1 Seminar 6: Applied Epidemiology Chapters 8-10 Kaplan University School of Health Sciences

2 Chapter 8: Experimental Study Designs  Introduction  Hierarchy of Study Designs  Intervention Studies  Clinical Trials  Community Trials  Conclusion

3 Introduction  Experimental designs are typically implemented as intervention studies, either controlled experiments/randomized clinical trials either controlled experiments/randomized clinical trials or quasi-experiments/community trials or quasi-experiments/community trials

4 Hierarchy of Study Designs  EXHIBIT 8-1 on page 320 shows validity ranking for etiology inference according to study designs: from the highest: experimental study to the lowest: anecdote.  Randomized clinical trials are generally regarded as the most scientifically rigorous method of hypothesis testing in epidemiology.

5 Intervention Studies  Intervention studies are employed to test the efficacy of a prevention or therapeutic measure.  Controlled experimental studies involve randomization of subjects to exposure under the control of the investigator, where quasi-experimental studies involves external control of exposure without randomization.  Include Clinical trials and community trials

6 Clinical Trials  The concepts of clinical trials have a venerable history from early biblical and Greek references to increasing activity during the 18 th and 19 th centuries to present methodologic sophistication.  Some pioneering landmarks in the development of clinical trials are covered on page 331.

7 Clinical Trials  The Why, What, When, and Where of Clinical Trials in EXIHIBIT 8-2 on page 332.  Figure 8-1 on page 334 shows the steps in clinical trials: enrollment, randomization, intervention/treatment, measure of outcome.

8 Prophylactic and Therapeutic Trials  A prophylactic trial is designed to evaluate the effectiveness of a substance (such as a vaccine) or a prevention program that is used to prevent a disease.  A therapeutic trial involves the study of curative drugs or a new surgical procedure to evaluate how well they bring about an improvement in the patient’s health.

9 Prophylactic and Therapeutic Trials  One group is designated as the control arm/group to receive the standard of care, a placebo, or no intervention.  One group is the treatment arm.

10 Outcomes of Clinical Trials  Outcomes, or the results of a clinical trial, are referred to as clinical endpoints.  To access the results, investigators compare rates of disease, death, recovery, or other appropriate outcome between the treatment and control groups.  It may not be feasible to conduct randomized large long-term clinical trials. A surrogate endpoints may be used in small short-term trials (example on page 335).

11 Examples of Clinical Trials  Folic acid and neutral tube defects  Education efforts to prevent the spread of sexually transmitted diseases (STDs) Described on page

12 Blinding

13 Chapter 9: Measures of Effect

14 Chapter 10: Data Interpretation Issues