title: Specifying a target trial prevents immortal time bias and other self-inflicted injuries in observational analyses.
abstract: Many analyses of observational data are attempts to emulate a target trial. The emulation of the target trial may fail when researchers deviate from simple principles that guide the design and analysis of randomized experiments. We review a framework to describe and prevent biases, including immortal time bias, that result from a failure to align start of follow-up, specification of eligibility, and treatment assignment. We review some analytic approaches to avoid these problems in comparative effectiveness or safety research.
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA; Department of Biostatistics, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA 02215, USA; Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, E25-518, Cambridge, MA 02139, USA. Electronic address: miguel_hernan@post.harvard.edu.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Hernán
authors.affiliation: Salt Lake City Veterans Affairs Medical Center, Division of Epidemiology, Department of Internal medicine, University of Utah, 500 S Foothill Blvd, Salt Lake City, UT 84149, USA.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Sauer
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Hernández-Díaz
authors.affiliation: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, 1020 Pine Avenue West, Montreal, Quebec H3A 1A2, Canada; Research Institute of the McGill University Health Centre, 1020 Pine Avenue West, Montreal, Quebec H3A 1A2, Canada; Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital, McGill University, Montreal, 3755 Côte Ste-Catherine Road, Montreal, Quebec H3T 1E2, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Platt
authors.affiliation: Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital, McGill University, Montreal, 3755 Côte Ste-Catherine Road, Montreal, Quebec H3T 1E2, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Shrier
mesh_terms: D015982:Bias; D057186:Comparative Effectiveness Research / Q000706:statistics & numerical data; D015340:Epidemiologic Research Design; D006801:Humans; D064887:Observational Studies as Topic / Q000706:statistics & numerical data*; D015983:Selection Bias; D013997:Time Factors
keywords: Comparative effectiveness research; Immortal time bias; Observational; Selection bias; Target trial; Time zero; studies