Candidate Early Predictors for Progression to Joint Damage in Systemic Juvenile Idiopathic Arthritis
CHRISTY SANDBORG, TYSON H. HOLMES, TZIELAN LEE, KATHLEEN BIEDERMAN, DANIEL A. BLOCH, HELEN EMERY, DEBORAH McCURDY, and ELIZABETH D. MELLINS
Objective. To assess if joint damage at 2 years after diagnosis in patients with systemic juvenile idiopathic arthritis (SJIA) can be predicted by clinical or laboratory features assessed up to 3 or 6 months after diagnosis.
Methods. Medical records from 70 children were retrospectively reviewed. The primary outcome measure was presence of joint damage at 2 years after diagnosis (JD2) as defined by presence of erosions or fusion in one or more joints. Potential predictor variables for JD2 in the first 3 and 6 months after diagnosis consisted of the highest observed white blood cell count, platelet count, erythrocyte sedimentation rate, active joint count, and presence of symptomatic pulmonary or cardiac disease or macrophage activation syndrome, and treatment data.
Results. The outcome of interest, JD2, was identified in 15/70 patients. Classification-tree analysis identified a pair of variables (highest observed platelet count and number of active joints) measured within the first 3 months after diagnosis that together predicted progression to JD2 with an estimated sensitivity of 87%, specificity of 82%, and positive predictive value of 57%. Multivariate logistic regression analyses at 3 months found that higher quantities of joints with active arthritis and early use of methotrexate (MTX) were factors significantly associated with increased odds of progression to JD2 (active joints odds ratio = 1.08, 95% CI 1.00–1.16, p = 0.04; MTX OR = 11.85, 95% CI 1.89–74.26, p = 0.01). Unsupervised cluster analysis identified 2 major phenotypes of patients at 3 months characterized by different ages at onset, acute phase markers, active joint counts, and presence of serositis. These phenotypes differed 3-fold in proportion of subjects progressing to JD2 (p < 0.05).
Conclusion. By 3 months after diagnosis, a clinical phenotype based on active joint count and platelet count may be prognostic of an increased risk of progression to JD2. Use of corticosteroids did not appear to change the risk of joint damage. In contrast, the presence of serositis appeared to be associated with decreased risk of joint damage. (First Release Sept 1 2006; J Rheumatol 2006;33:2322-9)
Key Indexing Terms:
SYSTEMIC JUVENILE ARTHRITIS
From the Department of Pediatrics and Department of Health Research and Policy (Biostatistics), Stanford University School of Medicine, Stanford, California; Department of Pediatrics, University of Washington Medical School, Seattle, Washington; and Department of Pediatrics, UCLA School of Medicine, Los Angeles, California, USA.
Supported by grants from the Arthritis Foundation, The Wasie Foundation, Lucile Packard Foundation for Children's Health, Oxnard Foundation, and Valley Foundation.
C.I. Sandborg, MD, Department of Pediatrics; T.H. Holmes, PhD, Department of Health Research and Policy (Biostatistics); T. Lee, MD, Department of Pediatrics; K. Biederman, RN, Department of Pediatrics; D.A. Bloch, PhD, Department of Health Research and Policy (Biostatistics), Stanford University School of Medicine; H. Emery, MD, Department of Pediatrics, University of Washington Medical School; D. McCurdy, MD, Department of Pediatrics, UCLA School of Medicine; E. Mellins, MD, Department of Pediatrics, Stanford University School of Medicine.
Address reprint requests to Dr. C. Sandborg, Department of Pediatrics, Room G310, Stanford University Medical Center, 300 Pasteur Drive, Stanford CA 94305-5208. E-mail: Sandborg@stanford.edu
Accepted for publication June 1, 2006.