Clinical Trials

■■❚❙❘Chapter 30Missing DataMaurille Feudjo-Tepie, Christopher Frost,Duolao Wang, and Ameet BakhaiMissing information is unfortunately common in randomizedcontrolled trials given that patients may miss visits, withdrawfrom a trial, or data may be lost. Since it is impossible to avoidmissing some data, the challenges are: (1) to design a clinicaltrial so as to limit the occurrence of missing data; (2) to controlor assess its potential impact on the trial conclusions. Targetingthe latter, in this chapter we discuss some of the problemsassociated with missing data values, for simplicity focusingon situations where the response variable is continuous. Basedon data from a hypothetical trial, we illustrate some usefulways of coping with missing data in longitudinal studies.339