Study data published in Rheumatology support the validity of a new composite disease activity score for systemic juvenile idiopathic arthritis (sJIA). Developed and validated by a team of pediatric rheumatologists, the systemic Juvenile Arthritis Disease Activity Score (sJADAS) showed high internal consistency and was able to distinguish between patients in different disease activity states. The sJADAS also appropriately captured changes in symptoms over time.
The sJADAS was constructed by adding a fifth item to the existing 4-item JADAS. The fifth item sought to quantify the systemic effects of disease using a modified version of the Systemic Manifestation Score (SMS). The SMS uses 7 clinical and laboratory features to quantify systemic manifestations of JIA: fever, rash, generalized lymphadenopathy, hepatomegaly and/or splenomegaly, serositis, anemia, and platelet and ferritin levels.
Validation analyses of the 5-item sJADAS were conducted in patients with definite or probable/possible sJIA from 30 pediatric rheumatology centers in 10 countries. Patients with sJIA without systemic manifestations were excluded from the study. At study entry, patients underwent clinical assessment and evaluation with the sJADAS. Patients were re-assessed at a second visit 2 weeks to 3 months after the initial visit. Three versions of the sJADAS were tested: (1) a version including erythrocyte sedimentation rate (ESR); (2) a version including C-reactive protein (CRP); and (3) a version lacking acute-phase reactants (APR).
The study cohort comprised 163 patients with sJIA. All 3 composite versions of the sJADAS showed high correlation with other measures of disease activity, including parent-reported pain assessment, physical function score, and health-related quality of life (Spearmen’s correlation coefficient, 0.41-0.60). The sJADAS version using ESR (sJADAS10-ESR) tended to display better correlation with other measures than the sJADAS versions using CRP or APR.
Internal consistency was satisfactory for the sJADAS (Cronbach’s alpha, 0.64-0.65). The sJADAS showed strong ability to discriminate between disease activity states as determined by the treating physician (P <.0001). Similarly, the sJADAS was able to distinguish between patients whose parents were satisfied with illness outcome and patients whose parents were not (P <.0001). The sJADAS was found to respond to symptom change between baseline and follow-up. The standardized response means ranged from 2.04 to 2.58 across the 3 proposed versions of the sJADAS. Responsiveness to change was higher with the sJADAS than with some existing measures of sJIA activity, including the original JADAS (2.06-2.17), the clinical JADAS (1.81-1.89), and composite scores using adult disease measures (1.39-1.86).
These data support the feasibility and validity of an updated disease activity score measuring manifestations of sJIA. However, these results represent only preliminary evidence for the utility of the sJADAS. “The performance of the new tool should be further examined in other patient cohorts that are evaluated prospectively,” the investigators wrote.
Tibaldi J, Pistorio A, Aldera E, et al. Development and initial validation of a composite disease activity score for systemic juvenile idiopathic arthritis. Rheumatology (Oxford). Published online August 23, 2020. doi:10.1093/rheumatology/keaa240