Abstract #300374


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JSM 2002 Abstract #300374
Activity Number: 341
Type: Invited
Date/Time: Wednesday, August 14, 2002 : 2:00 PM to 3:50 PM
Sponsor: ENAR
Abstract - #300374
Title: Comparison of Propensity-Score-Adjusted Instrumental Variable Estimate with Intent-to-Treat Estimate in Randomized Clinical Trials with Noncompliance
Author(s): Sue Marcus*+ and Robert Gibbons
Affiliation(s): University of Pennsylvania and University of Illinois, Chicago
Address: 622 Blockley Hall, Philadelphia, Pennsylvania, 19104, USA
Keywords: intent-to-treat analysis ; clinical trials ; as-treated analysis
Abstract:

Analysis of a randomized trial is problematic when there is noncompliance with the treatment assignment. The intent-to-treat (ITT) estimates the effect of randomization rather than the effect for those who actually receive the treatment. An alternative to the ITT is the "as treated" analysis, in which subjects are classified by the treatment actually received. However, the "as treated" analysis is also flawed since confounders may be associated with switching treatment. We propose the use of an instrumental variable estimate (using the randomization as the instrument) in combination with propensity score adjustment. These methods will be illustrated with data from the Multimodal Treatment of ADHD (MTA) Study of treatment efficacy for children with attention deficit hyperactivity disorder. We show how the addition of the propensity score adjustment to the instrumental variable analysis uncovers some surprising results concerning the children who were assigned to behavioral therapy only but switched to medication.


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