Course: EPIB 679-001 Clinical Epidemiology Survival analysis Date: May 9 to June 3 8:35 11:40 Session 9: Evidence-Based Medicine Dr. J. Brophy Log Rank Test Log Rank Test Log Rank Test Cox PH Model
Cox Model Cox Model Hazard Function Data Is more always better? More individual testing More facilities leading to more medical contacts Not necessarily better, be careful of lead and length time bias may give false notion of more disease and improved outcomes Theoretical construct of Law of diminishing returns
RITA -2 New York vs. Texas Stable patients randomized to medical Tx vs. PTCA PTCA less angina in the most severe patients But overall increased mortality & MI Risk adjusted outcomes in patients following MI Texans had 1.5 X angiograms After 2 years FU, had low exercise tolerance and higher mortality Mechanisms Disease thresholds Changing disease thresholds pseudodisease Low risk pts small benefits from Tx but Tx risks remain high Tampering Distraction Complexity Spectrum issues (both extremes) Competing risks Patient values Risk of Tx is often ignored Outcomes Avoiding Harm? More worry, more disability More unnecessary TX with more errors More adverse outcomes Recognize imitations of dichotomous models Ignores disease spectrum Labeling, pseudodisease, mis-specified Tx Avoid excessive extrapolation Need to be aware of the possibility
Power of stories Guidelines AAP I was finally forced to leave the wreckage due to prohibitive and deadly smoke. The first person I encountered was a mother of a 22 month old boy the same mother I had comforted and reassured right after the engine exploded. She was trying to return to the burning wreckage to find him, and I blocked her path, telling her she could not return. And when she insisted, I told her that helpers would find him. Sylvia Tsao then looked up at me and said, You told me to put my baby on the floor, and I did, and he s gone. In 2001, the AAP endorsed a proposed new requirement that children under 2 years of age ride in infant safety seats on aeroplanes, rather than being allowed to travel free on a parent s lap. BMJ 2003;327;1424-1427 The evidence Cognitive biases in perception of benefit and harm The FAA estimated that about five aeroplane crash deaths could be prevented over 10 years by adoption Because of additional cost of an aeroplane ticket for a child is likely to lead some families to drive rather than to fly, with estimated increase of about 87 road deaths Cost / death prevented was $6.4 million for each $1 cost of the ticket for the child, or $1.3 billion if the ticket cost $200. Cognitive biases in perception of benefit and harm Other paradigms than EBM Expert opinion Narrative review Power of stories
Evidence Based Medicine Why Evidence-Based Medicine? The new paradigm (religion) The High Priest The New Priests Good intentions and plausible theories are no substitute for reliable evidence from empirical research about the effects of healthcare interventions EBM - Definition Evidence based medicine: what it is and what it isn't The conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. Means integrating individual clinical expertise with the best available external clinical evidence from systematic research Is integrating the best current external evidence and individual clinical expertise Is dynamic, evolving and generally helpful Is not cookbook medicine nor a religion neither alone is enough D Sackett BMJ 1996;312:71-72 Evidence-Based Medicine Clinical (Policy) Decision Making Without clinical expertise, practice risks becoming tyrannised by evidence Evidence based medicine Evaluating the evidence Efficacy Safety Economic analysis $ / QALY Budget impact Ethics / values D Sackett BMJ 1996;312:71-72
Evidence-Based Medicine - elements Standard EBM Steps in EBM process Clinical decisions based on the best scientific evidence Best evidence means using best epidemiological and biostatistical methods (study design, analysis, interpretation) Science is meant to be cumulative as results of a particular research study cannot be interpreted with any confidence unless they have been synthesised But researchers usually don t cumulate scientifically 1. Formulate an answerable question 2. Track down the best evidence 3. Critically appraise the evidence 4. Integrate with clinical expertise and patient values 5. Monitoring your performance Its practice requires: What is the intervention? Asking Acquiring Appraising Applying Assessing If our learners are interested in the using mode, the intervention should focus on formulation of questions, searching for preappraised evidence and applying that evidence If the learners are interested in the doing mode, they should receive training in all 5 skills The intervention should match the clinical setting, available time and other circumstances What are the relevant outcomes? EBM & Patient Values Attitudes Knowledge Skills Behaviours Clinical outcomes Patient values are the beliefs that patients bring to discussions about treatment options Evidence based information is important for both clinicians and patients in making decisions about treatment options, but it is only part of the picture Patient values are a filter through which patients view the evidence that they are presented with Patients should be encouraged to express their values
