Intent-to-treat analysis in the presence of off-treatment or missing data.
Intent-to-treat (ITT) analysis is viewed as the analysis of a clinical trial that provides the least bias, but difficult issues can arise. Common analysis methods such as mixed-effects and proportional hazards models are usually labeled as ITT analysis, but in practice they can often be inconsistent with a strict interpretation of the ITT principle. In trials where effective medications are available to patients withdrawing from treatment, ITT analysis can mask important therapeutic effects of the intervention studied in the trial. Analysis of on-treatment data may be subject to bias, but can address efficacy objectives when combined with careful review of the pattern of withdrawals across treatments particularly for those patients withdrawing due to lack of efficacy and adverse events.
Keene
Oliver N
ON
GlaxoSmithKline Research and Development, Stockley Park, Middlesex, UK. oliver.n.keene@gsk.com
D015982:Bias; D002985:Clinical Protocols; D064420:Drug-Related Side Effects and Adverse Reactions; D006801:Humans; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D012107:Research Design; D013223:Statistics as Topic; D015996:Survival Rate; D016896:Treatment Outcome; D028761:Withholding Treatment