Outcomes Research—Preventing Infections to Improve Wound Care Outcomes: An Epidemiological Approach
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Epidemiology and Epidemiologic Research Methods
Epidemiology (from the Greek: epi = upon,demos = people) is an applied science that seeks to describe both the frequency and the determinants of disease in a population, and in doing so, leads to evidence-based prevention strategies that are implemented to reduce the incidence of disease. Much of the epidemiological evidence that drives improvements in healthcare is the product of the 3 major forms of investigation described below. An understanding of the strengths and limitations of these methods is essential when formulating new research proposals or using them to manage patients. The most fundamental of these, descriptive or observational studies, simply measure the prevalence and/or incidence of diseases or other events of interest in a population and describe the demographic characteristics of that population. Studies of this nature provide data to show what the frequency of a disease is,who is getting the disease, and when the disease is occurring. These studies are otherwise incapable of determining why some groups are more likely than others to develop a particular disease.
Analytical studies look for why diseases occur by building upon the findings of prior descriptive studies, laboratory results, clinical trials, etc., not only to characterize the frequency of disease, but also to test causal hypotheses. To do this, analytical studies collect, aggregate, and analyze data from multiple subjects with respect to their disease status and their exposure to various treatment or exposure factors that may either increase or decrease the risk of disease. Careful analysis of these data may lead to the identification of statistically significant risk or treatment factors, and to the development of interventional strategies that can be applied individually or as a part of a “bundle” to reduce the risk of disease. Finally, analysis may include methods to “risk adjust” these data in a manner that supports benchmarking and makes possible “apples to apples” comparisons between individual facilities and nationally recognized norms.
Experimental epidemiology or experimental studies actually apply identified or hypothesized interventions in a systematic way in order to measure their impact on subsequent cohorts of subjects. A clinical trial, which compares standard and new treatment modalities in 2 or more arms of a study, is a form of experimental epidemiology. Properly designed clinical trials typically yield the strongest evidence of the effects of alternative therapies, as potential confounding variables are controlled for in the subject allocation process, making it much more likely that differences in outcomes are attributable to the single variable of interest. Clinical trials are also much more difficult to initiate, because an Investigational Review Board (IRB) that provides safeguards for the study subjects must review and approve the study.
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