Association of Clinical Research Professionals (ACRP) Certified Professional Practice Exam

What type of clinical trial typically requires the enrollment of the largest number of research subjects?

1. Phase I Trial

2. Therapeutic Confirmatory Trial

3. Phase II Trial

4. Observational Study

The correct answer is: Therapeutic Confirmatory Trial

The therapeutic confirmatory trial typically requires the enrollment of the largest number of research subjects because its primary purpose is to assess the effectiveness and safety of a new treatment compared to existing standard treatments or placebo. These trials are designed to provide definitive evidence on the efficacy of an intervention and often require a large sample size to detect clinically meaningful differences, control for variability, and ensure the generalizability of the results to broader patient populations. Due to the high stakes involved in confirming therapeutic benefits, a wide participant pool is essential to robustly establish the treatment's effects across diverse demographics and medical conditions. This extensive enrollment helps to enhance the statistical power of the study, allowing researchers to draw more reliable conclusions about the treatment's effectiveness. In contrast, phase I trials primarily focus on safety rather than efficacy and thus involve fewer participants, while phase II trials may enroll a moderate number of subjects to evaluate efficacy but still do not reach the scale of a therapeutic confirmatory trial. Observational studies can vary in size but typically do not focus on confirming therapeutic effects in the same way that confirmatory trials do.