The compliance score as a regressor in randomized trials

• Published in: Biostatistics (Oxford, England) Vol. 4; no. 3; pp. 327 - 340
• Main Authors: Joffe, Marshall M, Ten Have, Thomas R, Brensinger, Colleen
• Format: Journal Article
• Language: English
• Published: England Oxford Publishing Limited (England) 01-07-2003
• Subjects: Bias; Causality; Cholesterol - blood; Cholestyramine Resin - therapeutic use; Humans; Patient Compliance; Randomized Controlled Trials as Topic - methods; Randomized Controlled Trials as Topic - standards; Statistics as Topic - methods; Treatment Outcome
• ISSN: 1465-4644; 1468-4357
• DOI: 10.1093/biostatistics/4.3.327

The compliance score in randomized trials is a measure of the effect of randomization on treatment received. It is in principle a group-level pretreatment variable and so can be used where individual-level measures of treatment received can produce misleading inferences. The interpretation of models with the compliance score as a regressor of interest depends on the link function. Using the identity link can lead to valid inference about the effects of treatment received even in the presence of nonrandom noncompliance; such inference is more problematic for nonlinear links. We illustrate these points with data from two randomized trials.