To improve your experience on Lilly TrialGuide, please use the latest version of Chrome, Firefox, Safari, or Internet Explorer, with JavaScript enabled.
This website is not optimized for your browser, as configured.
Participation

Clinical Trial Design: Parallel and Crossover Studies

WhatisaCrossoverStudy FeatureImage 29Jan2019

“Before a new drug or biologic can be marketed, its sponsor must show, through adequate and well-controlled clinical studies, that it is effective.” That directive comes from the U.S. FDA as a statement of purpose for why companies like Lilly invest in research for potential new medications. What constitutes an “adequate and well-controlled” clinical study is the subject of hundreds of pages of federal regulation, international guidelines and statistical proposals. In short, a study that is well-controlled is designed to compare two or more groups of people, with at least one of the groups taking the investigational drug (often called the study drug).

The way the groups get compared varies, depending on the study design. The most common design is called a parallel study. Participants are randomly assigned to 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. The challenge with a parallel study is that people dislike the possibility of receiving placebo, so it could be a deterrent for them to sign up to participate.

Another way of comparing groups in a research study is by using a crossover study design. This approach randomly assigns participants to one group, who then “crossover" to another treatment arm during the course of the trial. This means that even if they are initially put into a placebo group, they will also eventually receive the study drug or standard of care during the trial. Often, a washout period is used to ensure data integrity. The washout period is a predetermined amount of time during which patients receive no treatment. This period reduces carryover effects from the previous treatments and helps researchers determine whether the outcome of the study is due to the effects of the study drug.

Crossover studies typically require fewer patients than a parallel study 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.

Check out pictorial depictions of these different study designs in the infographic below. (Long-time readers of our blog may recognize the infographic from an earlier post on LillyPad.)

WhatisaCrossoverStudy Infographic 29Jan2019

Understanding clinical research can help you make an informed decision about whether to participate in a clinical trial. Beyond this short list of questions to consider, would having a better understanding of the study design help you make an informed decision? If so, what other information about study designs might be helpful? Drop us a line on Twitter to let us know!

Tags: Clinical Trial Design, Infographic,

Recent Articles

Chalkboard graphic

Chalking Up Components of Clinical Research

Leigh Anne Naas Headshot
Leigh Anne Naas
August 19th, 20192 minute read

In clinical research, who needs to know what, and when and how do they get that information? Check out our overview.

melissas-hope-featured-image

Melissa's Hope

LTGBlogAuthors GuestAuthorIcon 20July2018
Guest Author
August 5th, 20194 minute read

In part two of this two-part guest blog series, Brendan shares the experience he and his wife Melissa had as clinical trial participants.

Clinical Trial Design Across the Ages

Clinical Trial History: Clinical Trial Design Across the Ages

Leigh Anne Naas Headshot
Leigh Anne Naas
August 2nd, 20192 minute read

Clinical trials have evolved over the millennia to be more complex and more specific in the goals and outcomes they measure.

HistoryOfClinicalTrials1

Clinical Trial History: Human Protections Through the Years and Across the Globe

Leigh Anne Naas Headshot
Leigh Anne Naas
August 1st, 20193 minute read

Clinical research, by its very nature, is continually evolving through the scientific process and sometimes through human behavior.

Husband and Wife Standing on Sailboat

Love, Diagnosis and Second Opinions

LTGBlogAuthors GuestAuthorIcon 20July2018
Guest Author
June 29th, 20194 minute read

In part one of this two-part guest blog series, Brendan shares the love story of him and wife, and how unexpected symptoms resulted in a cancer diagnosis.