Personalized, Precision, and N-of-One Medicine: A Clarification of Terminology and Concepts

"Omics technologies" now permit cost-effective molecular profiling of the human body at many phenotypic levels and over time, thus reaching far beyond the static personal genome. Such deep, dense, and dynamic analysis has exposed the uniqueness of each person with respect to health and disease in unprecedented ways, raising paradigm-disrupting questions. How valid is our medical knowledge, traditionally obtained in studies of large cohorts to produce care recommendations for a fictive "average" human, if no two people are the same? If response to treatment is different in two patients with the same diagnosis, is this because they suffer from two distinct subtypes of a disease, or because they differ in the physiology that manifests the same disease? Such questions have evoked terms, such as personalized, precision, or "N-of-one" medicine, creating potential for confusion. This article offers a terminological and conceptual delineation and presents a new approach to personal care that relies on understanding the system dynamics of an individual as opposed to relying on statistical associations. A clarification of these terms and concepts is necessary to comprehend the vision of 21st-century medicine that will harness big data to deliver "scientific wellness" for individuals.