Methodology for Evaluating a Partially Controlled Longitudinal Treatment Using Principal Stratification, With Application to a Needle Exchange Program

Constantine E Frangakis Constantine E. Frangakis is Assistant Professor and Ronald S. Brookmeyer is Professor in the Department of Biostatistics, Steffanie A. Strathdee is Associate Professor in the Department of Epidemiology, Ravi Varadhan and Mahboobeh Safaeian are doctoral students in the Departments of Biostatistics and Epidemiology, Bloomberg School of Public Health of the Johns Hopkins University, Baltimore, MD 21205. David Vlahov is Director, Center for Urban Epidemiologic Studies, New York Academy of Medicine, New York, NY. The authors thank the editor, an associate editor, three anonymous reviewers, Joshua Angrist, Phil Dawid, Donald Rubin, and Daniel Scharfstein for valuable comments. The work was completed while the . rst author was on leave at the Press Room of the President of the Hellenic Republic, and was supported in part by NIH (NEI) grant RO1 EY 014314-01.

Ronald S Brookmeyer Constantine E. Frangakis is Assistant Professor and Ronald S. Brookmeyer is Professor in the Department of Biostatistics, Steffanie A. Strathdee is Associate Professor in the Department of Epidemiology, Ravi Varadhan and Mahboobeh Safaeian are doctoral students in the Departments of Biostatistics and Epidemiology, Bloomberg School of Public Health of the Johns Hopkins University, Baltimore, MD 21205. David Vlahov is Director, Center for Urban Epidemiologic Studies, New York Academy of Medicine, New York, NY. The authors thank the editor, an associate editor, three anonymous reviewers, Joshua Angrist, Phil Dawid, Donald Rubin, and Daniel Scharfstein for valuable comments. The work was completed while the . rst author was on leave at the Press Room of the President of the Hellenic Republic, and was supported in part by NIH (NEI) grant RO1 EY 014314-01.

Ravi Varadhan Constantine E. Frangakis is Assistant Professor and Ronald S. Brookmeyer is Professor in the Department of Biostatistics, Steffanie A. Strathdee is Associate Professor in the Department of Epidemiology, Ravi Varadhan and Mahboobeh Safaeian are doctoral students in the Departments of Biostatistics and Epidemiology, Bloomberg School of Public Health of the Johns Hopkins University, Baltimore, MD 21205. David Vlahov is Director, Center for Urban Epidemiologic Studies, New York Academy of Medicine, New York, NY. The authors thank the editor, an associate editor, three anonymous reviewers, Joshua Angrist, Phil Dawid, Donald Rubin, and Daniel Scharfstein for valuable comments. The work was completed while the . rst author was on leave at the Press Room of the President of the Hellenic Republic, and was supported in part by NIH (NEI) grant RO1 EY 014314-01.

Mahboobeh Safaeian Constantine E. Frangakis is Assistant Professor and Ronald S. Brookmeyer is Professor in the Department of Biostatistics, Steffanie A. Strathdee is Associate Professor in the Department of Epidemiology, Ravi Varadhan and Mahboobeh Safaeian are doctoral students in the Departments of Biostatistics and Epidemiology, Bloomberg School of Public Health of the Johns Hopkins University, Baltimore, MD 21205. David Vlahov is Director, Center for Urban Epidemiologic Studies, New York Academy of Medicine, New York, NY. The authors thank the editor, an associate editor, three anonymous reviewers, Joshua Angrist, Phil Dawid, Donald Rubin, and Daniel Scharfstein for valuable comments. The work was completed while the . rst author was on leave at the Press Room of the President of the Hellenic Republic, and was supported in part by NIH (NEI) grant RO1 EY 014314-01.

David Vlahov Constantine E. Frangakis is Assistant Professor and Ronald S. Brookmeyer is Professor in the Department of Biostatistics, Steffanie A. Strathdee is Associate Professor in the Department of Epidemiology, Ravi Varadhan and Mahboobeh Safaeian are doctoral students in the Departments of Biostatistics and Epidemiology, Bloomberg School of Public Health of the Johns Hopkins University, Baltimore, MD 21205. David Vlahov is Director, Center for Urban Epidemiologic Studies, New York Academy of Medicine, New York, NY. The authors thank the editor, an associate editor, three anonymous reviewers, Joshua Angrist, Phil Dawid, Donald Rubin, and Daniel Scharfstein for valuable comments. The work was completed while the . rst author was on leave at the Press Room of the President of the Hellenic Republic, and was supported in part by NIH (NEI) grant RO1 EY 014314-01.

Steffanie A Strathdee Constantine E. Frangakis is Assistant Professor and Ronald S. Brookmeyer is Professor in the Department of Biostatistics, Steffanie A. Strathdee is Associate Professor in the Department of Epidemiology, Ravi Varadhan and Mahboobeh Safaeian are doctoral students in the Departments of Biostatistics and Epidemiology, Bloomberg School of Public Health of the Johns Hopkins University, Baltimore, MD 21205. David Vlahov is Director, Center for Urban Epidemiologic Studies, New York Academy of Medicine, New York, NY. The authors thank the editor, an associate editor, three anonymous reviewers, Joshua Angrist, Phil Dawid, Donald Rubin, and Daniel Scharfstein for valuable comments. The work was completed while the . rst author was on leave at the Press Room of the President of the Hellenic Republic, and was supported in part by NIH (NEI) grant RO1 EY 014314-01.

Abstract

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.

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Methodology for Evaluating a Partially Controlled Longitudinal Treatment Using Principal Stratification, With Application to a Needle Exchange Program

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Methodology for Evaluating a Partially Controlled Longitudinal Treatment Using Principal Stratification, With Application to a Needle Exchange Program

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