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.

(Am J Manag Care. 2007;13:S218-S223)

Chronic diseases often have a relapsing and remitting course with substantial impact on function and quality of life (QOL). For chronic illnesses where there is no cure, it is important to establish that therapy really makes people feel better. Thus, survival per se is no longer perceived to be the only end point; the goal is to improve, restore, or preserve QOL. The World Health Organization (WHO) defines QOL as an “individual’s perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns”¹ It is a broad-ranging concept affected by an individual’s physical health, psychological state, level of independence, social relationships, and their relationship to salient features of their environment.^1,2 QOL encompasses the concept of health-related quality of life (HRQOL) and other domains such as environment, family, and work. HRQOL is the extent to which one’s usual or expected physical, emotional, and social well-being are affected by a medical condition or its treatment.³ The HRQOL measurement therefore attempts to capture QOL in the context of one’s health and illness (Figure 1).⁴

Assessing Quality of Life

Work in HRQOL has originated from 2 fundamentally different approaches: health status and health value/preference/ utility assessment⁷ (Table 1 and Figure 2).^8,9 In general, health status measures describe a person’s functioning in 1 or more domains (eg, physical functioning or mental wellbeing). Currently, one of the most commonly used generic health status instruments (ie, the concepts are not specific for any age, disease, or treatment group) is the Medical Outcomes Study 36-Item Short Form (SF-36), a 36-item measure encompassing 8 domains—physical functioning, social functioning, mental health, role limitations due to physical problems, role limitations due to emotional problems, vitality (energy and fatigue), bodily pain, and general health perceptions—each of which is scored separately from 0 (worst) to 100 (best) (Table 2).¹⁰ The SF-36 domains can be summarized into physical component summary and mental component summary scores. By comparison, the most commonly used disease-specific instrument in rheumatoid arthritis (RA) is the Health Assessment Questionnaire Disability Index (HAQ-DI) a self-administered 20-question instrument that assesses a patient’s level of functional ability and includes questions on fine movements of the upper extremities, locomotor activities of the lower extremities, and activities that involve both the upper and lower extremities.¹¹ The HAQ-DI score is determined by summing the highest item score in each of the 8 domains and dividing the sum by 8, yielding a score ranging from 0 (no disability) to 3 (severe disability).

Direct Health Utilities.

An important advance in HRQOL research is the concept of minimum clinically important difference (MCID), defined as the smallest difference in score on an HRQOL instrument that patients perceive as beneficial and that would mandate, in the absence of troublesome side effects and excessive cost, a change in the patient’s management.²⁸ Differences in scores smaller than the MCID are considered unimportant, regardless of whether statistical significance is reached. For example, although an average change of 0.15 point on the HAQ-DI may be statistically significant in a clinical trial, it may not be perceived as meaningful by study subjects, so it would not meet MCID criteria. The MCID for the HAQ-DI in RA is 0.22 point^29,30; for various arthritides, the MCID for the SF-36 summary scores is 2.5 to 5.0 points, and on the individual SF-36 domain scores, the MCID is 5.0 to 10.0 points.^30-32 For indirect health utilities, MCIDs are generally 0.01 to –0.10.³³ MCID estimates of HRQOL measures have influenced designs of subsequent clinical trials aimed at improving HRQOL.³⁴

Applications of HRQOL Instruments

HRQOL is key in chronic (and acute) diseases. As such, HRQOL is considered an important outcome in arthritis clinical trials, and the US Food and Drug Administration (FDA) requires a sustained improvement in the HRQOL scores to file for an “improvement in HRQOL” claim. The FDA acknowledges that “not enough information is available on the performance of general HRQOL measures in longerterm arthritis trials (and) the incorporation of such measures in planned trials is encouraged.”³⁹ Similarly, further research and applications of HRQOL stand to improve patient care and benefit health policy.

DisclosureDr Khanna’s work was supported in part by the Scleroderma Foundation (New Investigator Award), a National Institutes of Health BIRCWH award (grant #HD051953), and the Scleroderma Clinical Trial Consortium. Dr Tsevat is supported in part by a National Center for Complementary and Alternative Medicine award (grant #K24 AT001676).

Address correspondence to: Dinesh Khanna, MD, MS, Assistant Professor of Medicine, Division of Rheumatology, Department of Medicine, David Geffen School of Medicine, 1000 Veterans Avenue, Rm 32-59 Rehabilitation Building, Los Angeles, CA 90095. E-mail: dkhanna@mednet.ucla.edu.

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