An Introduction to Evidence Based Medicine

hello everyone its erik from stanford university and strong medicine today to kick off a short series on reading and applying the medical literature i'll be giving a brief introduction to evidence-based medicine or EBM for short I think when some doctors talk casually about evidence-based medicine they do so as if EBM was just about being able to quote landmark studies for example I can't count the number of times that I've been on rounds and some clinical question has come up and a physician there has said oh but as per such-and-such trial we should do this and everyone else on rounds you know nonsti head approvingly impressed by the person's recollection of some catchy study acronym like accomplish or miracle or cure and everyone there takes it for granted that the punchline that was cited applies to the patient in question and should dictate how he or she should be treated without any critical discussion of the paper or situation at all that is not practicing evidence-based medicine EBM is not remotely the same thing as memorizing the abstracts of the 50 most important trials in one's field so what is EBM EBM pioneer David Sackett from McMaster University defined EBM as this the integration of best research evidence with clinical experience and patient values in other words EBM is not just about the literature let me show you a framework for EBM and practice I'm generally not a fan of silly acronym mnemonics because they usually feel forced but this one works pretty well the five days of EBM first assess meaning identify the clinical problem next is ask which means to structure the clinical question typically using a format called Pico for a clinical trial Pico stands for patient intervention comparison and outcome so a Pico question might be for adults with advanced COPD does azithromycin compared to placebo result in fewer COPD exacerbations the next a stands for acquire the evidence then appraise meaning evaluate the evidence found last is to apply the evidence to your patient I'll be covering some of these aids in more detail in future videos in this series but to get us started with common I am terminology let's talk about the different types of studies that we might come across when acquiring the evidence we can classify clinical studies into three major categories first our observational studies in observational studies the investigators play a passive role watching patients either retrospectively or prospectively but without directly intervening observational studies can be quantitative such as cohort and case-control studies or they can be qualitative such as a case report in which a description is provided of a single patient's presentation or disease course or a case series which is a non statistical summary of multiple individual patient presentations the next broad category are clinical trials in clinical trials the investigators play an active role by administering some type of intervention to either all or some of the patients in a specific population the major type of clinical trial is the randomized controlled trial or RCT the final category of studies are reviews the standard review paper is a predominantly qualitative summary of all the knowledge and prior research about a specific disease or intervention a meta-analysis is a quantitative summary which uses standardized statistical methods to combine data from multiple individual trials which all look at identical or nearly identical questions by combining many smaller studies meta analyses can find meaningful relationships that may not have been apparent when each of the individual studies were analyzed separately due to their small sample sizes or other factors or conversely a meta-analysis of multiple conflicting studies may conclude that a particular treatment results in no meaningful benefit even if some of the included studies showed that there had been the randomized controlled trial in particular is often held up as the primary source of evidence used in evidence-based medicine and therefore I'll discuss it in more detail let's go through each word working backwards first is the most obvious one trial this means that investigator are giving some patients or study subjects and intervention controlled means that some of the study subjects receive the intervention while others don't those who don't receive either a placebo that is indistinguishable from the intervention from the patient's point of view or they receive an established conventional treatment if providing a placebo for the disease in question is felt to be unethical the non intervention group whether receiving placebo or conventional treatment is called the control group and randomized means that whether a study subject is assigned the intervention or the control is decided randomly furthermore the most well-designed RCTs are also double blinded this means that neither the study subjects nor the clinicians tasked with assessing outcomes are aware of which group an individual subject was randomly assigned to the most important advantage of RCTs over other study designs is that investigators can rigorously evaluate the effect of changing a single variable that is if the randomization of patients to the intervention and control groups is done well any difference in outcome between the two groups will presumably be due to the differences in the effectiveness of the intervention versus the control at least that's how our CTS are supposed to work in future videos I'll discuss all the ways such results and subsequent conclusions can be biased the major disadvantages of RCTs are that they are expensive they are time-consuming and they have ethical limitations on what can be tested remember in an RCT investigators are actively altering what treatments are being given to a patient which requires independent ethical oversight usually in the form of an institutional review board or IRB and in the United States also the FDA this diagram represents the hierarchy of evidence there are many different variations of it but this is one of the more common according to the conventional wisdom the most qualitative forms of evidence have a lower ranking in terms of importance while the most quantitate of are the most important bus expert opinion without supporting data rests on the bottom while a meta-analysis of multiple RCTs is at the top I'm not a fan of this