Overview of Health Status Quality-of-Life Measures




The concept of quality of life (QOL) is becoming increasingly important in medicine, particularly in dermatology where many cutaneous diseases have the potential to affect the quality rather than the length of life. There is increasing interest in devising methodology to accurately measure the impact of disease on QOL for use in clinical practice, research studies, and economic analyses. The question of which dermatologic QOL instruments to choose inevitably arises. The aim of this article is to familiarize readers with health status measures and to review their use in dermatology.


The concept of quality of life (QOL) is becoming increasingly important in medicine, particularly in dermatology where many cutaneous diseases have the potential to affect the quality rather than the length of life. As such, there has been increasing interest in devising methodology to accurately measure the impact of disease on QOL for use in clinical practice, research studies, and economic analyses. The aim of this article is to familiarize readers with health status QOL instruments and to review their use in dermatology.


There are several instruments used to capture the impact of disease on QOL, which can be categorized into 2 principal categories: preference-based measures and health status QOL assessments. Preference-based measures are derived from decision-making theory and determine patient preferences for a specific health state by inviting patients to hypothetically give up something of value, such as money, years of life, and so forth. A detailed discussion of preference-based measures can be found in the article by Seidler and colleagues elsewhere in this issue. In contrast, health status QOL measures capture the impact of disease on various dimensions of QOL, such as the cognitive, social, and emotional aspects, as well as physical discomfort and limitations. Of note, the authors acknowledge that some investigators distinguish between “health status” and “health-related quality of life” as discussed in the introduction to this issue. Here, the authors use the term “health status QoL” to distinguish from preference-based measures. For the purposes of this discussion, the authors are loosely combining both instruments that focus more on disability (health status) with those that integrate the psychosocial aspects (health-related QoL). The dimensions that compose health status are well established and make up the conceptual framework on which many health status QOL measures are based. Health status QOL measures quantitatively represent the impact of disease on health status through a single summary score or a profile of interrelated subscale scores. A college-aged female patient with psoriasis might consider her skin condition more burdensome than an 85-year-old man with the same skin condition who is less concerned with his appearance. Health status QOL instruments allow distinguishing between individuals who may bear the same skin pathology but experience different burden of disease. Health status measures can generally be classified into 3 main categories: generic, dermatology-specific, and condition-specific instruments, which are discussed in detail.


In 2002, the United States Congress requested further investigation by the National Institute of Arthritis and Musculoskeletal and Skin Disease (NIAMS) into the burden of skin disease. In response, the NIAMS sponsored the Workshop on the Burden of Skin Disease in 2002 to discuss elements that compose the burden of skin diseases and their impact on public health and daily living. One of the project recommendations from this working group was a need for additional adult skin–specific QOL instruments for the more prevalent skin diseases that capture not only the symptomatic but also the functional, psychological, social, and emotional impact of skin disease. Additionally, the development of skin-specific QOL measures for children and family impact was recommended to characterize QOL impact more comprehensively.


In 2007, a NIAMS-funded working group published a summary of their work in response to the Workshop’s recommendation. They systematically and comprehensively searched for all available health status QOL instruments that had been either applied to or developed for skin diseases. They found a total of 40 health status QOL instruments: 6 generic, 11 adult skin specific, and 15 adult condition specific. This article does not seek to be comprehensive like the 2007 effort. Rather, it highlights the most commonly used generic, skin-specific, and condition-specific health status measures for dermatology and summarizes the appropriate usage of these instruments.


Considerations in selecting a health status QOL instrument


Although there is no simple formula for selecting a health status QOL measure, there are several considerations in deciding which health status QOL instrument is most appropriate for use. The setting, time course, and psychometric properties of the instrument are all factors in guiding questionnaire selection.


Although the use of QOL measures in routine clinical practice has been sparse, in recent years there has been increased interest in the use of QOL assessments in clinical settings to prioritize problems, evaluate physical or psychosocial problems that might otherwise be overlooked, monitor the therapeutic process and assess treatment outcomes, and improve clinical care. In the clinical setting, measures that are concise, have a straightforward scoring system, and are dermatology specific or condition specific may be most useful to clinicians.


