Crossover study

The double crossover test is an experimental method to work out factors beyond doubt with low efficacy. The double crossover test is mainly used in medicine as a design for clinical trials, but also in other areas, it is helpful to obtain statistically clean results.

Example:

• Phase 1: A patient is treated with a drug for a month.
• Phase 2: Then the medication is left out for a month or replaced by placebo.
• Phase 3: Then the drug is given one month.
• Phase 4: Then the drug is again omitted a month or replaced by placebo.

The order of the phases is often randomized. If you examine in this period conscientiously the target value, such as a medicine for high blood pressure, can also be minor effects to work out quite well. Each subject serves as its own control.

Problems of cross-over tests

The intraindividual comparison works only under certain conditions, for example under the assumption that no -over effects from one phase to the next are available. In acute events such as a heart attack or a stroke, he is useless as evidence of efficacy. The test can be applied only to stable chronic diseases.

• Evidence-Based Medicine
• Survey method ( Clinical Research)