Methods and Applications of Statistics in Clinical Trials, Volume 1: Concepts, Principles, Trials, and Designs

Chapter 51

Open-Labeled Trials

Simon Day

51.1 Introduction

Open-labeled trials are a stark contrast to blinded (or masked) trials. Blinded (or masked) trials are those in which typically the patient and the treating physician (often, even if not always, synonymous with the person who observes the outcome) are unaware of the assigned treatment. Such design aspects of trials are important principally to avoid bias in selection of patients and the measurement and assessment of outcomes.

Various methods exist to help keep studies double blind. The types of methods—and their complexity—vary considerably depending on the type of trial and the type of intervention (a broader term than just “treatment”) being assessed. Other articles in this volume address such issues. The purpose of the current article is not to defend open-labeled studies but, instead, to explain why they are sometimes necessary and even sometimes preferred to blinded studies. However, even if conceptually an open-labeled study might be necessary (or preferable) to a fully blinded study, major deficiencies need to be recognized and addressed wherever possible in the study design and management.

51.2 The Importance of Blinding

In some sense, this article could be recognized as trying to defend the use of open-labeled studies, whereas other articles in this encyclopedia implicitly criticize them and strongly argue for fully blinded trials. Indeed, the importance of blinding should not be underestimated. Open-labeled trials ...