TY - JOUR
T1 - Methodology for evaluating a partially controlled longitudinal treatment using principal stratification, with application to a needle exchange program
AU - Frangakis, Constantine E.
AU - Brookmeyer, Ronald S.
AU - Varadhan, Ravi
AU - Safaeian, Mahboobeh
AU - Vlahov, David
AU - Strathdee, Steffanie A.
PY - 2004/3/1
Y1 - 2004/3/1
N2 - We consider studies for evaluating the short-term effect of a treatment of interest on a time-to-event outcome. The studies we consider are partially controlled in the following sense: (1) Subjects' exposure to the treatment of interest can vary over time, but this exposure is not directly controlled by the study; (2) subjects' follow-up time is not directly controlled by the study; and (3) the study directly controls another factor that can affect subjects' exposure to the treatment of interest as well as subjects' follow-up time. When factors (1) and (2) are both present in the study, evaluating the treatment of interest using standard methods, including instrumental variables, does not generally estimate treatment effects. We develop the methodology for estimating the effect of treatment in this setting of partially controlled studies under explicit assumptions using the framework for principal stratification for causal inference. We illustrate our methods by a study to evaluate the efficacy of the Baltimore Needle Exchange Program to reduce the risk of human immunodeficiency virus (HIV) transmission, using data on distance of the program's sites from the subjects.
AB - We consider studies for evaluating the short-term effect of a treatment of interest on a time-to-event outcome. The studies we consider are partially controlled in the following sense: (1) Subjects' exposure to the treatment of interest can vary over time, but this exposure is not directly controlled by the study; (2) subjects' follow-up time is not directly controlled by the study; and (3) the study directly controls another factor that can affect subjects' exposure to the treatment of interest as well as subjects' follow-up time. When factors (1) and (2) are both present in the study, evaluating the treatment of interest using standard methods, including instrumental variables, does not generally estimate treatment effects. We develop the methodology for estimating the effect of treatment in this setting of partially controlled studies under explicit assumptions using the framework for principal stratification for causal inference. We illustrate our methods by a study to evaluate the efficacy of the Baltimore Needle Exchange Program to reduce the risk of human immunodeficiency virus (HIV) transmission, using data on distance of the program's sites from the subjects.
KW - Causal inference
KW - HIV
KW - Needle exchange
KW - Partially controlled studies
KW - Potential outcomes
KW - Principal stratification
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U2 - 10.1198/016214504000000232
DO - 10.1198/016214504000000232
M3 - Article
AN - SCOPUS:2142787937
SN - 0162-1459
VL - 99
SP - 239
EP - 249
JO - Journal of the American Statistical Association
JF - Journal of the American Statistical Association
IS - 465
ER -