To determine cutoff values for defining remission, minimal disease activity, and parent and child acceptable symptom state in juvenile idiopathic arthritis (JIA) using the Juvenile Arthritis Disease Activity Score (JADAS).
For the selection of cutoff values, data from a clinical database including 609 children with JIA were used. Optimal cutoff values were determined against external criteria by calculating the 75th percentile of cumulative score distribution and through receiver operating characteristic curve analysis. External criteria included formal definitions of inactive disease and minimal disease activity, subjective rating of remission by physicians, parents, and children, and rating of acceptable symptom state by parents and children. The choice of cutoffs was made based on clinical and statistical grounds. Cross-validation was performed using 4 JIA patient samples that included a total of 1,323 patients, and was based on assessment of construct, discriminant, and predictive validity.
With all versions of the JADAS, the cutoff score for classifying a patient as having inactive disease was 1, whereas the cutoff for classification of minimal disease activity was 2 for oligoarticular JIA and 3.8 for polyarticular JIA. Cutoffs for physicians', parents', and children's subjective rating of remission ranged from 2 to 2.3. Cutoffs for acceptable symptom state ranged from 3.2 to 5.4 for parents and from 3 to 4.5 for children. Results of cross-validation analyses strongly supported the selected cutoff values.
Cutoff values for classifying various disease states in JIA using the JADAS were developed. In cross-validation analyses, they proved to have good construct and discriminant validity and ability to predict disease outcome.