The use of health status QOL instruments in clinical research is dependent on the specific aim of the study itself. If the purpose is to evaluate treatment outcomes of a therapy, condition-specific measures may be most sensitive in capturing the small changes in therapeutic response. If the purpose is to compare different skin diseases, the use of a dermatology-specific instrument alone or in conjunction with a condition-specific instrument may be more appropriate. In health-economic analyses, the use of generic health status QOL measurements, alone or in conjunction with a dermatology or condition-specific measure, is necessary to compare burden of dermatologic disease with non-dermatologic pathology.


Although time constraints may not be as much of a concern in clinical research or economic analyses, care should be taken to consider the total time required to answer a questionnaire, particularly when multiple instruments are administered. The accuracy of completion of questionnaires likely wanes as more questionnaires are administered.


The time course over which health status is assessed is also an important consideration. Some health status QOL instruments assess only the day of completion itself. Although this allows for an accurate assessment of a patient’s symptoms in real time, the disadvantage of only assessing symptoms “today” or “currently” is that this only provides a brief snapshot of burden of disease. This may be appropriate for chronic diseases where the symptoms occur daily with little fluctuation but may be less relevant for diseases that are relapsing and remitting in nature. Questionnaires that provide a longer time course, such as 1 week or 4 weeks, may be more reasonable alternatives. If an instrument is re-administered for meaningful comparison, the frequency of administration should not be less than the time course used.


In addition, the psychometric properties of the measurement tools themselves must be considered. The primary properties used to evaluate health status instruments are reliability, validity, and responsiveness.


Reliability


Reliability is the degree to which an instrument is free from random error. That is, the more reliable an instrument, the more it produces the same results when used repeatedly under the same conditions. Two types of reliability are considered important with regard to health status QOL measures: test-retest reliability and internal consistency reliability. Test-retest reliability is the degree to which an instrument yields stable scores over time among respondents who are assumed not to have changed with regard to the domains assessed. The correlation is usually expressed by an intraclass correlation coefficient (ICC). An ICC greater than 0.70 is desirable for group comparisons and 0.90 to 0.95 is desirable for individual measurements over time.


Internal consistency reliably reflects the extent to which all items of a questionnaire address the same theoretic construct. A questionnaire is considered internally consistent when there is a high intercorrelation among the item scores. The intercorrelation is usually expressed by the Cronbach α coefficient. Commonly acceptable standards for reliability coefficients, similar to ICC, are 0.70 for group comparisons and 0.90 to 0.95 for individual comparisons.


Validity


Validity is the degree to which a questionnaire measures what it intends to measure. Validity is particularly important with respect to the language, cultural, and clinical settings in which an instrument was developed—an instrument validated in one language or in a specific population may not be valid in other groups. Revalidation may be necessary in a new environment. Although there are many types of validity, those most commonly used for testing the psychometrics of dermatology health status QOL measures are content validity and construct validity.


Content validity is defined as the extent to which the content of an instrument is appropriate for its intended use. The items should adequately represent the entire construct measured and questions should be clear and free of redundant items. For example, when generic measures are used in dermatology, they generally have lower content validity in comparison with dermatology-specific measures since they contain items not applicable to dermatology patients.


Construct validity is the degree to which a questionnaire agrees with a priori theorized constructs. The RosaQoL, a rosacea-specific QOL instrument, was theorized to measure three constructs: symptom, emotional, and functional impairment of rosacea. Using principal components analysis, the three main factors correlated to the three main theorized constructs with statistical significance—indicating that the RosaQoL actually measures the three domains as was intended.


Responsiveness


Responsiveness to change is the extent to which a questionnaire can be used to detect changes over time. Responsiveness is supported when a measure can detect differences in outcomes even if those differences are small. Common methods of assessing responsiveness include comparing scale scores before and after an intervention expected to affect the construct and comparing changes in scale scores with changes in other related measures assumed to move in the same direction as the target measure. Condition and dermatology-specific measures are more sensitive to small changes in disease status and are generally regarded as more responsive than generic measures.


Selecting the appropriate instrument often involves trade-offs between short, simple measures and lengthier more comprehensive measures in terms of reliability, validity, and responsiveness.




Generic health status QOL measures


Generic measures ( Table 1 ) are designed to comprehensively capture the many aspects of health as it relates to QOL in different diseases, patients, and populations of health status. As such, generic instruments have the advantage that they can be applied across varying types and severity of disease, medical treatments or therapeutic interventions, and demographic and cultural subgroups.



