The evidence-based approach to addressing questions concerning diagnosis, treatment, harm and prognosis begins when the clinician faces a clinical dilemma. Once the problem has been identified, the next step (and often the most difficult step) is to formulate a structured clinical question in order to search the medical literature, and then to continue on to find the best relevant evidence from that body of literature.
Three ways to use the medical literature
Consider a medical student, early in her training, seeing a patient with newly diagnosed diabetes mellitus. She will ask questions such as the following: What is type 2 diabetes mellitus? Why does this patient have polyuria? Why does this patient have numbness and pain in his legs? What treatment options are available? These questions address normal human physiology and the pathophysiology associated with a medical condition.Traditional medical textbooks that describe underlying physiology, pathology, epidemiology, and general treatment approaches provide an excellent resource for addressing these background questions. The sorts of questions that seasoned clinicians usually ask require different resources.
1. Browsing: This internist is in the process of asking a general question—what important new information should I know to optimally treat my patients? This traditional approach to what we might call the browsing mode of using the medical literature has major limitations of inefficiency and resulting frustration. Evidence-based medicine offers solutions to this problem.
2. Problem Solving: Experienced clinicians confronting a patient with diabetes mellitus will ask questions such as, In patients with new-onset type 2 diabetes mellitus, which clinical features or test results predict the development of diabetic complications? In patients with type 2 diabetes mellitus requiring drug therapy, does starting with metformin treatment yield improved diabetes control and reduce long-term complications better than other initial treatments? Here, clinicians are defining specific questions raised in caring for patients and then consulting the literature to resolve these questions.
3. Background and foreground questions: One can think of the first set of questions, those of the medical student, as background questions and of the browsing and problem-solving sets as foreground questions. In most situations, you need to understand the background thoroughly before it makes sense to address foreground issues. A seasoned clinician may occasionally require background information, which is most likely when a new condition or medical syndrome appears ("What is SARS?") or when a new diagnostic test ("How does PCR work?") or treatment modality ("What are atypical antipsychotic agents?") appears in the clinical arena.
Guyatt G, Meade MO. How to use the medical literature—and this book—to improve your patient care. Ch. 1. In: Guyatt G, Rennie D, Meade MO, Cook DJ, eds. Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. 2nd ed. New York: McGraw-Hill; 2008