Why Quality of Life Is Measured

Today, most pediatric rheumatic diseases are not fatal. They affect children and their families by interfering with normal health, however, and they may have an impact on the enjoyment of life. Many of these diseases are not curable; in situations in which there is no cure, it is important to know that treatments, at least, make patients feel better. In the field of rheumatology, QoL has gained wide popularity because it has been shown to measure outcomes that are of direct interest and importance to patients, to provide effective measurements of patient status, to be predictive of patient outcome, and to produce reliable and effective measures of treatment impact.

Concepts of Structure and Function, Activity Limitation, Participation Restriction, Health, and Quality of Life

The terms used to describe the consequences of chronic health conditions have been unclear and overlapping. For this reason, the World Health Organization (WHO) developed the International Classification of Functioning and Health (ICF). The ICF provides a common vocabulary for the consequences of disease. This work followed from the WHO description of health as a biopsychosocial construct and the definition of QoL as an “individual’s perceptions 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.” The ICF framework is particularly applicable to rheumatic diseases.

According to the ICF model ( Fig. 7-1 ), a health condition affects an individual in three domains: (1) structures and functions (anatomy and physiology), (2) activities (e.g., activities of daily living), and (3) social participation. Each of these domains affects the others. For example, JIA might lead to muscle atrophy, weakness, cartilage erosion, joint contracture, and pain (structure and function domain). In addition, a child with JIA may not be allowed by his or her parents to run (activities domain) and not be allowed by his or her teacher to participate in school games (participation domain). In this example, joint pain, weakness, and contracture may also limit the ability to run, and this inability to run may be another reason why the child cannot participate in school games.

International Classification of Functioning and Health (ICF).

In the ICF model, each of the domains may be affected by personal factors and by environmental factors. Given the same level of anatomic and physiological damage, one child may be unable to attend school, whereas another more highly motivated child may be trying out for the basketball team. An example of environmental modification is the building of a ramp or other accessibility modifications so that a child who is a wheelchair user would be able to participate in a school dance.

QoL—which had been considered an additional domain in older models of health outcomes —is not defined in the ICF model. It is a term used ubiquitously in daily language and was originally applied by sociologists to try to determine the effect of material affluence on people’s lives. This sociological approach was developed in the United States during World War II. The concept broadened so that it eventually included education, social welfare, economics, and industrial growth. This broad societal approach was also incorporated into questionnaires that were developed to assess the status of an individual within this broad framework of concern.

Many of these areas of concern or domains, although important to an individual, are well outside the influence of disease and health care interventions. Also, QoL is considered to be a highly subjective construct, one that can be determined only by an affected individual based on the individual’s own goals and expectations and their personal evaluation of their current situation in many domains of life. For this reason, other terminology was developed to describe QoL, e.g., health-related quality of life (HRQoL), life satisfaction, self-esteem, well-being, general health, functional status, and life adjustment.

The earliest published uses of the term HRQoL date from the early 1980s. At that time, it was appreciated that medical interventions might only rarely have an impact on overall QoL, and thus HRQoL has been the term used most often to describe this construct. Tools purporting to measure HRQoL mostly measure symptoms (i.e., according to the patient) related to the ICF domains of structure and function, activities, and participation, and value these symptoms according to normative expectations (i.e., the values of groups of individuals rather than one individual). HRQoL can be defined as patient-reported “perceptions of health.”

For the purpose of this chapter, discussion of QoL is mostly restricted to HRQoL. HRQoL is a complex concept that contains numerous subcomponents. Experts differ as to what constitutes HRQoL, and consequently various instruments have been developed to measure it. These instruments may be divided into generic and disease-specific measures. Generic HRQoL measures are measures that purport to be broadly equal across different types and severity of disease, across different medical treatments or health interventions, and across different demographic or cultural subgroups. They are designed to capture aspects of health and disease that cross broad diagnostic categories and social or demographic subgroups. Disease-specific HRQoL measurements are designed to assess specific diseases or patient populations; such instruments are usually more responsive to changes in individual subject status. The past 30 years have seen the development and validation of various instruments to measure the various ICF domains and generic and disease-specific HRQoL. These instruments were first developed in adult rheumatology, but in the past 25 years tools specifically designed to be used in pediatric rheumatic diseases have been developed.