hierarchy I show it because it's very commonly presented during lectures on EBM and it's beneficial to know of its existence but there are problems with it first whether intentional or not it predisposes people to consider any study in one particular level to be of superior quality and importance to any study in any level below it for example considering meta analyses to always be preferable to our CTS however that's not necessarily the case when investigators perform a meta analysis they combine data from individual RCTs and some of those RCTs are biased the meta analysis may lead to an erroneous conclusion also placing expert opinion at the bottom feels kind of unfair since expert opinion is typically forged from a career of examining evidence so even if one particular opinion doesn't have specific individual supportive studies it may still incorporate relevant knowledge from collateral evidence furthermore while personal biases certainly influence such expert opinions they absolutely can influence quantitative studies as well some people revise this hierarchy to correct for the undervaluing of expert opinion by superseding meta-analysis with clinical guidelines clinical guidelines are a collection of recommendations made by a group of experts on a particular topic after they debated the available evidence and waited against their personal experiences individual recommendations within a broader set of guidelines for the management of a specific condition are typically graded to indicate the strength of the recommendation and the quality of the supportive evidence I think placing clinical guidelines at the top is generally an improvement but it can literally take more than a decade before they are updated in order to reflect new research guidelines are also only as good as those contributing who enter the process with their own biases and sometimes a specific agenda and not every expert appraises the evidence with equal levels of skepticism this is why we can have multiple sets of clinical guidelines on the same topic which disagree in addition to the disagreement between clinical guidelines the implementation of EBM in routine practice has several other notable limitations first searching for reading and appraising the primary literature is time-consuming there is no way that a physician can apply EBM in a formal structured way to any more than a small fraction of the clinical decisions made over the course of a typical day it's tempting for a position to just read the abstracts of papers from the major journals and even to just read the conclusions in the abstracts but doing so makes way too large an assumption that the trial is valid and applicable to their patients physicians outside of major academic centers may lack access to the medical literature practicing EBM requires at least a rudimentary understanding of statistics which not all doctors acquire in medical school which may have been forgotten after years of non-use decisions about what clinical questions get studied and which studies get published are often not based on objective logical criteria for example there's a phenomenon called publication bias in which journals are more likely to publish positive clinical trials that is trials that found a benefit of an intervention over the control and researchers are dependent upon publication success for future grants and academic promotion finally many many major trials are sponsored by the pharmaceutical and medical device industries which may have millions or even billions of dollars dependent upon their results all these conflicts of interest result in an imperfect veracity of the medical literature with a bias towards new and expensive treatments rather than the boring and less profitable status quo that's not to say that there's rampant overt fraud occurring but such incentives compromise how confident we can be that the conclusions of any one study accurately reflect reality and and many times we don't even have as much as sub-optimal Studies on which to base our opinions there are countless clinical questions which have never been rigorously studied it's hard to practice evidence-based medicine in the situation which has no evidence but for many physicians the most frustrating part about EBM is a little less concrete in clinical practice our decisions are necessarily dichotomous we either operate on the patient or we don't the medication is either started or it's not and thus it would be convenient if the clinical evidence was equally dichotomous in intervention either works or it doesn't a particular study is either valid or it's not unfortunately clinical evidence is rarely if ever black or white there may be supportive evidence that a particular intervention works but not definitive proof a study may be biased but it does not necessarily mean the results are completely invalid and thus even if one knows the best available evidence practicing EBM can still be infused with a great deal of uncertainty this can make some doctors uncomfortable because they believe the scientific evidence we use in medicine should be exact precise and reproducible this is implicit in the behavior of doctors who use studies to dictate treatment decisions but without ever digging below the surface to see how methodologically sound that those studies were or how well they actually apply to the patient in question and that brings us around again to what IBM is really about it's not just the evidence it's applying the evidence together with clinical experience and patient values in order to arrived at an informed and shared decision with your patient even if the relevant evidence was perfectly quantifiable neither your clinical experience nor your patient's values are part of the beauty and joy of practicing medicine comes from the fact that it cannot be reduced down to a set of optimized algorithms instinct judgment and communication all play key roles however we still need the skills to appraise the quality of the evidence we're using even if we can't perfectly measure Anquan by its validity otherwise we'd be practicing medicine completely in the dark operating solely on faith that what we are doing is helping our patients so that's my brief introduction to EBM and some of its relevant terminology and concepts if you found it to be helpful please remember to like and share it and be on the lookout for more videos in this series to come


