Guyatt G, Rennie D. Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. Chicago: American Medical Association, 2001.

Since its introduction in JAMA in 1993, the article series has become the standard for understanding and using the medical literature in daily practice. This series of 25 articles clarifies the principles of evidence-based medicine, and provides clear and practical guides for accessing and evaluating articles published in the medical literature. Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice is not only a compilation of the users' guides from the JAMA series; it also modifies, expands, and updates the original articles.

Rennie's insightful analogy in the foreword of the book states that the medical literature is “clearly visible but utterly inaccessible”, a message that serves as an honest appraisal of the difficulties faced by clinicians who are attempting to go beyond “experience-based medicine”. Exponential growth in the volume of medical literature complicates efforts to translate new research findings into care for individual patients. Fortunately, this book provides lucid directions for a method of meeting this challenge. It is written for “any clinician who wishes to understand the medical literature, and to use it more effectively in solving patient problems”, that is, any clinician caring for patients.

The book is divided into 2 sections: part 1, “The Basics”, presents the core principles of evidence-based medicine as well as a systematic approach to searching, understanding, and using the medical literature, including articles about treatment, diagnosis, harm, differential diagnosis, and prognosis; part 2, “Beyond the Basics”, provides more in-depth explanations of statistical methods and teaching tools. Critics of evidence-based medicine often argue that it is just numbers and statistics and that it ignores individual clinicians' experience and patient values. Part 1 begins by disputing this claim, with examples that show how clinical judgment and decision making are paramount to the practice of evidence-based medicine. Subsequent topics include formulating focused, clinical questions; determining the best possible study design to answer these questions; and using suitable databases to find answers. Examples of searches with such databases as Medline, the Cochrane Library, Best Evidence, and UpToDate are included. The emphasis on “prefiltered” evidence is essential for practicing clinicians because they usually lack the time or training to conduct critical appraisal of primary medical literature.

In part 1, the reader is introduced to critical appraisal in a way similar to that presented in the users' guides in the JAMA series: learning to evaluate a study's validity, understanding the results, and determining its applicability to a given patient. Clear descriptions and examples of this systematic approach to the literature are given, providing an understanding of the concepts necessary to become a competent evidence-based practitioner.

For further information on the topics discussed in part 1, links are given to those portions in part 2 that delve more deeply into these areas. For example, in part 1, a study on a therapeutic intervention is examined in terms of validity issues, but understanding the study results is not explored. Part 2 provides more detailed explanations of absolute and relative risk, number needed to treat, confidence intervals, and p values. Issues related to the application of the results, such as individual patient differences, quality of life, surrogate outcomes, and drug class effects, are also addressed in the second part of the book.

One remarkable aspect of this publication is that it transcends the static nature of a book. Usually, once published, no changes to a book are possible until the next edition has been prepared (often many years away). However, in addition to the print version, a website will soon be available to provide updates and interactive learning modules. A CD accompanies the book, allowing installation of an interactive version on one's own computer. Clicking on icons takes the user to the internet and allows quick access to citations, if they exist, in PubMed.

Because we both have personally experienced Guyatt's brilliant evidence-based medicine teaching, we are delighted to have this resource to aid us in teaching medical students, residents, and faculty. We wish that this book, instead of a biochemistry textbook, was required reading for medical students. We hope that all clinicians will not only read but also study this reference, because we believe that patients would certainly benefit.