Hierarchy of Outcomes

The ICF framework can be used to structure a hierarchy of outcomes. The first level of outcome assessment is within the domain of structure and function. Most measures of “disease activity” fit in this domain. Disease activity measures include parameters most familiar to clinicians, such as joint counts, morning stiffness, and erythrocyte sedimentation rate. The major drawback to measures in this area is that they are not directly what the patient is interested in. Measures of disease activity are still widely used in clinical trials, however, because inhibition of the disease process or activity is an essential component of an effective therapeutic intervention. At this time, measurement of disease activity is a necessary but insufficient approach to measuring patient outcome. When the performance characteristics of the traditional disease activity measures used in rheumatology were scientifically assessed, many instruments have been found to be unreliable, redundant, insensitive to change, or not correlated with long-term patient outcome. For example, even experienced clinicians often disagree when assessing joint count.

The next level up the hierarchy is the measurement of activity and activity limitation and social participation. This domain reflects physical function and disability and social handicaps. The focus here is on measuring the ability of the person to perform physical activities of daily life, such as dressing, walking, climbing stairs, and self-care, and to participate meaningfully in society. This is an area of more relevance to the patient and reflects the view of the WHO that health is a state of physical, mental, and social well-being. Disease-specific HRQoL measures, such as the Health Assessment Questionnaire (HAQ) and the Arthritis Impact Measurement Scale (AIMS), were developed to incorporate the broad WHO concept of health. Despite concerns regarding the ability to measure QoL in children, major advances have been made in the development and validation of disease-specific HRQoL tools for children with rheumatic diseases. These instruments are discussed later.

The highest level in the hierarchy is the measurement of overall QoL. Overall QoL is affected by many life issues and events that do not clearly relate to health. According to the WHO, QoL “reflects the view that quality of life refers to a subjective evaluation, which is embedded in a cultural, social, and environmental context.” Because a QoL measure “focuses upon respondents’ ‘perceived’ quality of life, it is not expected to provide a means of measuring in any detailed fashion symptoms, diseases or conditions, nor disability as objectively judged, but rather the perceived effects of disease and health interventions on the individual’s quality of life. [It] is, therefore, an assessment of a multi-dimensional concept incorporating the individual’s perception of health status, psycho-social status and other aspects of life.”

Although overall QoL can be measured, it is unclear how its measurement can contribute to health care. With this in mind, the development of a core set of measures for application in clinical trials in pediatric rheumatic diseases (JIA, SLE, and JDM ) has been very influential. These core sets incorporate the types of instruments already alluded to, but focus largely on the measurement of disease activity ( Table 7-2 ).

Childhood Arthritis Impact Measurement Scales

CHAIMS was the first disease-specific measure developed for JIA. This was a modification of the AIMS. Its measurement properties were poor, however, except for the pain dimension, and, as a result, it has not been used widely.

Childhood Health Assessment Questionnaire

The CHAQ was derived from the adult HAQ. It comprises two indices: Disability and Discomfort. The Disability Index assesses function in eight areas distributed among a total of 30 items: (1) dressing and grooming, (2) arising, (3) eating, (4) walking, (5) hygiene, (6) reach, (7) grip, and (8) activities. In each functional area, there is at least one question that is relevant to children of all ages. Each question is rated on a 4-point scale of difficulty in performance, scored from 0 to 3. The Disability Index is calculated as the mean of the eight functional areas. Discomfort is determined by the presence of pain, as measured by a 100-mm visual analog scale (VAS). In the original validation study, mean scores for patients were 0.84 for the Disability Index and 0.82 for the Discomfort Index. Reliability was very good. Convergent validity was also very good, with excellent correlations with Steinbrocker’s functional class, active joint count, disease activity index, and degree of morning stiffness. Mean scores for parents and children were not significantly different from one another and were highly correlated, suggesting that parents can reliably report for their children. CHAQ was completed by parents in all cases and by children 8 years and older in a mean of 10 minutes. Responsiveness was established later.

