Certified Clinical Research Associate (CCRA) Practice Exam 2026 – All-in-One Guide to Master Your Certification!

Crossover study designs involve participants receiving multiple treatments in a sequential manner, which allows individual participants to serve as their own controls. One of the significant challenges associated with this design is the presence of carryover effects.

Carryover effects occur when the effects of the first treatment persist and influence the response to the second treatment. This can confound the results, as it becomes difficult to distinguish whether any observed effects are due to the second treatment or residual effects from the first. This issue is particularly relevant in situations where the treatments have long-lasting effects or if the time between crossover is not sufficient for the first treatment to wash out fully.

The other options, while potential challenges in clinical trials, are not unique to crossover designs. For instance, crossover bias is a term that could refer to biases introduced in crossover studies, but it is not the most significant challenge compared to carryover effects. Patient dropouts can occur in any study design and are not exclusive to crossover studies. Informed consent issues can arise in any clinical trial scenario, making them less specific to crossover designs as well. Therefore, carryover effects stand out as the major challenge in crossover study designs.