Just in Time learning The EBM Approach to CME Therapy Shift focus to current patient problems ( just in time education) Relevant to YOUR practice Memorable and behaviour changed! Up to date Skills and resources for best current answers Ask a question Acquire some articles Appraise the evidence Apply the findings Assess your performance General Approach Is the study valid? Is the study valid? What are the results? Will results help me treat my patients? Proper randomization Blinded assesment of outcomes No loss to follow-up Intention to treat analysis Systematic review of all pertinent studies What are the results? Will results help me treat my patients? Is it important? How large & precise is the treatment effect? NNT for what over how long with what precision Chief emphasis on overall results (beware subgroup / post hoc analysis) Limitations of p values Confidence intervals Ideally Bayesian analysis Generalizability (comparable patients / practice patterns) Important meaningful endpoints (composite) Ask if it makes sense (synthesis with cumulative previous experience) Cost (feasibility)
Therapies P values and evidence based medicine Application Can it be applied to my patient? Can it be done here? How do patient values affect the decision? 1 RCT ===== Evidence based medicine P value <.05 The Key Information versus wisdom Avoid turning evidencebased medicine into evidence bound medicine Top successes in teaching EBM Top successes Teaching EBM succeeds: When it centers around real clinical decisions When it focuses on learners actual learning needs When it balances passive with active learning When it connects new knowledge to old When it involves everyone on the team Teaching EBM succeeds: When it matches and takes advantage of, the clinical setting, available time, and other circumstances When it balances preparedness with opportunism When it makes explicit how to make judgments, whether about the evidence itself or how to integrate evidence with other knowledge, clinical expertise and patient preferences When it builds learners lifelong learning abilities
Top 10 mistakes when teaching EBM Top 10 mistakes when teaching EBM Teaching EBM fails: When learning how to do research is emphasised over how to use it When learning how to do statistics is emphasised over how to interpret them When teaching EBM is limited to finding flaws in published research When teaching portrays EBM as substituting research evidence for, rather than adding it to clinical expertise, patient values and circumstances Teaching EBM fails: When teaching with or about evidence is disconnected from the team s learning needs about the patient s illness or their own clinical skills When teaching occurs at the speed of the teacher s speech or mouse clicks rather than the pace of the learner s understanding When the teacher strives for full educational closure by the end of each session rather than leaving plenty to think about and learn between sessions Top 10 mistakes when teaching EBM How to Practice EBM Teaching EBM fails: When it humiliates learners for not already knowing the right fact or answer When it bullies learners to decide to act based on fear of others authority or power, rather than on authoritative evidence and rational argument When the amount of teaching exceeds the available time or the learner s attention Look for seal of approval (eg Cochrane) Basic understanding of study hierarchy (RCT & meta-analyses) Awareness of potential biases Basic understanding of probability (biostatistics) Practice Decisions Lord Rayleigh 1884 Practitioners expertise Practice Decisions Preferences, values & rights.. The work which deserves, but I am afraid does not always receive, the most credit is that in which discovery and explanation go hand in hand, in which not only are new facts presented, but their relation to old ones is pointed out. Evidence from research Available resources
Principles of good practice Moving in the right direction - BMJ All new research studies should be: designed in the light of scientificallydefensible syntheses of relevant existing research evidence reported using the new evidence to update these research syntheses (thus making clear what contribution the new study has made to the total evidence) Barriers Framework for including effects of socioeconomic position in guidelines The main obstacles to applying these principles in practice are psychological and social, not practical. The practical challenge is being met by very rapid evolution and application of the science of research synthesis and electronic publishing. Aldrich, R. et al. BMJ 2003;327:1283-1285 Copyright 2003 BMJ Publishing Group Ltd. Science is cumulative, and scientists must cumulate scientifically! Question As the main funder of science, the public has a right to expect that this will be reflected more effectively in the way that science is conducted and reported. It remains unclear how effectively academia will respond to this fundamental challenge to its traditional ways of working. Can the public rely on scientists to use research synthesis to ensure that limited resources for research are used more efficiently and ethically? Needed: academic recognition that research synthesis is research and important
Question EBM Not Perfect But What About the Alternatives. If academia cannot be relied on to ensure that new research projects begin and end with syntheses of the results of other relevant studies, who will protect the public from the adverse consequences of current scientific indiscipline? BMJ 318:1999;1618 EBM The Sects Meta-anophiles Patron saint; Salim Yusuf Industrialites - Patron saint; Eric Topol Minimalists Patron saint; ISIS group and their clones