Juvenile idiopathic arthritis (JIA) is a chronic and heterogeneous disease characterized by prolonged synovial inflammation that may lead to permanent alterations in joint structures. Permanent changes may also develop in extraarticular organs/systems, such as the eye (as a complication of chronic anterior uveitis) or the kidney (due to systemic amyloidosis), or may result from side effects of medications (1). This morbidity may have a relevant impact on the quality of life of patients and their families (2, 3).
In the outcome studies published so far (for review, see refs. 4 and5), the long-term morbidity in JIA patients has been most frequently evaluated in terms of functional disability. Currently, the most widely used tool for assessment of functional status is the Childhood Health Assessment Questionnaire (C-HAQ) (6). However, despite its advantages and widespread use, the C-HAQ has been shown to have specific limitations in research and clinical settings. First, it has been demonstrated to have a ceiling effect, with a tendency for scores to cluster at the normal end of the scale, particularly in patients with fewer joints involved (7, 8). Second, its estimation of physical disability in patients with active disease can be inflated by symptoms of inflammation, particularly joint pain (9, 10). Third, the parent's observation of the child's physical function has been found to be frequently inaccurate, being affected by both the severity of arthritis and the level of pain (11). Finally, the C-HAQ may not capture information on several possible forms of damage that may develop in JIA patients over time, such as micrognathia, height retardation, localized growth disturbances, pubertal delay, or visceral organ failure.
Damage in the joints of patients with JIA is assessed by radiographs, which may show the destruction of bone and cartilage. Despite the usefulness of radiographs in studying disease progression, there are some drawbacks. First, radiographs do not fully reflect the biologic outcome of the disease, because they represent mainly cartilage and osseous changes, whereas part of the articular damage in JIA is in the soft tissues surrounding the bones. In addition, radiographs do not measure damage in extraarticular systems or visceral organs. Second, the few available methods for scoring radiographic damage in JIA patients concentrate on the wrists or knees (12–14), whereas damage in other joints may be of equal importance for a patient's functional ability. Third, the cost of measuring radiographic damage and the related radiation exposure make these methods less suitable for studying large numbers of patients or for use in developing countries.
To monitor the course of the disease effectively and to address multiple outcomes over the long term, there is a need for an adjunctive clinical instrument that encompasses all forms of damage that may accumulate in patients with JIA over time. Several attempts to design a method of scoring clinical damage in adult rheumatoid arthritis have been reported (15–18), but such a measure does not exist for JIA. In order to provide a clinical measure that reflects the overall biologic outcome of JIA, we have devised a simple and easy-to-apply clinical index, the Juvenile Arthritis Damage Index (JADI), to assess the total amount of articular and extraarticular damage. In this report, we provide evidence of the reliability and validity of this scale in a large cohort of JIA patients with longstanding disease.
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- PATIENTS AND METHODS
- Appenxix A:
- Appenxix B:
We have described the development of a new clinical measure of articular and extraarticular damage in patients with JIA. It is simple, easy to use, and is quick, taking only 5–15 minutes to score, which makes it practical for use in the clinical setting. The instrument was found to be feasible and to possess both face and content validity; furthermore, it exhibited good convergent construct validity, excellent reliability (interrater agreement and internal consistency), and strong discriminative validity in a large cohort of JIA patients with longstanding disease. The lower performance of the JADI-E as compared with the JADI-A in terms of construct validity and internal consistency was expected, because the former scale addresses a heterogeneous set of organ systems. By documenting these key measurement properties, we have shown that the JADI is a valid instrument for the assessment of accumulated damage in this patient population and is, therefore, potentially applicable in both clinical and research contexts.
