N-of-1 trial

An N-of-1 (N=1) trial is a multiple crossover clinical trial, conducted in a single patient. A trial in which random allocation is used to determine the order in which an experimental and a control intervention are given to a single patient is an N-of-1 randomized controlled trial. Some N-of-1 trials involve randomized assignment and blinding, but the order of experimental and control interventions can also be fixed by the researcher.

This type of study has enabled practitioners to achieve experimental progress without the work of designing a group comparison study. This design, especially if including blinding and wash-out periods, can be effective in confirming causality. N-of-1 trials, if used in clinical practice to inform therapeutic decisions concerned with the patient participating in the trial, can be a source of evidence about individual treatment responses, fulfilling the promise of personalized medicine.