Chapter 4: Drug Literature Evaluation I: Controlled Clinical Trial Evaluation

Learning Objectives

After completing this chapter, the reader will be able to

• List and explain the skills pharmacists need to locate and evaluate current information for pharmacy practice activities.

• Describe special characteristics of a controlled clinical trial that distinguish this research design as the prototype for clinical research.

• Prepare a null hypothesis (H₀) based on the clinical trial objective(s) and endpoint(s).

• Differentiate between the types of data and measures of central tendency.

• Differentiate between Type I and Type II errors; discuss methods to reduce the possibility of either of these errors occurring.

• Interpret p-values and 95% confidence intervals (CI); discuss whether to reject or fail-to-reject H₀ by using these clinical trial results.

• Calculate and interpret relative risk (RR), relative risk reduction (RRR), absolute risk reduction (ARR), and number needed to treat (NNT).

• State whether a statistical significance and clinical difference are present using the clinical trial results.

• Explain the purpose and usage of editorials, letters to the editor, and secondary journals in critiquing clinical trials and in the decision-making process of applying the results to practice.

Key Concepts

1. Pharmacists need to efficiently locate, critically analyze, and effectively communicate data from the primary literature in daily activities of patient care and the medication use process.

2. A controlled clinical trial is the premier study design to measure and quantify differences in effect between the intervention and control.

3. Decision making should not rely solely on reading abstracts; the entire manuscript is to be read and thoroughly evaluated.

4. The results of a controlled clinical trial should be extrapolated to the type of patient enrolled in the study, and readers should be aware of the limitations of surrogate endpoints and subgroup analysis results.

5. Randomization is an essential component of controlled clinical trials and a significant differentiator from other study designs.

6. The controlled clinical trial primary endpoint should be appropriate for the study purpose and measured using valid techniques and methods.

7. An appropriate sample size in a controlled clinical trial is vital for the study results to have any significant meaning; conducting a power analysis is important to determine a suitable sample size.

8. Interpreting the p-values correctly is crucial in evaluating a controlled clinical trial; not all statistically significant p-values are clinically important. The magnitude of difference in effect between the intervention and control cannot be determined solely with the p-value.

9. The use of 95% CI can assist the reader in assessing the magnitude of difference in effect between the intervention and control to apply to the population.

10. Calculating measures of association (relative risk, absolute risk reduction, relative risk reduction, number needed to treat) for nominal data provides further information to evaluate the meaning of controlled clinical trial results.

11. Nonstatistically significant results do not equate to the intervention and control being the same or equal.

12. All controlled clinical trial results need to be assessed to determine the clinical relevance (i.e., meaningfulness) of the intervention ...