title: Methods to Estimate the Comparative Effectiveness of Clinical Strategies that Administer the Same Intervention at Different Times.
abstract: Clinical guidelines that rely on observational data due to the absence of data from randomized trials benefit when the observational data or its analysis emulates trial data or its analysis. In this paper, we review a methodology for emulating trials that compare the effects of different timing strategies, that is, strategies that vary the frequency of delivery of a medical intervention or procedure. We review trial emulation for comparing (i) single applications of the procedure at different times, (ii) fixed schedules of application, and (iii) schedules adapted to the evolving clinical characteristics of the patients. For illustration, we describe an application in which we estimate the effect of surveillance colonoscopies in patients who had an adenoma detected during the Norwegian Colorectal Cancer Prevention (NORCCAP) trial.
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA ; Institute of Health and Society, University of Oslo, Oslo, Norway.
authors.forename: Anders
authors.initials: A
authors.lastname: Huitfeldt
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA ; Institute of Health and Society, University of Oslo, Oslo, Norway ; Telemark Hospital, Skien, Norway.
authors.forename: Mette
authors.initials: M
authors.lastname: Kalager
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, Boston, MA, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Robins
authors.affiliation: Institute of Health and Society, University of Oslo, Oslo, Norway ; Telemark Hospital, Skien, Norway ; Cancer Registry of Norway, Oslo, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Hoff
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, Boston, MA, USA ; Harvard-MIT Division of Health Sciences and Technology, Boston, MA, USA.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Hernán
keywords: Causal inference; Colonoscopy; Colorectal cancer; Dynamic strategies; Inverse probability weighting; Surveillance