Use of quantitative ultrasound to assess bone status in children with juvenile idiopathic arthritis

Periarticular osteoporosis around inflamed joints and generalized osteoporo sis have been shown to be markers of disease activity and severity in child ren with juvenile idiopathic arthritis (JIA). Bone mineral density (BMD) il l adults can be assessed precisely by dual X-ray absorptiometry (DXA), but this technique has not been used widely in children. Quantitative ultrasoun d (QUS) may provide an alternative method for assessment of bone status. Th e aim of this pilot study was to compare QUS to DXA in assessing generalize d osteoporosis in a cohort of patients with JIA. Twenty-two Caucasian child ren (15 females, 7 males) with JIA of duration of 19-142 (mean 71 mo) and a ge 7-17 yr were recruited. Total body and lumbar spine BMD and bone mineral content (BMC) were measured by DXA using standard procedures on a Lunar DP X-L scanner. QUS was performed using Myriad SoundScan 2000. Speed of sound sound (SOS) was measured at the right midtibia. The DXA results were compar ed to QUS using linear regression analysis. Spine and total body BMD measur ed by DXA correlated significantly with tibia SOS (spine: r = 0.57, p < 0.0 07; total body: r = 0.68, p < 0.001). Spine BMC was similarly related to SO S as BMD (I = 0.58, p < 0.007). Individual patient weight and height were s trong predictors of BMD, but only moderate predictors of SOS. The mean spin e BMD was lower in the JIA patients compared to the normal ranges (mean Z-s core of -1.19). BMD Z-scores were negatively associated with duration of di sease. patients taking steroids were associated with lower Z-scores. In con clusion, SOS shows a significant correlation with BMD as measured by DXA, a lbeit with wide 95% confidence intervals in this small pilot study. QUS was also well tolerated and was technically easy to perform in these children. With the added advantage that it is free from radiation risk, further asse ssment of this potentially valuable tool for measuring bone status in child ren is warranted.