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

In clinical research, the term "carryover effect" is most often related to which type of design?

1. Cross-over study

2. Parallel-group study

3. Case-control study

4. Longitudinal study

The correct answer is: Cross-over study

The term "carryover effect" is most commonly associated with a cross-over study design because this type of study involves participants receiving multiple interventions sequentially. In a cross-over study, each participant serves as their own control by undergoing two or more treatments, with a washout period in between treatments to minimize any residual effects. However, if the effects of the first treatment persist into the second treatment phase, it can lead to a carryover effect, which may confound the results. This phenomenon highlights the importance of ensuring that the washout period is sufficient to allow for the complete resolution of the first intervention's effects before the next treatment begins. In contrast, a parallel-group study assigns different treatments to separate groups, which typically eliminates the risk of carryover effects since individuals are not switching between treatments. A case-control study focuses on comparing groups based on the presence or absence of an outcome without implementing treatments, thus not relevant to carryover effects. Similarly, a longitudinal study tracks the same subjects over time but does not involve switching between treatments, so carryover effects are not a consideration. Therefore, when discussing carryover effects, the cross-over study design is the most relevant and appropriately associated.