Health-related quality of life--an introduction.

Chronic diseases often have a relapsing and remitting course with substantial impact on function and quality of life. Rheumatoid arthritis (RA) is considered a chronic, inflammatory autoimmune disorder that causes disabling and painful inflammation in the joints that can lead to detrimental effects on health-related quality of life (HRQOL). This article provides an overview of HRQOL and a comprehensive description of the attributes of different instruments to measure it. A wide variety of instruments have been created to measure HRQOL using 2 approaches: health status and health utility. Commonly used generic health status instruments in RA are the Medical Outcomes Study 36-Item Short Form (SF-36) and the Health Assessment Questionnaire Disability Index. Health utility measures are divided into 2 categories, direct and indirect. The most common direct health utility measures are the standard gamble, time to trade-off, and rating scale, while the most commonly used indirect measures are EuroQOL, SF-6D, and the Health Utility Index. Different applications of the instruments are analyzed in this article, including their utility to estimate burden of disease, as end points in clinical trials, and to monitor outcomes in clinical practice, as well as their uses in public policy and in individual decision making.