Objectives

After completing this book the reader will be able to:

• Outline the overall framework of Evidence-Based Medicine
• Estimate the probability that a particular diagnosis is present
• Understand the fundamental components of decision analysis
• Estimate the treatment and testing thresholds for various medical conditions
• Understand the fundamental components of cost-effectiveness analysis
• Use a systematic approach to search MEDLINE
• Understand the key components of the Internet and how it is used to search for medical information
• Use an approach to keep up-to-date with the expanding mass of medical information
• Use a systematic approach to critically evaluate studies
• Use a systematic approach to critically evaluate integrative literature

Suggested Use for a Curriculum

This book consists of three sections in a modular format that is intended to provide a framework for the practice or study of evidence-based medicine.

The practitioner of evidence-based medicine may use the medical decision-making techniques presented in Section 1 to frame the medical problem. The first chapter, "Refining Probability," helps us make diagnoses. The next three chapters, "Decision Analysis," "Treatment & Testing Thresholds," and "Cost-Effectiveness Analysis," help us make choices with our patients. Framing the particular problem helps us identify information that we need to retrieve.

The chapters in Section 2, "Accessing Medical Information," enable us to locate the relevant information by searching MEDLINE and the Internet. After retrieving the relevant information, we evaluate it critically.

Section 3 of the book, "Assessing the Validity of Medical Information," is dedicated to developing skills of critical appraisal. A systematic five-step approach is presented in Chapter 8, "Guide for Assessing the Validity of a Study." The next chapter provides examples of the guide applied to studies of an intervention, diagnostic test, and prognosis.

Once we have retrieved and critically appraised the relevant information, we apply the information to the care of our patient, again turning to the principles described in Section 1 and Chapter 8. In this way, we use the best evidence to make diagnoses, facilitate patients' choices, and provide patients with appropriate counseling.

The book's modular format may facilitate the teaching of evidence-based medicine. Consider the structure of a month-long course for fourth-year medical students in preparation for their residency.

The first week of the course would be dedicated to learning the different medical decision-making techniques including the use of computer software such as decision analysis programs. The student would then use a particular technique to frame an important clinical scenario that they might encounter in their chosen specialty. A student entering medicine might choose to determine the treatment and testing thresholds for pulmonary embolism (as in Chapter 3). A prospective surgical intern, on the other hand, might be interested in these thresholds for appendicitis (also in Chapter 3). Alternatively, either student might be interested in using a decision analysis to determine whether they should use immunosuppressive therapy or surgery in the patient with ulcerative colitis in whom administration of corticosteroids has failed (see Chapter 2).

By the end of the first week, the student will have used a particular technique to frame the clinical problem at hand, thereby identifying the information they need to retrieve. For example, the student tackling the thresholds for pulmonary embolism will discover that it is imperative to retrieve specific information regarding the natural history of untreated pulmonary embolism, the risks and benefits of anticoagulation, and the test characteristics of the ventilation-perfusion lung scan. The second week of the course would be dedicated to learning MEDLINE and Internet search techniques to find these needles of information in the haystack of medical literature.

During the third week, students would learn the skills to evaluate medical information critically. These skills would then be applied to the systematic evaluation of the key articles they have retrieved (possibly using a journal club format).

During the final week, the students would present to their colleagues their evidence-based approach for their selected scenarios.

A Few Final Thoughts About the Context of This Book

What is the proper context of this book? To answer this, we need to consider many issues regarding evidence-based medicine. Does the practice of evidence-based medicine mean that we no longer exercise clinical judgment, rather becoming quantitative automatons? What do we do when faced with time constraints and lack of data in daily practice? Can you imagine performing a decision or threshold analysis every time you wanted to determine the best therapeutic option? You would not have time to see your patients-for that matter, you would have no free time at all!

Although many of this book's principles are presented quantitatively, the limits of data and time will more likely lead to these principles being used qualitatively. For example, use of the principles of decision analysis reminds us to at least consider the probabilities of the possible outcomes as well as the patient's preferences for those outcomes. Similarly, application of the principles of threshold analysis helps us to explicitly weigh the risks and benefits of a therapy that may better clarify whether we should have a high or low threshold for treating the patient. Furthermore, if evidence is lacking, we do not need to forestall decision-making ; the principles of evidence-based medicine highlight areas of uncertainty and provide us with an explicit framework for discussion and planning. As such, evidence-based medicine principles do not substitute for clinical judgment but rather enhance it by more explicitly highlighting the individual factors that contribute to our decision-making process.

For common clinical questions, the practitioner may feel unable to find the time to identify, retrieve, evaluate, and apply the most relevant information. However, a clinician who has invested time to develop an evidence-based approach to a commonly seen medical problem may subsequently save time by decreasing the use of unnecessary tests and treatment or the numbers of referrals made for patients.

The physician may save even more time by referring to literature that synthesizes and integrates information obtained from individual studies into a summary finding or recommendation. This type of information is known as integrative literature and comprises overviews, meta-analyses, practice guidelines, decision analyses, and cost-effectiveness analyses. In the growing mass of published studies and the increased pressure to see more patients in less time, clinicians will likely become more dependent on integrative literature to guide their practice. Clinicians will therefore need to become more facile in critically evaluating this literature. To that end, the final chapter of this book instructs the reader in how to assess the validity of integrative literature.