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Learning Objectives

After completing this chapter, the reader will be able to

  • Describe other study designs besides the basic controlled clinical trial.

  • Discuss the potential utility, limitations, and questions to ask when evaluating other study designs.

  • Identify various observational trial designs based on differing characteristics.

  • Differentiate between the three types of literature reviews: narrative (nonsystematic) review, systematic review, and meta-analysis.

  • Describe common quality-of-life (QOL) measures used in health outcomes research and discuss the appropriate use of these measures in the medical literature.

  • Identify issues encountered in dietary supplement (botanical and non-botanical) medical literature.

  • Efficiently and effectively begin to evaluate the available evidence associated with a clinical question and categorize the quality of that evidence to develop a recommendation/clinical decision.

Key Concepts

  • 1 Although the randomized controlled trial is the most frequently used study design for clinical research, several other designs are used in specific situations, such as investigating rare outcome incidences, studying equivalency/non-inferiority between drugs, or minimizing patient exposure to new drugs with inadequate efficacy.

  • 2 Observational study designs offer an alternative to interventional trials and are used in specific situations, such as when large populations must be followed over extended periods of time. Results from these trials only allow associations to be formed rather than true cause-and-effect relationships.

  • 3 Case studies, case reports, and case series are observational or interventional reports describing patient or patient group exposure to a drug or technology and can be valuable to record preliminary findings that lead to further study. A key characteristic to these reports is the lack of a control or comparison group.

  • 4 Survey research is information gathered from an identified group with conclusions drawn and applied to a larger population. This gathered information is considered either descriptive (such as opinions and attitudes) or explanatory (such as explaining a cause and effect) in nature and the validity of the results depends on quality of the study's internal rigor.

  • 5 Meta-analyses are the only type of review providing new quantitative data derived from combining the results of each study in the meta-analysis and performing a statistical analysis on that data set. The overall reliability of a meta-analysis is ultimately dependent on the quality of the individual studies, homogeneity between these studies, and the appropriateness of the analysis.

  • 6 The value assigned to the duration of a patient's life when altered by various impairments, functional states, perceptions, and social opportunities that have been modified by disease, injury, treatment, and social policy is termed health-related quality of life (HR-QOL or HRQOL).

  • 7 The principles and criteria used to analyze the quality of drug literature are used to analyze dietary supplement (DS) literature; however, unique additional points such as standardization and purity must be considered.

  • 8 An understanding of strength and limitations inherent with each study design is essential to determine the overall quality of the evidence produced. Those trial designs with a high level of quality provide the ...

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