Achieving patient-centered care and optimizing personalized treatment decisions require having information on the effects of a given treatment for a particular patient. Interindividual variability in treatments effects (known as heterogeneity of treatment effects [HTEs]) occurs when treatments that are effective for the average patient may vary in the degree of effectiveness between patients and may even be minimally effective or harmful in some patients. The n-of-1 trial is a single-patient, multiple-period crossover experiment comparing ≥2 treatments within patients. They address HTEs by providing empirical data on treatment effects for individual patients. Despite their potential to inform treatment selection, uptake of n-of-1 trials in clinical practice remains low. Previous research suggests that implementation has been hindered by a lack of understanding of use cases (eg, conditions, diseases, symptoms, and ideal circumstances) and design features that make n-of-1 trials most marketable to patients and clinicians.
