Fibrin D-dimer as a marker of disease activity in systemic onset juvenile rheumatoid arthritis.

OBJECTIVE: To study the prevalence of coagulation abnormalities in children with systemic juvenile rheumatoid arthritis (JRA) using a sensitive marker of fibrin degradation, and to determine whether serial levels of this variable parallel disease activity or predict response to medications in this disease.

METHODS: Levels of d-dimer were determined in 24 consecutive patients with systemic JRA in conjunction with complete blood counts, erythrocyte sedimentation rate, maximum fever, duration of morning stiffness, and swollen joint count. Serial levels were then obtained in 11 patients. Linear regression analyses were done to determine any correlations between d-dimer and the other variables; and paired t test was used to compare levels before and after treatment interventions. Levels of d-dimer were also compared against concurrent clinical events such as pericarditis.

RESULTS: Elevated levels of d-dimer were found in 23/24 of the patients (96%). When serial levels were analyzed, there were correlations between levels of d-dimer and fever (p = 0.03) and total leukocyte count (p = 0.04), but not with other variables. There was a significant reduction in levels before and after treatment in patients deemed to be clinical responders to immunomodulatory agents (p = 0.02). Elevated levels were also indicative of severe disease over the remainder of followup; lack of d-dimer indicated a benign disease course.

CONCLUSION: With the use of a sensitive and specific marker of fibrinolysis known as d-dimer, coagulation abnormalities were more prevalent in children with systemic JRA than previously reported, and are frequently found during periods of active disease. Furthermore, serial levels of d-dimer appear to parallel response to disease modifying agents, and may predict outcome over a short followup period. Fibrin d-dimer may represent a novel marker that, when used in combination with known variables, could enhance that assessment of disease activity and response to medications in children with systemic onset JRA.