Channeling bias in the interpretation of drug effects

Abstract

Channeling is a form of allocation bias, where drugs with similar therapeutic indications are prescribed to groups of patients with prognostic differences. Claimed advantages of a new drug may channel it to patients with special pre-existing morbidity, with the consequence that disease states can be incorrectly attributed to use of the drug. For the study of adverse drug reactions, large databases supply information on comedication and morbidity of patients. For diseases with a stepped-are approach, the drug history of patients, as available from some databases, can show channeling of drugs to patients with markers of relatively severe disease.