Sample-Size Calculation for Count Data in Comparative Clinical Trials with Nonuniform Patient Accrual and Early Dropout

• Activity Number: 536
• Type: Contributed
• Date/Time: Wednesday, August 7, 2013 : 10:30 AM to 12:20 PM
• Sponsor: Biopharmaceutical Section
• Author(s): Huiling Li*+ and Lin Wang and Lynn Wei and Hui Quan
• Companies: Forest Research Institute and Sanofi, US and Sanofi, US and Sanofi
• Keywords: Count data ; Event rate ; Non-uniform accrual, Over-dispersion, Sample size

Abstract

In clinical trials with counts of recurrent event data, it is often of particular interest to test if the experimental treatment reduces the event rate in comparison with a control. The sample size calculation for such a trial often assumes fixed follow-up time for each patient. In many trials, however, we follow all patients for a predetermined follow-up time after the end of the accrual period, in which case the follow-up time is variable. This paper provides methods for sample size calculation for clinical trials with ordinary Poisson count data and variable follow-up time allowing for non-uniform accrual and early dropouts. We also generalize the sample size formula to count data with over-dispersion.