Methods and Applications of Statistics in Clinical Trials, Volume 2: Planning, Analysis, and Inferential Methods

Chapter 3

Assessment of Health-Related Quality of Life

C. S. Wayne Weng

3.1 Introduction

Randomized clinical trials are the gold standard for evaluating new therapies. The primary focus of clinical trials has traditionally been evaluation of efficacy and safety. As clinical trials evolved from traditional efficacy and safety assessment of new therapies, clinicians were interested in an overall evaluation of the clinical impact of these new therapies on patient daily functioning and well-being as measured by health-related quality of life (HRQOL). As a result, HRQOL assessments in clinical trials rose steadily throughout the 1990s and continue into the twenty-first century.

What is HRQOL? Generally, quality of life encompasses four major domains [1]:

1. Physical status and functional abilities

2. Psychological status and well-being

3. Social interactions

4. Economic or vocational status and factors

The World Health Organization (WHO) defines “health” [2] as a “state of complete physical, mental, and social well-being and not merely the absence of infirmity and disease.” HRQOL focuses on parts of quality of life that are related to an individual’s health. The key components of this definition of HRQOL include (1) physical functioning, (2) mental functioning, and (3) social well-being, and a well-balanced HRQOL instrument should include these three key components. For example, the Medical Outcomes Study Short Form-36 (SF-36), a widely used HRQOL instrument, includes a profile of ...