Analysis of Missing Mechanism in IVUS Imaging Clinical Trials with Missing Covariates

• Activity Number: 344
• Type: Contributed
• Date/Time: Tuesday, August 3, 2010 : 10:30 AM to 12:20 PM
• Sponsor: Biopharmaceutical Section
• Author(s): Tianyue Zhou*+ and Ming-Xiu Hu
• Companies: sanofi-aventis and Millennium Pharmaceuticals, Inc.
• Keywords: IVUS ; Missing Mechanism ; Moving Window Method ; LOCF ; Multiple Imputation

Abstract

Intravascular ultrasound (IVUS) is an invasive medical procedure that leads to high missing rates. This paper uses an IVUS Phase II clinical trial data to explore the missing mechanism of IVUS endpoint, the percent atheroma volume (PAV). We proposed a moving window method to examine the relationship between continuous covariates such as lipid endpoint and the probability of missing IVUS values. In the example, some covariates such as lipid measures also have high missing rates after 12 months. We found that, if the method of last observation carried forward (LOCF) is used to impute the lipid endpoints, it leads to biologically unexplainable results. Using the multiple imputation approach results in a more reasonable conclusion about the IVUS missing mechanism. Age, Race, and baseline PAV are identified as key potential contributors to the probability of missing IVUS endpoint.