) – Opportunistic data torturing: exploring data without the goal of proving a particular point of view. It is an essential aspect of scientific activity & hypothesis generation. – Procrustean data torturing: exploring data without the goal of proving a particular point of view.
- 55. 6. What is clinically relevant pretrial hypothesis? Characteristics of pretrial hypothesis: a. Clinically relevant endpoint (outcome in PICO) – Endpoint: measurement related to a disease process/ condition & used to assess the exposure effect. • True endpoint: tangible outcomes that directly measure how a pt. feels, functions/ survives. Pretrial specification of true endpoint is the first requirement for a clinically relevant study. • Surrogate endpoint: intangible outcomes used as a substitute for true endpoint. Treatment effects on surrogates do not necessarily translate into real clinical benefit.
- 56. a. Relevant exposure comparisons (intervention & control in PICO): providing the control subjects with less than standard dose of treatment is example of clinically irrelevant research. b. Study sample representative of real world clinical patients (patient in PICO) c. Small error rates:to minimize false positive & negative conclusions. – Type I error rate: likelihood of concluding there is an effect, when in truth there is no effect. It is set by the investigator at 1% or 5%. – Type II error rate: likelihood of concluding there is no effect, when in truth there is an effect. It is set by the investigator at 10% or 20%. Complement of type II error rate (1- type II error rate) is referred to as power of the study.
- 57. 7. Size of association • The larger the association, the less likely it is caused by bias, & the more likely it is causal. • A simple way to calculate the size of association is to calculate the odds ratio. • The Odds for an event is the probability that an event happens divided by the probability that an event does not happen. • Odds Ratio: ratio of odds. Ranges between zero & infinity: – OR=1: absence of association – OR>1: harmful effect – OR<1: protective effect
- 58. • Confidence interval: range of numbers between the upper & lower confidence limits. – Contains true OR with a certain predetermined probability (e.g. 95%) 8. Methodological errors • Confounding is a term that describes the situation where an estimate of the association between an exposure and the disease is mixed up with the real effect of another exposure on the same disease, the two exposures being correlated.
- 59. Criteria for a variable to induce association Confounding Variable Endpoint Exposure Causal association Association present? (not necessarily causal) Investigated Causal association
- 60. • Confounding can be dealt with at the design stage of an investigation by: a. Randomization: usually the most effective way of minimizing the problem of confounding. b. Restriction: participation of specific groups which are similar to each other with respect to the confounder c. Matching: comparison groups with similar backgrounds • Confounding can also be controlled for in the analysis by: a. Stratification: strength of the association is measured separately in each well-defined subgroup & the results are pooled together using basic statistical techniques to obtain an overall summary measure of the association adjusted or controlled for the effects of the confounder.
- 61. b. Statistical modeling – mathematical techniques that can simultaneously take into consideration the effects of several possible confounders recorded by the investigators. • In epidemiologic studies with no randomization, following points need to be considered in the assessment of causality: a. Identification of all confounders: • Crude association: association unadjusted for any potential confounders • Adjusted association: crude association adjusted for potential confounders
- 62. b. Accuracy of measurement of confounders: • A discrepancy between measured & true value of confounder will result in incomplete removal of bias, leading to spurious associations. • The remaining bias is referred to as residual confounding, one of the reasons on less effectiveness of case-control & cohort studies compared to randomized trials in identifying small effects. c. Appropriateness of statistical model: any misspecification of functional relationship cause bias.
- 63. Bias • A systematic error that leads to results which are consistently wrong in one or another direction. • The main types of bias: 1. Selection bias: how subjects were selected for inclusion in a study. It is a major concern in the design of case-control studies. It is essential to ensure that controls are representative of the population from which the cases originated and randomization is properly achieved. 2. Performance bias: provision of care. Blinding is essential to rule out this bias.
- 64. 3. Detection/measurement bias: assessment of outcomes, may be introduced by a. the observer (observer bias), b. by the study individual (responder bias) c. by the instruments (instrument bias) used to make the measurements 4. Attrition bias: occurrence and handling of patient attrition (withdrawal from the study before its completion)
- 65. 5. Publication bias: the greater likelihood of publication of studies with positive results than those with neutral or negative results. As a result, interventions appear to perform better than they will in clinical practice. Graphic & formal statistical tests are available to investigate publication bias but need approximately 10 or more studies to have adequate power. • Chance: sampling error: plays a role in most studies of humans since it is rarely if ever possible to include an entire population in an investigation, therefore, studies attempt to infer information about the population on the basis of that obtained from representative samples drawn from that population & the extent of inference is assessed by statistical significance tests & confidence intervals.