PREDICTORS OF TOTAL-BODY BONE-MINERAL DENSITY IN NON-CORTICOSTEROID-TREATED PREPUBERTAL CHILDREN WITH JUVENILE RHEUMATOID-ARTHRITIS

Objective, To determine the extent of significant osteopenia in prepub ertal patients with juvenile rheumatoid arthritis (JRA) not treated wi th corticosteroids and to identify variables that are highly related t o bone mineralization in this population. Methods. In a cross-sectiona l study, 48 JRA patients and 25 healthy control subjects ages 4.6-11.0 years were evaluated. Total body bone mineral density (TB BMD) was de termined by Hologic dual energy x-ray absorptiometry. All patients wer e prepubertal (Tanner stage I or II) and had never taken corticosteroi ds. For comparison, JRA patients were divided into ''low'' TB BMD (Z s core less than or equal to -1) or ''normal'' TB BMD (Z score >-1). Res ults. The overall mean +/- SD TB BMD scores did not differ between the JRA subjects (0.75 +/- 0.06 gm/cm(2)) and controls (0.73 +/- 0.07 gm/ cm(2); P > 0.30), However, 29.2% of the JRA patients had low TB BMD, w hereas only 16% would be expected to have low TB BMD based on the stan dard normal distribution (goodness of fit chi(2) = 4.84, P = 0.01), Th e mean Z score for the JRA patients with low TB BMD was -1.43, and for those with normal TB BMD, it was 0.32, The JRA subjects with low TB B MD were significantly younger, had more active articular disease, grea ter physical function limitation, higher erythrocyte sedimentation rat e, higher joint count severity score, lower body mass index, lower lea n body mass, less participation in organized sports, and more protein and vitamin D in their diet compared with JRA patients with normal TB BMD (all P < 0.05), Using logistic regression, a model including age a t JRA onset, Juvenile Arthritis Functional Assessment Report (JAFAR) s core, triceps skinfold percentiles, percentage US recommended daily al lowance for dietary magnesium intake, and serum 1,25-dihydroxyvitamin D levels was able to accurately segregate 79.6% of the JRA subjects in to either the low or normal TB BMD groups (chi(2) = 20.5, P = 0.001). Conclusion. This study demonstrated that in a mildly to moderately ill prepubertal JRA population that had never been exposed to corticoster oids, almost 30% had significantly low TB BMD, The patients with low T B BMD had more active and severe articular disease and greater physica l function limitation, Disease-related parameters in JRA appear to exe rt a negative effect on bone mineralization even in prepubertal childr en, which can be demonstrated despite the exclusion of corticosteroid- treated patients.