Chapter 7 Evidence-Based Medicine
A 12-year-old girl in the ambulatory clinic with fever, sore throat, red tonsils, and tender cervical adenopathy has a positive rapid test for Streptococcus. Your attending physician quizzes you about the current evidence regarding the best treatment for this patient and asks you to look up some recent articles and present the evidence at the end of the week.
INTRODUCTION TO EVIDENCE-BASED MEDICINE (EBM)
What Do I Need to Know to Use EBM?
Using EBM requires that you understand the basic principles of epidemiology and biostatistics. In addition, you should have a working knowledge of the medical literature, including common study designs, and feel comfortable performing a basic MEDLINE search. Brief reviews are in the reference list (Gehlbach, 2002; Greenhalgh, 2006).
What Does “Evidence-Based Medicine” Mean?
EBM is the “conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients” (Sackett et al., 1996). EBM assumes that physicians whose practice is based on a solid understanding of the underlying evidence will provide superior patient care. EBM guides are available for interpreting most types of articles found in the medical literature. This chapter only discusses EBM for treatment questions, because these are most commonly encountered during the clerkship. Refer to the original JAMA series (Oxman et al., 1993) or review texts (Straus et al., 2005; Greenhalgh, 2006) for additional EBM topics.
How Does EBM Use Epidemiology and Biostatistics?
EBM asks whether valid data are clinically useful for a given patient or patient population. It brings the principles of epidemiology and biostatistics into the clinical setting, looking beyond the soundness of the study design and statistical significance. EBM may demonstrate that the results of a well-designed clinical trial do not apply to your particular patient or that the results of a relatively flawed study are still quite relevant to your patient’s specific condition.
How Will I Use EBM During My Clerkship?
You will be asked often to investigate a specific clinical question in depth. EBM will help you focus the questions clearly, find relevant and quality literature, and assess its clinical usefulness. These important skills require time and practice to learn and master.
How Does EBM Relate to My Other Studies?
You will use EBM to assist with management of a specific patient or problem. The general learning during the clerkship will still come from participating directly in patient care, from reading textbooks or quality review articles, or from online resources such as the Computer-assisted Learning in Pediatrics Project (CLIPP) (http://clippcases.org).
How Do I Begin with EBM?
Before leaving the clinic or rounds, make certain that you understand the specific problem that your attending physician wants you to answer and confirm that the primary medical literature is the appropriate place to search for the answer. You should also clarify when the information is due and in what format (e.g., written or verbal presentation). Then, begin the process by focusing your questions clearly to ensure that you are addressing the specific problem and to make your literature search easier. Students commonly ask poorly formed questions, which hinders the literature search. A question such as “What is the best treatment for strep pharyngitis?” is unclear for several reasons: (1) What does “best” mean? (2) “Best” as compared to what? and (3) “Best” for whom?
How Do I Ask a Good Clinical Question?
To ensure that your question addresses the problem, consider using the PICO format: Patient, Intervention, Comparison, and Outcome. The question about appropriate treatment for streptococcal pharyngitis can be restated using the PICO format as follows: For a 12-year-old girl with streptococcal pharyngitis (Patient), is a 5-day course of penicillin (Intervention) more efficacious than a 7-day course of penicillin (Comparison) for eradicating the infection (Outcome)? Searching for the answer to this question will be easier and more rewarding than searching for the answer to the more vague question.
How Do I Use MEDLINE?
Students commonly find too many or too few articles or find articles that are not relevant. Review the basics of MEDLINE searching (Greenhalgh 1997; Greenhalgh 2006) and ask for help from a medical librarian. The following suggestions will improve your search strategy:
1 Be sure that you understand the concepts of MeSH headings and Boolean operators (“and,” “or,” and “not”).
2 Use the PICO format to focus the question and define search parameters.
3 Use the “age-limit” function appropriate to your patient.
4 Use “quality filters” to limit your search. To identify treatment articles, add “randomized controlled trial,” “clinical trial,” “meta-analysis,” and “practice guideline” to the search strategy, or use the EBM functions of Ovid and PubMed. Ask your librarian for help.
5 Read the abstracts identified by your search and choose one to three of the best articles that are relevant to your patient. Next, read each article to gain an understanding of the study’s hypothesis, methodology, and conclusions. Then, “map out” each study on paper to make the methodology and its strengths and limitations clear. This will help you determine the validity and significance of the results (Gehlbach, 2002; Greenhalgh, 2006).
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