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• CROSSOVER DEFINITION PSYCHOLOGY TRIAL

The objective of a bioequivalence trial is to determine whether test and reference pharmaceutical formulations yield equivalent blood concentration levels. Therefore this type of design works only for those conditions that are chronic, such as asthma where there is no cure and the treatments attempt to improve quality of life.Ĭrossover designs are the designs of choice for bioequivalence trials. If treatment A cures the patient during the first period, then treatment B will not have the opportunity to demonstrate its effectiveness when the patient crosses over to treatment B in the second period. In medical clinical trials, the disease should be chronic and stable, and the treatments should not result in total cures but only alleviate the disease condition. B.Īlthough the concept of patients serving as their own controls is very appealing to biomedical investigators, crossover designs are not preferred routinely because of the problems that are inherent with this design.

A comparison is made of the subject's response on A vs. Crossover designs are popular in medicine, agriculture, manufacturing, education, and many other disciplines. Every patient receives both treatment A and B. The reason to consider a crossover design when planning a clinical trial is that it could yield a more efficient comparison of treatments than a parallel design, i.e., fewer patients might be required in the crossover design in order to attain the same level of statistical power or precision as a parallel design.(This will become more evident later in this lesson.) Intuitively, this seems reasonable because each patient serves as his/her own matched control. This is in contrast to a parallel design in which patients are randomized to a treatment and remain on that treatment throughout the duration of the trial. A crossover design is a repeated measurements design such that each experimental unit (patient) receives different treatments during the different time periods, i.e., the patients cross over from one treatment to another during the course of the trial.