Table 1

Generic health instruments and their properties


































Generic Health Instrument Number of Questions Time (min) for Administration Health Domains Advantages/Disadvantages
MOS 36-Item Short Form Health Survey (SF-36) 36 5 to 10


  • Physical functioning



  • Role limitations due to physical problem



  • Bodily pain



  • General health



  • Vitality



  • Social functioning



  • Role limitations due to emotions



  • Mental health



  • Health transition

Considered the most studied and well-validated instrument available and the reference instrument by most researchers. Applicable across a broad range of clinical conditions. Structure and restest reliability are controversial.
Sickness Impact Profile (SIP) 136 20 to 30


  • Physical Dimension



  • Ambulation



  • Mobility



  • Body care and movement




  • Psychosocial Dimension



  • Communication



  • Alertness behavior



  • Emotional behavior



  • Social interaction




  • Independent Categories



  • Sleep and rest



  • Eating



  • Work



  • Home management



  • Recreation and pastimes

Long time for completion, focused on disability
Nottingham Health Profile (NHP) 38 10 to 15


  • Energy level



  • Emotional reactions



  • Physical mobility



  • Pain



  • Social isolation



  • Sleep

Easy to administer
WHOQOL-100 100 20 to 30


  • Physical



  • Psychological



  • Level of independence



  • Social relationships



  • Environment



  • Spirituality

Truly cross-culturally equivalent


Although generic measures may have robust psychometric properties, they may suffer from low content validity because they contain items of little or no relevance to dermatology patients. As such, they may not detect small changes in QOL and thus are not helpful in following dermatologic impact across time in the clinical or research setting. Because of these issues, generic health instruments should be used in a limited capacity. One scenario where they may be helpful is if a clinician or researcher wants to compare a dermatologic condition with a nondermatologic condition in terms of QOL impact. The other scenario is to use a generic QOL instrument in conjunction with dermatology-specific or condition-specific instruments when the skin condition in question has substantial health-related QOL impact beyond the disease specific impact. For example, Sampogna and colleagues compared results from the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) with dermatology-specific instruments (discussed later), the Skindex-29 and Dermatology Life Quality Index (DLQI), in psoriasis patients and concluded that generic QOL instruments (eg, the SF-36) served as a useful adjunct to dermatology-specific questionnaires and allowed for a more comprehensive assessment of burden in psoriasis patients than would otherwise have been gained from using dermatology-specific instruments alone. This article reviews 4 of the more common generic QOL instruments that have been applied to dermatology. The decision to select of these 4 instruments should be based on the construct and domains that the instrument covers and if the instrument has been applied to the dermatologic disease in question. The latter criteria allow clinician/researchers to compare their data with those of a previous population with the same skin condition.


The Sickness Impact Profile (SIP) is a 136-item measure developed in the United States to provide a broad measure of disease impact on physical and emotional functioning. The SIP assesses disability due to disease across 12 domains: physical (ambulation, mobility, and body care/movement) and psychosocial dimensions (social interaction, communication, alertness behavior, emotional behavior, sleep, eating, home management, recreation, and work). The SIP percentage score can be calculated for the total instrument (an index score) or for each domain, where 0 indicates better health and 100 worse health status. Two summary scores, a physical function and psychosocial function, may also be calculated. The instrument may be self-administered or interview-administered. An abbreviated version of the SIP with 68 items, the SIP68, has been developed. The SIP has been used in psoriasis, atopic dermatitis, acne, and basal cell carcinoma.


The Nottingham Health Profile (NHP) was developed in the United Kingdom in the 1970s. Part I of the NHP contains 38 items that cover 6 domains of experience (physical ability, energy level, emotional reaction, sleep, social isolation, and pain) with individual scores for each domain. Part II of the NHP contains statements about areas of daily life most often affected by health. Results are analyzed by summing the number of positive responses in a dimension or weighting items to calculate a dimension score (range 0–100). The instrument may be administered by self, interviewer, or via telephone. The NHP has been used in patients with psoriasis, palmar hyperhydrosis, chronic urticaria, chronic leg ulcers, and herpes zoster.


