Chapter 5: Literature Evaluation II: Beyond the Basics

Learning Objectives

After completing this chapter, the reader will be able to

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

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

• Describe the characteristics of various observational trial designs.

• 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.

• Discuss common issues encountered in dietary supplement (botanical and nonbotanical) medical literature.

• Describe how to efficiently and effectively 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/noninferiority 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 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 quality and quantity of life affected by many different variables including disease, injury, treatment, or policy is termed health-related quality of life (HR-QOL) and is used to assist in decision making regarding interventions such as procedures and pharmacotherapy.

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 strengths 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 most reliable evidence and ...