Clinical meaning can be assigned to scores of health status measures by using a variety of approaches. The anchor-based approach involves determining the difference on a quality of life (QOL) scale that corresponds to a self-reported small but important change on a global scale given concomitantly, which serves as an independent anchor. This article focuses on the anchor-based banding approach and reviews methods to assign clinical meaning to QOL measures, specifically the Dermatology Life Quality Index (DLQI) and Skindex. This article also includes pilot data that compares the DLQI and Skindex using these previously validated banding systems.
Skin disease is ubiquitous and can affect patients’ lives in various ways. The World Health Organization defines quality of life (QOL) as “the individuals’ perception of their position in life, in the context of the cultural and value system in which they live and in relation to their goals, expectations, standards and concerns.” Health-related QOL (HRQOL) includes the aspects of overall QOL that affect health: physical, psychological, and social. On an individual level, this includes health risks and conditions, functional status, social support, and socioeconomic status.
Several tools have been developed to assess the ways that skin disease is a burden to patients. This assessment is important because measuring HRQOL can help determine the burden of preventable disease and disability, help identify subgroups with poor perceived health, and help guide interventions to avoid more serious complications or burden. The functions of HRQOL assessment are numerous and include describing patients’ overall state; screening for early disease or disability; monitoring disease status, progression, and response to treatment; developing treatment plans; justifying the use of drugs that are expensive or have associated risk; improving patient-physician communication; and assisting in the allotment of limited resources.
HRQOL assessment is also important because physicians’ judgments of disease severity have been shown to not consistently correlate with patient-reported scores. Additionally, measurements that focus on the clinical severity of disease may not accurately reflect its effects on patients’ lives. For example, in a study of patients with psoriasis, HRQOL, rather than clinical severity of disease, was an independent predictor of work productivity. In these same patients, indirect costs of loss of productivity have been shown to clearly exceed the total direct cost; thus, savings from regaining work productivity might counterbalance the high costs of biologic agents.
Many skin-specific and skin disease–specific QOL instruments have been developed and validated to address the previously discussed needs. However, exceedingly few have explored the assignment of clinical meaning to the scores or changes in scores of the instrument. Currently, studies use statistical definitions (eg, P <.05) to claim a significant change in QOL after interventions. However, it is conceivable that a statistically significant change does not translate into a clinically significant change or a patient-oriented significant change. The most commonly used skin disease–specific instrument is the Dermatology Life Quality Index (DLQI), and it is the first to explore the issue of assigning a clinical meaning to DLQI scores. The other commonly used skin-specific instrument is the Skindex, for which investigators have also explored the assignment of clinical meaning. This article reviews the banding system, methods to assign clinical meaning to QOL measures, and specifically reviews methods behind the DLQI and Skindex scores. This article also includes pilot data that compare the DLQI and Skindex using these previously validated banding systems.
Dermatology Life Quality Index
The DLQI was the first dermatology-specific QOL assessment tool. Finlay and Kahn developed the DLQI in 1994 as a simple, practical questionnaire for routine clinical use. The DLQI is comprised of 10 questions that focus on disability in the following domains: symptoms and feelings, daily activities, leisure, work and school, personal relationships, and the effects of treatment on daily life. The questionnaire states that the aim is to measure the QOL impact over the previous 1 week. It has tick-box answers scored from 0 to 3, and the response options include the following: very much (score 3), a lot (score 2), a little (score 1), or not at all (score 0). Individual scores are added to yield a total score with a maximum of 30; a higher score indicates greater disability. The DLQI has been used in at least 36 skin conditions in 32 countries, is available in 55 languages, and has been described in more than 270 full articles. The most commonly assessed skin conditions using the DLQI are psoriasis, atopic dermatitis, acne, and vitiligo. The questionnaire usually takes less than 5 minutes to complete, with average completion time reported at 2 minutes.
Other than the original text-only version of the DLQI, there is also an illustrated version, which has a quicker average completion time of 88 seconds and has been shown to correlate strongly with the text-only version. Variants of the original DLQI include the Family Dermatology Life Quality Index and the Children’s Dermatology Life Quality Index.
The DLQI has been used widely for multiple purposes, including monitoring the effect of different therapeutic interventions, assessing the effectiveness of clinical practices and health services on patients’ QOL, and monitoring the efficacy of topical and systemic drugs. The DLQI has also been used in at least 2 national registers of psoriasis in the United Kingdom and Sweden. Additionally, the National Institute for Health and Clinical Excellence in the United Kingdom has incorporated a requirement of a DLQI score of greater than 10 to be eligible to start certain systemic therapies for psoriasis.
Multiple studies have proven that the DLQI has excellent psychometric properties, including validity, factor structure and dimensionality, internal consistency, sensitivity to change, and test-retest reliability. However, several weaknesses of the DLQI include the lack of incorporation of the aspect of worry or concerns regarding future health and the lack of assessment of itch-scratch problems and perceived stigmatization. There has also been some concern about item bias of the DLQI questions across variables, including gender, age, cultural background, diagnosis, and disease severity. The lack of incorporation of emotional or mental health aspects has led some to recommend the combination of the DLQI with assessments more geared at these emotional aspects, such as the Short Form-36 (SF-36), which contains a mental health summary measure ; in their review of QOL questionnaires for psoriasis, although the DLQI is not included, de Korte and colleagues also recommend the combination of the generic SF-36 with a dermatology-specific instrument to fully assess the QOL impact for dermatology patients.
Related posts:
Health-Related Quality of Life in Dermatology: Introduction and Overview
Overview of Health Status Quality-of-Life Measures
Quality-of-Life Issues in Vitiligo
Melasma Quality of Life Measures
Health-Related Quality-of-Life Assessment in Dermatologic Practice: Relevance and Application
Future Directions in Dermatology Quality of Life Measures
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