Chapter 001. The Practice of Medicine (Part 3)

Principles of Patient CareEvidence-Based Medicine Evidence-based medicine refers to the concept that clinical decisions are formally supported by data, preferably data that are derived from prospectively designed, randomized, controlled clinical trials. This is in sharp contrast to anecdotal experience, which may often be biased. Unless they are attuned to the importance of using larger, more objective studies for making decisions, even the most experienced physicians can be influenced by recent encounters with selected patients. Evidence-based medicine has become an increasingly important part of the routine practice of medicine and has led to the publication of a number of practice...
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Chapter 001. The Practice of Medicine (Part 3) Chapter 001. The Practice of Medicine (Part 3) Principles of Patient Care Evidence-Based Medicine Evidence-based medicine refers to the concept that clinical decisions areformally supported by data, preferably data that are derived from prospectivelydesigned, randomized, controlled clinical trials. This is in sharp contrast toanecdotal experience, which may often be biased. Unless they are attuned to theimportance of using larger, more objective studies for making decisions, even themost experienced physicians can be influenced by recent encounters with selectedpatients. Evidence-based medicine has become an increasingly important part ofthe routine practice of medicine and has led to the publication of a number ofpractice guidelines. Practice Guidelines Professional organizations and government agencies are developing formalclinical-practice guidelines to aid physicians and other caregivers in makingdiagnostic and therapeutic decisions that are evidence-based, cost-effective, andmost appropriate to a particular patient and clinical situation. As the evidence baseof medicine increases, guidelines can provide a useful framework for managingpatients with particular diagnoses or symptoms. They can protect patients—particularly those with inadequate health care benefits—from receivingsubstandard care. Guidelines can also protect conscientious caregivers frominappropriate charges of malpractice and society from the excessive costsassociated with the overuse of medical resources. There are, however, caveatsassociated with clinical practice guidelines since they tend to oversimplify thecomplexities of medicine. Furthermore, groups with differing perspectives maydevelop divergent recommendations regarding issues as basic as the need forperiodic sigmoidoscopy in middle-aged persons. Finally, guidelines do not—andcannot be expected to—account for the uniqueness of each individual and his orher illness. The physicians challenge is to integrate into clinical practice the usefulrecommendations offered by experts without accepting them blindly or beinginappropriately constrained by them. Medical Decision-Making Medical decision-making is an important responsibility of the physicianand occurs at each stage of the diagnostic and treatment process. It involves theordering of additional tests, requests for consults, and decisions regardingtreatment and prognosis. This process requires an in-depth understanding of thepathophysiology and natural history of disease. As described above, medicaldecision-making should be evidence-based so that patients derive the full benefitof the scientific knowledge available to physicians. Formulating a differentialdiagnosis requires not only a broad knowledge base but also the ability to assessthe relative probabilities of various diseases. Application of the scientific method,including hypothesis formation and data collection, is essential to the process ofaccepting or rejecting a particular diagnosis. Analysis of the differential diagnosisis an iterative process. As new information or test results are acquired, the groupof disease processes being considered can be contracted or expandedappropriately. Despite the importance of evidence-based medicine, much of medicaldecision-making relies on good clinical judgment—a process that is difficult toquantify or even to assess qualitatively. Physicians must use their knowledge andexperience as a basis for weighing known factors along with the inevitableuncertainties and the need to use sound judgment; this is particularly importantwhen a relevant evidence base is not available. Several quantitative tools may be invaluable in synthesizing the availableinformation, including diagnostic tests, Bayes theorem, and multivariate statisticalmodels. Diagnostic tests serve to reduce uncertainty about a diagnosis orprognosis in a particular individual and to help the physician decide how best tomanage that individuals condition. The battery of diagnostic tests complements the history and the physicalexamination. The accuracy of a given test is ascertained by determining itssensitivity (true positive rate) and specificity (true negative rate) as well as thepredictive value of a positive and negative result. Bayes theorem uses informationon a tests sensitivity and specificity, in conjunction with the pretest probability ofa diagnosis, to determine mathematically the posttest probability of the diagnosis. More complex clinical problems can be approached with multivariatestatistical models, which generate highly accurate information even when multiplefactors are acting individually or together to affect disease risk, progression, orresponse to treatment. Studies comparing the performance of statistical models with that of expertclinicians have documented equivalent accuracy, although the models tend to bemore consistent. Thus, multivariate statistical models may be particularly helpfulto less experienced clinicians. See Chap. 3 for a more thorough discussion ofdecision-making in clinical medicine.