Purpose of review: This article provides working definitions and a conceptual framework to understand the roles of biomarkers in clinical research.
Recent findings: The definitions of the terms discussed in this article – medical signs, symptoms, biomarkers, surrogate endpoints, clinical endpoints, validation – are still under discussion, as are their relationships to each other, but broad consensus has developed in the past decade and a half about the necessity of distinguishing between, in particular, surrogate and clinical endpoints.
Summary: This article outlines the major definitions of the key terms in this field and considers select cases in which misunderstandings about the terms led to flawed research conclusions.
Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
Correspondence to Jorge A. Tavel, MD, Division of Clinical Research, National Institute of Allergy and Infectious Diseases, 6700B Rockledge Drive, Room #1127, MSC 7609, Bethesda, MD 20892, USA Tel: +1 301 402 0564; e-mail: Jtavel@niaid.nih.gov