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Centre for Statistical Methodology Seminar
Friday 14 December 2018, 12:45-2:00pm
LG9, Keppel Street
Design and analysis of trials where the outcome is a rate of change, with an introduction to a new Stata package for sample size calculation
Chris Frost and Amy Mullick (LSHTM)

Abstract: A number of different approaches can be used to analyse clinical trials with a continuous outcome measured at baseline, and at several follow-up times. We first describe the general utility of linear mixed models in this setting, with a particular emphasis on trials where the aim of treatment is to slow disease progression as measured by a rate of change in the outcome. We go on to show how the statistical efficiency of, and hence required sample sizes for, such trials depends on factors such as the length of the trial and the frequency of follow-up, and describe how analysis of existing longitudinal observational data can be used to inform trial design decisions. We use data from a longitudinal study of people with Huntington’s disease to illustrate the methodology.

We also introduce a new user-friendly Stata package for sample size calculation, appropriate for planning a two-arm parallel trial of treatment that is expected to slow disease progression by a constant amount over multiple follow-up visits. The package fits a linear mixed model to a user-supplied longitudinal dataset, extracting relevant parameters to estimate mean rates of change and components of between- and within-person variability. These estimates, together with other user inputs, are then used to calculate the required sample size for a proposed trial. Users specify the visit schedule, expected loss to follow up rates, Type I and Type II error rates, and the target effectiveness of the treatment.

Centre for Statistical Methodology Seminar
Thursday 24 January 2019, 12:45-2:00pm
LG8, Keppel Street
Large numbers of explanatory variables.
Heather Battey (Imperial College London)

Centre for Statistical Methodology Seminar
Thursday 21 February 2019, 12:45-2:00pm
LG8, Keppel Street
Title TBC
Ruth Keogh (LSHTM)