|The Argument for Eveidence-Based Medicine|
Taking an evidence-based approach to practice, teaching, and research can help you address some of the limitations of current medical practice. It can help you:
Using the best evidence
Central to an evidence-based approach is the ability to ask the right question. Consider the example of patching eyes for a corneal abrasion. Identifying the best way to manage corneal abrasions begins when you ask the question "Is there any evidence that patching eyes improves outcomes for my patients with corneal abrasion." Learning how to ask these questions is a skill, and also a habit for lifelong learning.
Next, you (or a colleague) have to search all of the existing literature, to see if anyone has attempted to answer the question. Note, I said "all of the literature". An evidence-based approach requires that you systematically and exhaustively search the medical literature to identify all of the relevant evidence. Finding one or two recent and conveniently available articles that happen to support your thesis is not evidence-based medicine! Searching the literature effectively and efficiently is another skill for your EBM toolkit.
Once you have found some articles that attempt to answer your clinical question, you have to appraise their validity. Validity can be internal or external. A study with good internal validity has used the right study design and appropriate methods to answer the question. External validity can be thought of as generalizability - the results can be generalized to your patients, practice, or community. Assessing validity is an important skill, and modules 2 - 5 in this Web course will help you develop it.
Finally, you have to decide whether the results can be applied to your practice. We all operate within constraints imposed by economics, health systems, patient preferences, culture, and availability of resources. Remember, external evidence requires context.
An evidence-based approach is sometimes confused with cost-effectiveness. Not necessarily... although an evidence-based approach should increase effectiveness, it may also result in higher costs. The curve below plots increasing effectiveness against increasing cost:
Once a more effective intervention is identified, the decision to implement may depend on where it lies on the "health-policy" curve shown above. If near the lower left corner, where you get a large improvement in benefit for a small cost, it may make sense. If near the "flat of the curve", you (or your HMO, or government) may decide that the incremental benefit is not worth the additional cost. For example, a recent randomized trial demonstrated a small improvement in symptoms among patients with herpes simplex labialis who used a fairly expensive antiviral cream. While some western societies may find this benefit worth the cost, a developing country is not likely to consider this the best use of scarce resources.
EBM - improving on "common sense"
Taking an evidence-based approach gives you a solid framework for evaluating new evidence from the literature, critically appraising existing practices, and effectively using the clinical information you gather from your patients. For example, by understanding how much a test result should change the probability of disease (you will learn about this in the "Toolkit for EBM" module), you can avoid common errors of overtreatment or undertreatment. A better understanding of study designs will help you to understand the importance of randomization and systematic evaluation, rather than relying too much on anecdote and personal experience.
Reducing variation in practice
As more physicians practice in an evidence-based manner, and use the same skills and criteria to answer clinical questions, we should see less variation in practice. Evidence-based practice guidelines take into account differences between populations and allow flexibility for patient and physician decision-making. They are an efficient way to disseminate recommendations based on the best evidence without requiring each physician to do literature searches and validity assessments. However, much more research is needed on the best way to change physician practice.
Managing medical information
There are many evidence-based sources of information with "pre-digested" evidence in a user-friendly format. We will introduce you to the best of these in the "Toolkit for EBM" module. Also, in the next section (Information Mastery) we will discuss a valuable strategy for identifying the most useful new information as you "forage" to keep up with the medical literature every month.
Reversing the decline in medical knowledge
So, is there any evidence for evidence-based medicine? Sackett describes observations of McMasters University graduates (who have been trained in evidence-based medicine) and graduates of other Canadian medical schools (who were not) over a 10 year period. The McMasters graduates maintained their knowledge of the management of hypertension while the other graduates experienced a statistically significant decline. More work is needed in this area, though, and it remains an important area for future research.