The Importance of Non-biological Factors in Influencing the Outcome of Clinical Trials

Abstract

The outcome of clinical drug trials is influenced both by biological and by non-biological factors. Non-biological factors can be subdivided into methodological factors and non-drug factors. The former are related to the definition and measurement of treatment course, response, and outcome itself; the latter cover characteristics of the patient, the treatment milieu, the patient's milieu apart from treatment, and (planned) psychosocial interventions. Although their mechanism of interaction with treatment outcome is not yet fully understood, these non-drug factors should be routinely monitored in clinical trials for three practical reasons: (a) to control for the heterogeneity of outcome; (b) to develop individualised outcome predictors; and (c) to promote the development of individualised guidelines for treatment indication.