title: Correcting for non-compliance in randomized trials: an application to the ATBC Study.
abstract: Different methods for estimating the effect of treatment actually received in a longitudinal placebo-controlled trial with non-compliance are discussed. Total mortality from the ATBC Study is used as an illustrative example. In the ATBC Study some 25 per cent of the participants dropped out from active follow-up prior to the scheduled end of the study. The 'intention-to-treat' analysis showed an increased death risk in the beta-carotene arm when compared with the no beta-carotene arm. Owing to considerable non-compliance it is also of interest to estimate the effect of beta-carotene actually received. We use a simple model for the treatment action and discuss three methods for estimation of the treatment effect under the model - the 'intention-to-treat' approach, the 'as-treated' approach and the g-estimation approach. These approaches are compared in a simulation study under different settings for non-compliance. Finally, the data from the ATBC Study are analysed using the proposed methods.
authors.affiliation: Rolf Nevanlinna Institute, P.O. Box 4, FIN-00014, Helsinki, Finland. Pasi.Korhonen@RNI.Helsinki.fi
authors.forename: P A
authors.initials: PA
authors.lastname: Korhonen
authors.forename: N M
authors.initials: NM
authors.lastname: Laird
authors.forename: J
authors.initials: J
authors.lastname: Palmgren
mesh_terms: D003198:Computer Simulation; D005387:Finland; D006801:Humans; D008175:Lung Neoplasms / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D016016:Proportional Hazards Models; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D012907:Smoking; D016312:Treatment Refusal / Q000706:statistics & numerical data*; D014810:Vitamin E / Q000627:therapeutic use; D019207:beta Carotene / Q000627:therapeutic use
chemical_list: D019207:beta Carotene; D014810:Vitamin E