Getting Started: The Anatomy and Physiology of Clinical Research
Stephen B. Hulley, Thomas B. Newman, and Steven R. Cummings
This chapter introduces clinical research from two viewpoints, setting up themes that run together through the book. One theme is the anatomy of research-what it's made of. This includes the tangible elements of the study plan: the research question, design, subjects,measurements, sample size calculation, and so forth. An investigator's goal is to create these elements in a form that will make the project fast, inexpensive, and easy. The other theme is the physiology of research-how it works. Studies are useful to the extent that they yield valid inferences, first about what happened in the study sample and then about generalizing these events to peopleoutside. the study. The goal is to minimize the errors, random and systematic, that threaten conclusions based on these inferences. Separating these two themes is artificial in the same way that the anatomy of the human body does not make much sense without some understanding of its physiology. But the separation has the same advantage: It clarifies our thinking about a complex topic.
. THE ANATOMYOF RESEARCH: WHAT IT'S MADE OF
The structure of a research project is set out in its protocol, the written plan of the study. Protocols are well kn~wn as devices for seeking grant funds, but they also have a vital scientific function: helping the investigator to organize her research in a logical, focused, and efficient way. Table 1.1 outlines the components of a protocol. We will introduce thewhole set here, expand on each of them in the ensuing chapters of the book, and return to put the completed pieces together in Chapter 19. The Research Question The research question is the objective of the study, the uncertainty that the investigator wants to resolve. Research questions often begin with a general concern that must be narrowed down to a concrete, researchable issue. For example,1
TABLE 1.1 Outline of the Study Protocol
Element Research questions Significance (background) Design Time frame Epidemiologic approach Subjects Selection criteria Sampling design Variables Predictor variables Confounding variables Outcome variables Statistical issues Hypotheses Sample size Analytic approach
Purpose What questions will the study address? Why are these questionsImportant? How is the study structured?
Who are the subjects and how will they be selected? What measurements will be made?
How large is the study and how will It be analyzed?
Initial research question: Should women take hormones after menopause?
This is a good place to start, very practical and important, but the question must be focused before planning efforts can begin. Often thisinvolves breaking the whole question into its constituent parts and singling out one or two of these to build the protocol around.
More specific research questions: How commonly women take estrogen after menopause? Does taking estrogen after menopause lower the likelihood of developing coronary heart disease (CHD)? Are there other benefits and harms of estrogen treatment?
A good researchquestion should pass the "50 what?" test. Getting the answer should contribute usefully to our state of knowledge. The acronym FINER denotes five essential characteristics of a good research question: that it be feasible, interesting, novel, ethical, and relevant (Chapter 2). Significance The significance section of a protocol sets the proposed study in context and gives its rationale: What is knownabout the topic at hand? Why is the research question important? What kind of answers will the study provide? This section cites previous research that is relevant (including the investigator's own work) and indicates the problems with that research and what questions remain. It makes clear how the findings of the proposed study will help resolve these uncertainties, leading to new scientific...
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