The SF-36 is designed for use in clinical practice and research, health policy evaluations, and general population surveys. The questionnaire contains 36 items measuring 8 dimensions: physical functioning, emotional role functioning, physical role functioning, social role functioning, mental health, vitality, bodily pain, and general health perception. The 8 dimensions of the SF-36 can be combined into 2 summary scores, the physical component score and the mental component score. Scoring is on a 100-point scale with a change of 5 points considered clinically significant. The SF-36 has been used in psoriasis, acne, and atopic dermatitis, chronic urticaria and has been demonstrated to enhance the information derived from dermatology-specific questionnaires. Abbreviated versions of the SF-36, including the 20-Item Short Form Health Survey (SF-20) and 12-Item Short Form Health Survey (SF-12), were developed from the SF-36 for use in large surveys and longitudinal studies. Seven items of the SF-12 correspond to the physical component score whereas 5 comprise the mental component score. The SF-12 has been used in dermatology, albeit less than the SF-36, in studies of hyperhidrosis, atopic dermatitis, onychomycosis, alopecia, nonmelanoma skin cancer oral mucosal conditions, and melisma.


The WHOQOL-100 is a 100-item questionnaire developed in 1994 by the World Health Organization that evaluates QOL in 6 domains: physical, psychological, level of independence, social relationships, environment, and spirituality. The WHOQOL-100 was developed with the aim of being able to identify aspects of QOL that are cross-culturally important and has been used in studies around the world. Compared with the SF-36, the WHOQOL-100 has demonstrated good concurrent validity, greater comprehensiveness, and very good responsiveness to clinical change in a cohort of chronic pain patients and has proved a valuable instrument for measuring QOL in depressed patients.


The WHOQOL-BREF is a more concise 26-item questionnaire with 2 items dedicated to assessing overall health and the remaining items adapted from the physical, psychological, social relations, and environment domains of the WHOQOL-100. The WHOQOL-100 has been used in psoriasis and the WHOQOL-BREF in atopic dermatitis, acne, chronic urticaria, melasma, and vitiligo.




Generic health status QOL measures


Generic measures ( Table 1 ) are designed to comprehensively capture the many aspects of health as it relates to QOL in different diseases, patients, and populations of health status. As such, generic instruments have the advantage that they can be applied across varying types and severity of disease, medical treatments or therapeutic interventions, and demographic and cultural subgroups.



Table 1

Generic health instruments and their properties


































Generic Health Instrument Number of Questions Time (min) for Administration Health Domains Advantages/Disadvantages
MOS 36-Item Short Form Health Survey (SF-36) 36 5 to 10


  • Physical functioning



  • Role limitations due to physical problem



  • Bodily pain



  • General health



  • Vitality



  • Social functioning



  • Role limitations due to emotions



  • Mental health



  • Health transition

Considered the most studied and well-validated instrument available and the reference instrument by most researchers. Applicable across a broad range of clinical conditions. Structure and restest reliability are controversial.
Sickness Impact Profile (SIP) 136 20 to 30


  • Physical Dimension



  • Ambulation



  • Mobility



  • Body care and movement




  • Psychosocial Dimension



  • Communication



  • Alertness behavior



  • Emotional behavior



  • Social interaction




  • Independent Categories



  • Sleep and rest



  • Eating



  • Work



  • Home management



  • Recreation and pastimes

Long time for completion, focused on disability
Nottingham Health Profile (NHP) 38 10 to 15