The articular component of the JADI has been designed to assess 3 main forms of joint damage that are persistent for at least 6 months and are not due to currently active arthritis: limited ROM, deformity, and previous surgical interventions such as prosthetic replacement, arthrodesis, arthroplasty, or fusion. Although all main joints of the body are assessed, the scale does not require the measurement of all individual joint angles by a goniometer; this would be quite tedious and time-consuming. Instead, for each joint, only the movements that are known to be affected more frequently and precociously in JIA patients (being, thus, a surrogate measure of whole-joint movements) have been included. On the basis of current knowledge of a joint's normal ROM, an experienced examiner may visually estimate, for most joints, whether the ROM is normal or limited by the threshold indicated in the JADI-A. In some joints, particularly the cervical spine, shoulder, and hip, it may be difficult to distinguish damage from reversible impairment due to inflammation. In the case of impairment of shoulder or hip movement, the examiner has to decide whether it is fixed impairment or one that might improve after a corticosteroid injection. In the case of uncertainty, a second assessment (i.e., after 6–12 months) will help to clarify the issue.
Like its articular counterpart, the JADI-E is designed to assess the sources of extraarticular damage most frequently observed in JIA patients. The list of damage items is not intended to be exhaustive, but may be modified or enlarged after the application of the index to other populations of patients seen in different clinical or research settings. In general, we anticipate that both components of the JADI may undergo a process of refinement as we and other investigators incorporate new data, including information on the score change over time. Furthermore, it might be worth investigating whether weighting the JADI-A items differently, depending on the relative importance of each joint to a child's function, would improve the clinical relevance of the overall score. We found that item weighting using a recently developed weighted joint score (34) did not increase the correlations of the JADI-A with the other JIA severity measures (data not shown).
The JADI has been found by us to be a useful and practical tool. This does not mean, however, that it should be the only instrument used for the assessment of long-term outcomes in JIA patients. When we evaluated the Spearman's correlation between the JADI-A and the C-HAQ, we found that the 2 instruments were only moderately correlated. This means that the JADI and the C-HAQ both provide complementary and nonredundant information that facilitates the measurement of long-term morbidity in JIA patients. Notably, the JADI-A and the C-HAQ provided different levels of correlation with the radiographic score and with the HQOL, which are other key measures in JIA outcome studies. The closer relationship of the C-HAQ with the HQOL, particularly with its physical component, is not surprising, because the 2 measures address closely related constructs; likewise, the superior correlation of the JADI-A with the radiographic score was not unexpected, because both are objective measures of joint damage. Taken together, these findings lead us to recommend that both the JADI and the C-HAQ be incorporated, together with a radiographic score, an HQOL tool, and the traditional indicators of disease activity and severity, in a core set of measures that should be used in every longitudinal observational study in JIA. This would provide a framework to investigate the full range of factors that can promote long-term morbidity and disability in JIA.
Some limitations to this study need mentioning. The validation analysis was cross-sectional and therefore issues of causality, predictive validity over time, and responsiveness to clinically meaningful change remain to be examined. Although the index was designed to be sufficiently comprehensive to cover all JIA subtypes, it may not detect all possible forms of damage in the juvenile spondylarthropathies. Notably, the study sample was composed of consecutive patients who continued to receive care at a tertiary pediatric rheumatology care facility at 5 years after disease onset, leading to a potential overrepresentation of patients with more active disease. However, although many of the patients whose disease entered remission in more recent years were probably discharged, the 21-month time frame for study enrollment led us to include most of the patients with mild disease who attended the study units for their annual review.
Therefore, although our study was not designed as an outcome survey, and thus does not reflect outcomes in JIA patients in general, it provides useful information on the disease status of a large population of JIA patients with longstanding disease who are likely to have benefited from the recent advances in the treatment of the disease, such as the widespread use of methotrexate and intraarticular corticosteroids, the aggressive early introduction of these drugs and/or other disease-modifying antirheumatic medications, and, in recent years, the availability of the newer biologic agents. Our finding that only ∼1% of the patients had severe disability confirms the tendency toward a marked improvement in functional outcome seen in recent studies (4, 5, 35). Nonetheless, the degree of impaired function and irreversible damage observed is still considerable and needs to be improved.
In summary, we have developed a new instrument for the assessment of damage to joints and other organs in patients with JIA that we believe is feasible for measuring long-term outcome in large cohorts and for comparing the long-term effectiveness of diverse treatment strategies in different centers and in different countries. This measure is likely to increase current understanding of the natural history of the disease.