Z score prediction model for assessment of bone mineral content in pediatric diseases

The objective of this study was to develop an anthropometry-based predictio n model for the assessment of bone mineral content (BMC) in, children. Dual -energy X-ray absorptiometry (DXA) was used to measure whole-body BMC in a heterogeneous cohort of 982 healthy children, aged 5-18 years, from three e thnic groups (407 European- American [EA], 285 black, and 290 Mexican-Ameri can [MA]). The best model was based on log transformations of BMC and heigh t, adjusted for age, gender, and ethnicity. The mean +/- SD for the measure d/predicted In ratio was 1.000 +/- 0.017 for the calibration population. Th e model was verified in a second independent group of 588 healthy children (measured/predicted In ratio = 1.000 +/- 0.018). For clinical use, the rati o values were converted to a standardized Z score scale. The whole-body BMC status of 106 children with various diseases (42 cystic fibrosis [CF], 29 juvenile dermatomyositis [JDM], 15 liver disease [LD], 6 Rett syndrome [RSI , and 14 human immunodeficiency virus [HIV]) was evaluated. Thirty-nine pat ients had Z scores less than -1.5, which suggest low bone mineral mass. Fur thermore, 22 of these patients had severe abnormalities as indicated by Z s cores less than -2.5. These preliminary findings indicate that the predicti on model should prove useful in determining potential bone mineral deficits in individual pediatric patients.