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- PATIENTS AND METHODS
In this 17-year followup study, the majority of patients with JIA had a favorable outcome, even though changes in body function and structure were observed in more than half of the adolescents and adults at followup. However, the observed changes were often very mild and did not always result in functional limitation or a perceived burden of illness. Key outcome features such as mortality or amyloidosis turned out to be not as relevant as they were years ago (29, 30), with a mortality rate of 0% (or at least <1.5%) and an amyloidosis rate of 1.4%. The same applies to severe extraarticular organ damage, which was experienced by 1.4% of patients, 2 of whom lost their eyesight because of uveitis.
In this JIA cohort, ocular involvement was the most common extraarticular manifestation and was observed in 14% of patients, which is comparable with findings of recent studies on uveitis in juvenile arthritis (31, 32). Uveitis was most often experienced by patients with ERA, predominantly as symptomatic uveitis, and no patient in the group with psoriatic arthritis had uveitis. This may be attributable to the small number of patients fulfilling the ILAR inclusion criteria for psoriatic arthritis. Otherwise, uveitis was seen in 4 of the 17 patients who had both arthritis and psoriasis. Half of the patients with uveitis reported having developed sequelae due to uveitis, as manifested by reduced eyesight in 12 patients. The extent of vision loss could not be ascertained, however, because an ophthalmologic examination was not part of the followup assessment.
Other changes in body function and structure included tender/swollen joints (41% of patients), restrictions in joint motion (54%), and local growth disturbances (26%). The prevalence of the latter appeared to be relatively high, with limb length discrepancies representing most of the growth disturbances. The clinical importance of this finding is questionable, however, because the majority of patients had leg length differences of 1 cm or less. Furthermore, because even in the general population, the frequency of leg length inequalities of 1 cm or more is reported to be 23% (33), this finding as a JIA-related outcome parameter must be checked by including a control group.
The relatively high number of joint operations (performed on 45% of all patients) does not reflect joint damage but rather the formerly used therapeutic strategy of “early” synovectomy in order to prevent disease progression. The data are not appropriate for assessing the effect of this procedure on outcome, but they give the impression that synovectomies at least did not prevent the above-mentioned changes, such as residual restrictions in joint motion or limb length discrepancies.
Approximately half of the patients had active disease at followup, usually at a low level. This proportion is in the range of 37–66%, which was reported in previous long-term outcome studies (3, 9). We found that remission rates in the population-based and referral-based cohorts were comparable, leading to the assumption that the remission rates of the whole cohort are representative. Patients with oligoarticular-onset JIA were most often in remission; the remission rate was only 54%, however, probably because of the heterogeneity of this group. Almost half of patients with oligoarthritis had developed polyarticular arthritis or a form of spondylarthropathy (e.g., AS) over the course of their disease, for which remission rates were 12% and 0%, respectively. A comparable rate of subtype change was described by Guillaume et al (10), who reported that among patients with oligoarticular-onset JIA, the probability of a polyarticular course was 50%, and that the remission rate was only 36%. In addition, we found the very low remission rate of 18% for patients with ERA. The high prevalence of current inflammatory back pain, an exclusion criterion for remission, was responsible for this low rate. At followup, 39% of the patients with ERA had definite AS, and 36% had possible AS. These figures are similar to those reported by other investigators (34, 35).
In the present study, 6.5% of patients had an HAQ score of 1.0 or higher, and 10% were severely disabled according to Steinbrocker functional class status; these figures are in accordance with those of other recent studies of JIA outcome (5, 9). Changes in body function and structure (e.g., disease activity and joint abnormalities) correlated with functional limitation at followup. Current disease activity had the strongest influence on functional status, and disease duration was not significantly correlated with the HAQ score. This finding was somewhat unexpected, because other long-term studies have shown that the fraction of disabled patients clearly increased in association with longer time-span to followup (9, 36, 37). The fact that we found only a tendency for a worsening of functional status with increasing disease duration could be attributable to patients' adaptations to their limitations. The patients could have changed their perception of their abilities gradually, so that the HAQ score does not correctly reflect functional loss over time, a fact also stated by Wolfe (38).
Functional status as rated by the physicians also did not worsen over time. This is shown by comparing the Steinbrocker functional classes of patients assessed in both the 7-year and 17-year-followup studies. Therefore, the data suggest that current disease activity, pain, and psychological factors are more relevant than disease duration in terms of patients' functional status at followup.
Because a successful transition from school to work plays a key role in the social integration of adolescents with arthritis, a patient's employment status might best reflect the social consequences of JIA. In this cohort, more than half of the 20–35-year-old patients were employed at followup, but one-fourth of the patients in this age group were still completing vocational training, possibly deferring their transition into the work force. The unemployment rate observed among patients in our study was lower than that in the corresponding age-matched population. This finding contradicts those of other investigators (3, 6), who reported significantly increased unemployment rates in adults with a history of JIA compared with controls, despite similar or even better attainments in formal education. The latter finding was also observed in our study.
Despite the good physical functioning and social integration of the patients in general, many patients, especially those with active disease, felt burdened by their illness and were in need of care. Therefore, the question arises whether more intensive therapy in adulthood might have improved outcome, considering the number of patients receiving NSAIDs (21%) or DMARDs (26%) at followup.
As with any study, our results must be interpreted in light of certain limitations. First, we relied on data from the 2nd Children's Hospital, where only recognized and referred patients were treated. Thus, the possibility that some undetected cases were missed cannot be ruled out. Second, no control group was included, which limits the capacity to make comparisons. Third, 16% of the patients (mainly those with oligoarthritis) were lost to followup, which might have biased the results. Finally, we used one standardized measurement for all patients, which could not consider the specifics of the various JIA subgroups.
In summary, although very severe disease outcomes in JIA are more rare than they were decades ago, JIA-related morbidity in adulthood is still evident. When interpreting these results, it must be kept in mind that the outcome data relate to patients who became ill and were treated 10–30 years ago. Therefore, they received therapy that is somewhat different from that currently provided. Further studies will show if the long-term outcome in JIA patients treated today is, as expected, better than that of patients in this cohort.