CHAQ has been shown to be a useful instrument for outcome evaluation in longitudinal studies. It has also been used in a variety of settings, translated into many different languages and undergone modifications in attempts to improve it while still maintaining excellent reliability, validity, and parent–child correlations. Although one study suggested that it had poor responsiveness, good responsiveness has been shown in other studies, including several longitudinal studies of etanercept. Several studies have shown its usefulness in the evaluation of rehabilitative interventions. Other studies suggest that it is highly predictive of the presence of significant pain, and to be highly predictive of short-term outcomes in a large cohort of Canadian children. Scores of 0.13, 0.63, and 1.75 represent mild, mild to moderate, and moderate disability, whereas the minimum clinically important change score (MCID) for improvement is −0.188; for deterioration it is +0.125. A recent study suggests that removal of aids or devices from the scoring does not alter the interpretation of the Disability Index, and thus removal of the aids and devices provides a simplified questionnaire that is a more effective alternative. A digital form developed and validated in a Dutch population was declared to be user friendly.

CHAQ has excellent reliability and validity and reasonable responsiveness. It also has good discriminative properties and can be administered to children of all ages; it is of great use in the clinical setting for long-term follow-up of children with JIA. CHAQ is valuable for longitudinal studies and clinical trials and has become the preferred measure in both settings. Some attempts have been undertaken to modify it, but the original version is still used in most studies.

Juvenile Arthritis Functional Assessment Scale and Report

JAFAS is an observer-based scale, whereas JAFAR is completed by the patient or parent. Items for both instruments were derived from the AIMS, HAQ, and McMaster Health Index Questionnaire.

JAFAS requires standardized simple equipment and can be administered in about 10 minutes by a health professional who times the child’s performance on 10 physical tasks. Good reliability and convergent validity have been shown. JAFAR comprises one dimension and contains 23 items that assess ability to perform physical tasks in children older than 7 years on a 3-point scale scored from 0 to 2; the score range is 0 to 46, with the lower score indicating better function. Two separate versions are available, one for the child (JAFAR-C) and one for the parents (JAFAR-P). Reliability is good for both versions. Construct validity is also good, with predictable correlations among JAFAR-C, JAFAR-P, JAFAS, and pain, and moderate correlations with measures of disease activity. Similar measurement properties were found in an English study. A Dutch translation of JAFAR also showed good measurement properties. Responsiveness was shown in a small trial of intravenous immunoglobulin in polyarticular JIA. JAFAR has also proved to be a useful measure of functional ability in studies on osteopenia and sleep disturbance in JIA.

JAFAR has excellent reliability and validity, but limited responsiveness. It cannot be administered to children younger than 7 years, and this prohibits its use in children with early-onset of JIA. Nonetheless, it is a practical instrument that is useful in the clinical setting and in the longitudinal follow-up of most children with JIA.

Juvenile Arthritis Self-Report Index

JASI was developed with a specific focus on physical activity in children older than 8 years with JIA. Its emphasis is on responsiveness, and it is aimed primarily at evaluation of rehabilitation interventions. Through a detailed process, an instrument with 100 items was developed, divided into five categories of physical function: (1) self-care, (2) domestic, (3) mobility, (4) school, and (5) extracurricular. In JASI Part 2, patients identify up to five tasks that are most problematic, and these tasks are evaluated on subsequent follow-up. This maneuver makes this component of JASI potentially more responsive and patient specific. In a validation study, JASI was shown to have good measurement properties. There was reasonable spread of scores, suggesting that JASI has discriminative ability. Reliability was shown with excellent intraclass correlations. Construct validity was established by demonstration of predicted correlations with other measures used.

