Cross-Over Trial

A Cross-Over Trial is a type of interventional clinical trial in which participants sequentially receive different treatments or a placebo. Each participant goes through all treatment options.

In such a study, participants are divided into two or more groups. Over a period of time, one group receives active treatment and the other receives placebo or standard treatment. After this, the groups switch places - the group that received active treatment switches to placebo or standard treatment, and vice versa.

The advantage of a cross-sectional study is that each participant acts as their own control. This minimizes the influence of individual differences when comparing the effectiveness of different types of therapy. The disadvantage is the “carry-over effect” - the influence of previous treatment on the subsequent one.

**Cross-over trial (XCT)** is a randomized trial used to study the effectiveness and safety of drugs or interventions in clinical trials. XCT involves studying two or more drugs at the same time (for example, the study group receives drug A and the control group receives drug B) and then rotates the groups from study to study. XCT is often used to compare the effectiveness and safety of new drugs with existing drugs.

XCT has several advantages over other types of randomized trials: * the ability to monitor the effect of adding a new drug to a patient's medication list; * more precise control over the patient’s condition during therapy: frequency of measurement of indicators, range of changes in indicators; * small sample size required for the study; * high level of therapeutic activity of study participants (patients who are under observation by one researcher throughout the study); * good suitability for remote monitoring of patients.

The main disadvantage of a crossover study compared to a double-blind study is the need to monitor all participants in the experiment. It is also important to use the crossover method only if there is an active observational group, since a non-random sample of patients may distort the result.