Abstract #300015

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JSM 2003 Abstract #300015
Activity Number: 97
Type: Contributed
Date/Time: Monday, August 4, 2003 : 8:30 AM to 10:20 AM
Sponsor: Biopharmaceutical Section
Abstract - #300015
Title: LOCF and Longitudinal Data Analyses in Clinical Trials
Author(s): Bob Zhong*+ and Jun Shao
Companies: NeoPharm, Inc. and University of Wisconsin
Address: 150 Field Dr., Lake Forest, IL, 60045-4847,
Keywords: LOCF ; ANOVA ; ANCOVA ; Nonignorable dropout ; Post-stratification ; Repeated Measures
Abstract:

In clinical trials with multiple visits, dropout often occurs. The population of patients who drop out may be different from the population of patients who complete the study. To assess treatment effects over the population of all randomized patients, we typically use the last observation carry-forward method to analyze data from the end of the trial by treating the last observation prior to dropout as the missing observation from the end of study. Regulatory agencies such as the FDA expressed their concerns about the validity of the LOCF. In this paper, we study the asymptotic validity of LOCF tests under general ANOVA and ANCOVA models. Conditions under which LOCF tests are asymptotically valid are explicitly given. We derive tests that are always asymptotically valid without using any assumptions on dropout mechanisms. Our methods post-stratify patients assigned to a treatment into subpopulations, where each subpopulation contains patients dropping out after a particular visit. Similar ideas are applied to longitudinal data analysis in clinical trials. These results can be applied to QOL data analysis, with incomparable measure-time points among treatment groups.

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