title: When to start treatment? A systematic approach to the comparison of dynamic regimes using observational data.
abstract: Dynamic treatment regimes are the type of regime most commonly used in clinical practice. For example, physicians may initiate combined antiretroviral therapy the first time an individual's recorded CD4 cell count drops below either 500 cells/mm3 or 350 cells/mm3. This paper describes an approach for using observational data to emulate randomized clinical trials that compare dynamic regimes of the form “initiate treatment within a certain time period of some time-varying covariate first crossing a particular threshold." We applied this method to data from the French Hospital database on HIV (FHDH-ANRS CO4), an observational study of HIV-infected patients, in order to compare dynamic regimes of the form "initiate treatment within m months after the recorded CD4 cell count first drops below x cells/mm3" where x takes values from 200 to 500 in increments of 10 and m takes values 0 or 3. We describe the method in the context of this example and discuss some complications that arise in emulating a randomized experiment using observational data.
authors.affiliation: Harvard School of Public Health, USA.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Cain
authors.forename: James M
authors.initials: JM
authors.lastname: Robins
authors.forename: Emilie
authors.initials: E
authors.lastname: Lanoy
authors.forename: Roger
authors.initials: R
authors.lastname: Logan
authors.forename: Dominique
authors.initials: D
authors.lastname: Costagliola
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Hernán
mesh_terms: D019380:Anti-HIV Agents / Q000008:administration & dosage*; D018791:CD4 Lymphocyte Count; D003198:Computer Simulation; D015986:Confounding Factors, Epidemiologic; D003657:Decision Making; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D015233:Models, Statistical; D012107:Research Design; D013997:Time Factors
chemical_list: D019380:Anti-HIV Agents