Stratified medicine is based on the identification of subgroups of patients that differ in their mechanisms of disease, their susceptibility to a particular disease, or in their response to a medicine. The aim of stratified medicine is to offer the treatment that is most likely to give benefit, or to avoid an adverse reaction. Personalised medicine takes this approach a step further by using targeted medicines and also taking information such as the patient's genotype and lifestyle into account when deciding on the best treatment.