Building Clinical Evidence from Published Research

Evidence-based medicine (EBM)—asking clear, relevant clinical questions, finding appropriate studies, critically appraising the literature, and implementing changes in practice behavior—has become an essential part of medical care. Most busy physicians do not have the time or the background to answer critically the questions that arise in practice. Primary care physicians identify 2.4 clinical questions for every 10 encounters (Barrie and Ward, 1997), but they spend less than 15 minutes on average with each patient. Evidence about common primary care problems is accumulating at an overwhelming pace, and the broad scope of family medicine presents important challenges. Other barriers to the use of EBM include lack of evidence that is pertinent to an individual patient, quick access to information at the point of care, and potentially negative impacts on the art of medicine (McAllister et al., 1999). How can diligent physicians narrow the gap between their current behaviors and best practices?

In this chapter, hormone replacement therapy (HRT) for postmenopausal women is used as a case example to understand the evolution of medical practice and the changing landscape of evidence and to review concepts important to interpreting the medical literature. These concepts form the basis for practical EBM tools that family physicians can use to answer important clinical questions.

In Chapter 10, information from the Women's Health Initiative (WHI) about HRT is considered, and similar epi-demiologic and statistical issues are covered. Chapter 10 emphasizes the importance of how risk data are framed or presented to the patient and the primacy of patient preference (i.e., ability to make informed decisions about therapy) . Unfortunately, evidence concerning the ideal manner of presenting information to patients and clinicians and promoting informed decision-making is still scant. This chapter and Chapter 10 take a slightly different approach to similar clinical questions, and together, these two chapters provide the background for the motivated family physician

©2011 Elsevier Ltd, Inc, BV

DOI: 10.1016/B978-1-4377-1160-8.10008-9

Observational studies Case series descriptions ^ Case-control studies ^ Cohort studies ^

Structured reviews of observational studies

Intervention studies

Small randomized trials ^

Meta-analysis of small RCTs ^

Larger randomized controlled trials ^

Progression of studies over time

Figure 8-1 Common progression of research in building the strength of evidence; RCTs, randomized, controlled trials.

to better understand concepts of risk and probability and to foster enhanced physician-patient decision-making.

Evidence for interventions such as HRT usually begins with observational studies, including unblinded case series, case-control studies, and cohort studies, and it culminates in randomized, controlled trials (RCTs) (Figure 8-1). To better understand how we arrived at the current clinical understanding of HRT and its effects on heart disease, we review the progression of research studies and evidence over the past 30 years. A series of observational studies in the 1970s and 1980s led to regular prescribing of HRT to prevent a number of significant health conditions in postmenopausal women.

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