Objective: To evaluate the sensitivity to change of a newly developed radiologic assessment tool, the Dijkstra score, and to develop a numeric composite score and progressor classification scheme to apply in juvenile idiopathic arthritis (JIA) trials.
Methods: A placebo-controlled trial of sulfasalazine (SSZ) in patients with oligoarticular- and polyarticular-onset JIA yielded the data for this study. Data were obtained from 418 sets of radiographs of the clinically involved and contralateral joints (at study entry and at 6 months' followup) from 66 JIA patients. The Dijkstra score assesses the presence or absence of swelling, osteopenia, joint space narrowing, growth abnormalities, subchondral bone cysts, erosions, and malalignment. These signs were combined in the Dijkstra composite score, to assess inflammation (DI), growth (DG), and damage (DD). Progression was defined as an increase in either the DG or the DD score. Scores were evaluated among all radiographs, a standard set of films (hand, foot, and knee), and per patient. All scores were used to explore differences between the 2 treatment groups.
Results: Over time, 58% of joints remained normal, 23% remained abnormal but stable, 14% showed an increase in signs, and 5% showed a decrease in signs. Of the 66 JIA patients, 12% had normal radiographic findings throughout followup, 27% showed abnormalities at some sites without change, and 61% showed change in at least 1 site. Changes in the DI, DG, and DD scores varied considerably per type of joint and occurred most frequently in joints of the standard set. DI and DG scores changed most often in the knees, while DD scores changed primarily in the hands and feet. The disease course in 8% of joints was classified as progressive. Films of SSZ-treated patients, versus the placebo group, showed less deterioration by the DD scores (P = 0.04), and the disease course was more often classified as nonprogressive in the SSZ group (P = 0.037). When progressors were defined as those who had at least one radiograph showing progression, significantly more placebo-treated patients were considered progressors (P = 0.046).
Conclusion: In this trial data set, the Dijkstra composite score and the resulting progressor classification system are comprehensive and feasible tools that are sensitive to change and discriminate between clinical situations. They should now be tested by other investigators and in other data sets.