  • Energy level



  • Emotional reactions



  • Physical mobility



  • Pain



  • Social isolation



  • Sleep

Easy to administer
WHOQOL-100 100 20 to 30


  • Physical



  • Psychological



  • Level of independence



  • Social relationships



  • Environment



  • Spirituality

Truly cross-culturally equivalent


Although generic measures may have robust psychometric properties, they may suffer from low content validity because they contain items of little or no relevance to dermatology patients. As such, they may not detect small changes in QOL and thus are not helpful in following dermatologic impact across time in the clinical or research setting. Because of these issues, generic health instruments should be used in a limited capacity. One scenario where they may be helpful is if a clinician or researcher wants to compare a dermatologic condition with a nondermatologic condition in terms of QOL impact. The other scenario is to use a generic QOL instrument in conjunction with dermatology-specific or condition-specific instruments when the skin condition in question has substantial health-related QOL impact beyond the disease specific impact. For example, Sampogna and colleagues compared results from the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) with dermatology-specific instruments (discussed later), the Skindex-29 and Dermatology Life Quality Index (DLQI), in psoriasis patients and concluded that generic QOL instruments (eg, the SF-36) served as a useful adjunct to dermatology-specific questionnaires and allowed for a more comprehensive assessment of burden in psoriasis patients than would otherwise have been gained from using dermatology-specific instruments alone. This article reviews 4 of the more common generic QOL instruments that have been applied to dermatology. The decision to select of these 4 instruments should be based on the construct and domains that the instrument covers and if the instrument has been applied to the dermatologic disease in question. The latter criteria allow clinician/researchers to compare their data with those of a previous population with the same skin condition.


The Sickness Impact Profile (SIP) is a 136-item measure developed in the United States to provide a broad measure of disease impact on physical and emotional functioning. The SIP assesses disability due to disease across 12 domains: physical (ambulation, mobility, and body care/movement) and psychosocial dimensions (social interaction, communication, alertness behavior, emotional behavior, sleep, eating, home management, recreation, and work). The SIP percentage score can be calculated for the total instrument (an index score) or for each domain, where 0 indicates better health and 100 worse health status. Two summary scores, a physical function and psychosocial function, may also be calculated. The instrument may be self-administered or interview-administered. An abbreviated version of the SIP with 68 items, the SIP68, has been developed. The SIP has been used in psoriasis, atopic dermatitis, acne, and basal cell carcinoma.


The Nottingham Health Profile (NHP) was developed in the United Kingdom in the 1970s. Part I of the NHP contains 38 items that cover 6 domains of experience (physical ability, energy level, emotional reaction, sleep, social isolation, and pain) with individual scores for each domain. Part II of the NHP contains statements about areas of daily life most often affected by health. Results are analyzed by summing the number of positive responses in a dimension or weighting items to calculate a dimension score (range 0–100). The instrument may be administered by self, interviewer, or via telephone. The NHP has been used in patients with psoriasis, palmar hyperhydrosis, chronic urticaria, chronic leg ulcers, and herpes zoster.


The SF-36 is designed for use in clinical practice and research, health policy evaluations, and general population surveys. The questionnaire contains 36 items measuring 8 dimensions: physical functioning, emotional role functioning, physical role functioning, social role functioning, mental health, vitality, bodily pain, and general health perception. The 8 dimensions of the SF-36 can be combined into 2 summary scores, the physical component score and the mental component score. Scoring is on a 100-point scale with a change of 5 points considered clinically significant. The SF-36 has been used in psoriasis, acne, and atopic dermatitis, chronic urticaria and has been demonstrated to enhance the information derived from dermatology-specific questionnaires. Abbreviated versions of the SF-36, including the 20-Item Short Form Health Survey (SF-20) and 12-Item Short Form Health Survey (SF-12), were developed from the SF-36 for use in large surveys and longitudinal studies. Seven items of the SF-12 correspond to the physical component score whereas 5 comprise the mental component score. The SF-12 has been used in dermatology, albeit less than the SF-36, in studies of hyperhidrosis, atopic dermatitis, onychomycosis, alopecia, nonmelanoma skin cancer oral mucosal conditions, and melisma.


The WHOQOL-100 is a 100-item questionnaire developed in 1994 by the World Health Organization that evaluates QOL in 6 domains: physical, psychological, level of independence, social relationships, environment, and spirituality. The WHOQOL-100 was developed with the aim of being able to identify aspects of QOL that are cross-culturally important and has been used in studies around the world. Compared with the SF-36, the WHOQOL-100 has demonstrated good concurrent validity, greater comprehensiveness, and very good responsiveness to clinical change in a cohort of chronic pain patients and has proved a valuable instrument for measuring QOL in depressed patients.


The WHOQOL-BREF is a more concise 26-item questionnaire with 2 items dedicated to assessing overall health and the remaining items adapted from the physical, psychological, social relations, and environment domains of the WHOQOL-100. The WHOQOL-100 has been used in psoriasis and the WHOQOL-BREF in atopic dermatitis, acne, chronic urticaria, melasma, and vitiligo.

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Feb 12, 2018 | Posted by in Dermatology | Comments Off on Overview of Health Status Quality-of-Life Measures

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