  1. Society is based on progress such as:
    Evidence-based constructions buildings – machinesThis exists because every part of the construction is known down to the detail, composition, size and objective.
    This allows a scientific certificate of the degree of quality to be delivered.
    Evidence-based medicine of the human body with 100% living cells that can grow, multiply and die, but nobody knows exactly how that happens.
    Consequently, delivering a scientific certificate with the grade of quality does not exist, because:- one does not know the composition of 1 living cell, let alone that medicine will determine how to repair the cells.- the totality of the number of cells is unknown.- one does not know the functions of the cells that make the body function optimally.- one does not know the totality of functions in the body.- the name, proteins, vitamins, … and their composition are a vision, but nobody can determine the exact composition of the atoms and physical properties exactly.
    The same for neurons, genes … are a name for something that is not known exactly.
    Conclusion: therefore there is no evidence-based medicine if the basic elements cannot be precisely described. The result: the human body is not a well-known medium for internal processing without causing damage.
    But the problem is much worse:- the scientists, doctors and politicians have laws approved whereby dead cells = chemicals come into contact with a medium of 100% living cells: the human body.
    The result: dead cells (chemicals) do not have a medicinal effect, but poison and a number of side effects have arisen.
    The law encourages the use of poison, this is not possible because a law cannot be used to harm people. The same reasoning applies to animals and nature that also consist of 100% living cells. The scientists are responsible for their absurd conclusions and actions.

  2. They used to be clinical guidelines to use bloodletting for most diseases. Obviously a randomised controlled trial would have delivered superior evidence

  3. Sir,
    How can I get all of your videos?
    Does you tube contains all? or you have many more?
    Can we purchase videos from All subjects?

    Thank You sir.

  4. as usual Dr Eric elucidate our long standing confusions and medical knowledge gap.
    tks a lot DOC for your commitment

  5. I would like to use this video in my EMS education for paramedics. Non commercial., Attribution will be provided. Thanks.

  6. I was taught "TIPCO" as the acronym (versus PICO)
    The "T" stands for "Time" (e.g. Treatment for 5-weeks, or 10-year survival, etc).
    – we were taught that these are the variables (in addition to a patient's informed preference) that allow you to decide if a study applies to your individual patient.
    Thanks for another great lecture!

  7. Great introduction  to EBM .  Although I was educated in Canada and  familiarized with EBM long ago , I never heard such a clear and synthetic explanation.Thank  you.

  8. Infinite thanks for this video. As a massage therapist, my education in reading high tier research is minimal. Learning how to interpret EBM will be a critical component towards my professional enrichment.
    Thank you for your videos.

  9. Outstanding, as usual. A comprehensive introduction to such a fundamental subject worldwide and one that has become specially so, here in Brazil! Looking forward to the next instalments of this series, Dr. Eric.

  10. Patient, lawyer's and hospital management always needs evidenced based treatment otherwise some day may be a bad day. Expert opinion has no say in court of law.

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