Although JASI is an excellent instrument, it cannot be administered to children younger than 8 years of age. Also, it takes a long time to complete, and this may make it less attractive for routine clinical use. Nonetheless, JASI is a comprehensive instrument with excellent measurement properties whose greatest value is probably as a research tool for longitudinal studies or to help identify specific goals in a rehabilitation setting.

Juvenile Arthritis Quality of Life Questionnaire

JAQQ was developed by following standard principles of item generation, a process that has demonstrated a very high level of agreement between patients and parents over a wide array of perceived difficulties. Additional items on psychosocial function were added by the incorporation of a previously developed psychosocial instrument.

Generated items were subsequently reduced and categorized into four dimensions, each with approximately 20 items: (1) gross motor function, (2) fine motor function, (3) psychosocial function, and (4) general symptoms. Respondents score all items and are asked to identify up to five items in each dimension with which they are having difficulty; they may also volunteer their own items for each dimension. The mean score for the five highest scoring items in each dimension is computed as the Dimension Score (range, 1 to 7); the Total JAQQ Score is computed as the mean of the four Dimension Scores (range, 1 to 7).

After this initial study, the item number was reduced to 74: gross motor function, 17 items; fine motor function, 16 items; psychosocial function, 22 items; and general symptoms, 19 items. A pain dimension was added as a supplement. Face, content, and construct validity were clearly established. Responsiveness was established after the start of new drug therapy. Responsiveness was also shown to be maintained over time and to be at least as good as responsiveness of CHAQ, CHQ, or Peds QL. Enhancement of responsiveness was shown by a reduction in the number of items scored, and in this study MCID was shown to be 0.35.

JAQQ has been translated into several languages and has been shown to maintain its measurement properties in several different cultural settings. In an English study of adolescents with JIA, JAQQ was shown to have excellent reliability and validity. In a further study, the same group showed improvement in JAQQ scores, with excellent responsiveness, after the introduction of a transitional care program. A high level of agreement between the perception of children with JIA and their parents concerning HRQoL was shown in a Canadian study. Another more recent Canadian study showed that JAQQ was highly predictive of several short-term outcomes in a large cohort of children with JIA.

JAQQ has been developed in a detailed fashion, resulting in excellent measurement. It can be administered to children of all ages and disease onset types in a reasonable time with minimal assistance, and it can be scored quickly by hand; this makes it practical for use in the clinical setting.

Childhood Arthritis Health Profile

CAHP is a parent report that is self-administered and consists of three modules: (1) generic health status measures, (2) JIA-specific health status measures, and (3) patient characteristics. Three functional scales were determined for the JIA-specific scales: (1) gross motor function, (2) fine motor function, and (3) role activities (play, family, friends). Internal reliability was shown by good inter-item correlations within scales and minimal item scale variation. Correlation coefficients for the JIA-specific scales with one another ranged from 0.84 to 0.97, whereas those for the generic functioning scales were 0.73, showing validity of these scales and further suggesting that the JIA-specific scales provide additional information beyond that of the generic functioning scales. In a follow-up report, the discriminative ability of CAHP was demonstrated.

Quality of My Life Questionnaire

QoMLQ was developed in an attempt to distinguish between difficulties resulting from the disease itself and difficulties that are more generic. It comprises two separate 100-mm VAS, anchored with the descriptors “worst” and “best,” that direct respondents to indicate their “quality of life,” in aspects caused by the disease itself (HRQoL) and those caused by overall difficulties not directly related to the disease (QoL). In a further study that included 131 parent–child pairs, there was a high level of agreement between parents and children for QoL and moderate agreement for HRQoL. In this study, there were good correlations for components with pain and disease severity, establishing its convergent construct validity. Also, MCID for improvement in QoL and HRQoL were 7 mm and 11 mm, and for deterioration were −33 mm and −38 mm, respectively, providing the opportunity for clinicians to interpret changes in scores.

