Infographic: What Is A Crossover Study? Reply

The randomized controlled trial (RCT) is commonly referred to as the gold standard in clinical research. From Wikipedia:

The key distinguishing feature of the usual RCT is that study subjects, after assessment of eligibility and recruitment, but before the intervention to be studied begins, are randomly allocated to receive one or other of the alternative treatments under study.

Still, there are various ways a clinical trial can be designed to both achieve the objectives of the patients and researchers and to test that a new treatment is safe and efficacious. As you scroll through trials on ClinicalTrials.gov, you may notice references to Adaptive study designs, Balanced and Unbalanced study designBio-Availability and Bio-Equivalence studies, and many more. Understanding more about the terminology and methods used in a clinical trial might help patients to more easily determine whether a clinical trial is right for them.

We’ve chosen to focus on crossover studies for our latest infographic. Crossover studies can be of special interest to some patients, because they typically ensure that every participant will receive the study drug at some point during the trial.

Patient Paths on Parallel and Crossover Studies

For the more common parallel study, patients who enroll are randomly assigned into one of two or more treatment arms. Each treatment arm could include a particular dose of the study drug, a placebo or a standard of care treatment. Patients then remain in that same treatment arm throughout the course of the study.

Rather than participants remaining on on a single treatment path (the study drug, a placebo, or standard of care) in a parallel trial, patients in a crossover study will “crossover” to another treatment arm during course of the trial. This means that even if they are initially put into a placebo arm, they will also eventually receive the study drug or standard of care during the trial. Data integrity is ensured by instituting a washout period—a gap in between arms where patients don’t receive any medication—in order to reduce carryover effects from the previous treatments.

What are some impacts of Crossover design?

Crossover studies typically require fewer patients than a parallel trial since each patient acts as his or her own control, meaning that they receive both the study drug as well as the placebo or standard of care treatment. However, crossover studies can take longer to complete since patients will receive multiple treatments during the trial.

Do you think that knowing more about study terminology and designs helps you feel better prepared to make a decision about participating in a clinical trial? What could sponsors and researchers do to help patients learn more about study designs? Tell us in the comments below…

crossover study, parallel study, clinical trials

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