Critical Thinking and Evidence Based Medicine (EBM): Introduction

00:01 more highly than others, so we'll talk a little bit about how those rankings occur.

00:01 So that takes us to evidence-based medicine. Evidence-based medicine is not a new idea, but it's taken off in recent years, it has become very, very popular. It is the attempt to integrate best research evidence with clinician's personal experiences and values of their patients to make, again, meaningful evidence-based clinically appropriate choices and decisions for their patients. It's a way to use literature to help you make clinical decisions in a systematic fashion. What does systematic mean? Systematic means there's a process, there's a list, there is a step-by-step procedure to follow, by which we assess and collect the best quality evidence and summarize it in a way that answers the clinical question that we are trying to ask. So again EBM is the application of critical thinking in order to make clinical decisions. So what's best research evidence? We're trying to summarize the best research evidence to allow us to make clinical decisions, what does that mean? It's clinically relevant research, sometimes it comes from basic sciences, by which I mean lab sciences, but typically it comes from the medical literature, that is, peer-reviewed literature written by doctors or medical scientists to be consumed by other medical scientists and doctors. What's clinical expertise? That's your expertise as a clinician or a doctor or a nurse or some other kind of caregiver. So it's your ability to identify your patient's unique needs and make the evidence that you collect relevant for this particular case that you are interested in. What's patient values? Just because you find answer from literature, doesn't mean it's going to correspond to your patient's needs. For example, maybe your patient has religious beliefs that don't allow him or her to accept the finding that you have found in your research, or maybe they prefer pain alleviation or lifestyle considerations more so than lifespan elongation. These are things to consider when assessing the evidence in making your final clinical decision. But why is EBM so interesting all of a sudden? It has been around for a long time, it has been around since post-revolutionary Paris, but a couple of things, well four things in particular have caused it to gain a lot more traction in recent years. First is that doctors need daily information about how to conduct their practice, diagnosis, prognosis, therapy and prevention. That's always been the case, but now doctors are seeing more patients than ever before and are seeing a wider variety of conditions than ever before, so daily information is needed. Second, the textbook that doctors have often relied upon, are now out of date. Research is coming in so fast and so furiously and so groundbreaking, that very often the textbooks are simply not relevant anymore. There also too many journals to plow through, you haven't got a lot of time to go through them all, so what do you do? Your knowledge as a clinician is going to decline over time, this is the nature of the world, we're all getting older, we're all retaining less information in our brains and we're knowing a little bit less. We're getting wiser, but we're knowing less. You've got only a few seconds every day to deal with a mountain of evidence in between patients and you've got about 30 minutes a week that you can set aside to do additional reading to maintain your clinical expertise. Those are all some serious considerations that need a new practice, a new process, by which we can interrogate the literature to gain clinical expertise to answer clinical questions.

03:27 That takes us to evidence-based medicine. It's essentially a series of strategies for finding and appraising the best quality evidence, it's the appraising part in which the epidemiology really kicks in. How do we decide which evidence is good, which is bad? Bad is not the best word here, which evidence is good and which evidence is perhaps not as good as others.

03:49 EBM allows us to look at systematic reviews and look at summaries for ongoing research; we will define what systematic reviews are in a second, but file that term away in your memory right now. EBM also has spurred the development of evidence-based journals. These journals are now allowing us to do searches that we know are focused on good quality evidence and not just on opinion or one-off studies or things like that. It really shortens the time span between having a question and finding relevant information. We have new information systems now. I'm talking about computers, it will allow us to search very, very quickly.

04:27 Imagine doing the kinds of searches I'm going to show you in a second, 20, 30 years ago before there were computers. We had to go to libraries and search through stacks of books to find five or six articles, now we can find hundreds at the touch of a key and that's going to change everything. And lastly we have these new attitudes, new generations of doctors have new attitudes towards lifelong learning that convinces them that they need to be abreast of current information in order to be the best possible conditions.

04:56 So here are the steps of EBM or evidence-based medicine. First is that we need to convert our need for information, whatever it might be, whatever your patient demands, whatever clinical crisis is convincing you that you need to access literature, we need to convert that information into a question, not just any kind of question, but an answerable research question, and we're going to do this in a second, as an example. The second thing we need to do is we are going to have to search literature to find the best evidence to answer that question. And again, what is the best evidence? Best evidence depends upon the rankings of studies, based upon the epidemiology of those particular studies that you find. The third step in EBM is to critically appraise that evidence for its validity, impact and applicability. We are going to decide if that evidence is in fact worthy of being included in the soup of evidence that will inform the answer to your question. And lastly we're going to integrate that evidence with your particular clinical expertise. What does that mean? It means that you have wisdom, gained from a lifetime spent treating patients, or observing patients or doing research that you need to be able to bring to bear on top of all the research that you've currently conducted. This is because EBM is not simply an automated mechanical computerized system that a machine can do; it requires a human being to apply their skill sets, plus their wisdom, in order to make an appropriate clinical decision. And lastly we'd like to evaluate whether or not we’ve done a good enough job. To be honest, very few practitioners do the evaluation phase, but we encourage you to do so anyway.

06:38 So let’s go through those three conditions that I mentioned just now, validity, impact, and applicability. What does validity mean? Validity is the closeness to the truth or the real world that the study that you find purports to be. Let me think of an example for you. Let’s say you find a study that finds an association, a connection, a relationship between maternal diet and child’s intelligence, and they find that mothers who eat a lot of fat have children who grow to be very, very intelligent, but they measure intelligence via education level. In other words, the highest education that that child achieves is a proxy measurement for that child’s intelligence. Now right away, I hope you see the problem, just because you have a high education doesn’t mean you are intelligent, just because you have a low education doesn’t mean you are not intelligent. So education is an invalid measurement of intelligence. So that study would fail the validity test.

07:38 A facetious example of a valid measure is to say that a score on an IQ test is a valid measurement of one’s ability to write IQ tests. A less facetious example is to say that an ultrasound scan is a very valid test for pregnancy.

07:52 Impact is important. So you may find a relationship between two factors that's relevant for your question, but is the impact great enough to warrant you interest, and by impact I mean effect size. Did the subjects in the study change by 5%, 10%, 20%, what’s relevant to your particular condition for your patient? And lastly, applicability. You may have found a very relevant study that talks about something very similar to the question that you are asking it, but is it applicable to your case? Maybe the studies you found were down on young men and your patient is an older woman, you have to ask yourself, is that distinction? Important for your particular circumstance.