QoMLQ is a short and easy-to-use generic instrument that has been shown to be highly reliable and valid. Given these qualities, it is likely to see more widespread use.

In further work from the same group, a novel approach was used in attempting to measure the gap between an individual’s current situation and their expectations, in some respects an extension of the work alluded to earlier. Contemporary measures of QoL tend not to take this “gap” into consideration. This study attempted to measure these gaps for a whole series of domains in children with rheumatic diseases. The result was the development of a measure with 72 items distributed among 5-gap scales (GapS). The GapS are currently undergoing further development.

Child Health Questionnaire

CHQ is a generic instrument that comprises numerous different forms. The form used most commonly in children with JIA is the Parent Form 50 (PF 50), which contains 50 items distributed in several dimensions: global health, physical activities, everyday activities, pain, behavior, well-being, self-esteem, general health, and family. These sections are complemented by general questions about the child and the caregiver. Two separate scores can be computed that estimate physical and psychosocial function; both are scored from 0 to 100, with the higher score indicating better function.

In a study of short-term outcome in 116 children with JIA observed for less than 2.5 years, Selvaag and colleagues showed poorer physical status but minimal psychological impairment in JIA patients relative to controls using CHQ. Numerous studies from the Pediatric Rheumatology International Trials Organization (PRINTO), which has validated CHQ for use in 32 languages, disagree with this study, however. In one study that included 6639 participants (one half had JIA, and one half were healthy), mean scores for physical and psychosocial summary scores were significantly lower for JIA patients relative to controls. In a further study that included three distinct geographical regions (Eastern Europe, Western Europe, and Latin America), determinants of poor HRQoL were similar across all regions, with physical well-being affected by the level of disability and psychosocial well-being affected by the intensity of pain. CHQ was used in combination with CHAQ in a trial of methotrexate, in which it was shown to be highly responsive ; this was further confirmed in a follow-up study of the same study group. One study suggested, however, that JAQQ may be at least as responsive as CHQ for studies in JIA. Because of its generalizability, CHQ has become the preferred measure of QoL for JIA trials.

Pediatric Quality of Life Inventory

Peds QL is a modular instrument designed to measure HRQoL in children and adolescents 2 to 18 years old. It contains a generic core integrated with a disease-specific core. The generic core has undergone various iterations, the most recent of which—the Peds QL 4.0 Generic Core Scales—contains 23 items distributed in four scales: (1) physical, (2) emotional, (3) social, and (4) school functioning. The Peds QL 3.0 Rheumatology Module contains 22 disease-specific items distributed in five scales: (1) pain, (2) daily activities, (3) treatment, (4) worry, and (5) communication. It is completed by children and their parents, and consists of developmentally appropriate forms for varying age groups. When it is completed separately, parent–child concordance has been shown to be good. The module takes approximately 15 minutes to complete. Each item is scored on a 5-point scale (0 to 4), with a higher score indicating worse function. A mean Scale Score is computed based on the number of items scored. This score is extrapolated in a reverse fashion to a scale of 0 to 100, with a higher score indicating better function. Total Scale Scores are computed as the mean across all items scored in that scale. This process is the same for the Generic Core Scale and the Rheumatology Module.

This instrument was shown to have excellent reliability, validity, and responsiveness in a study of 271 children with various rheumatic diseases (91 of whom had JIA) and their parents. Reliability varied with the age of the child, being less for younger children. Reliability was also not as good for the Rheumatology Module.

Lower HRQoL, as exemplified by lower Peds QL generic and rheumatology module scores, was noted in one study, despite minimal symptoms or little or no disease activity, whereas another study showed significantly reduced scores in children with polyarticular JIA, particularly in fatigue scores. A further study showed lower Peds QL scores for Medicaid patients even when correcting for health care use and degree of disease activity.

Responsiveness has not been tested in a trial setting. Nonetheless, this instrument represents an important addition to the pool of outcome measures available for use in JIA, and further studies are being followed with interest.