Category: Clinical Studies and Observations

8 - Bone Age Assessment by Dual Energy X-ray Absorptiometry

Background: Bone age assessments are generally done using radiography of the hand and wrist to compare the child's maturity to known standards. While a valuable study,the study is not very reflective of short term change. DXA is proposed as able to more precisely reflect both absolute assessments and short term changes in maturation. The current study compares radiographic with Norland bone age assessments to compare studies and sensitivity to change in boys and girls.

Eighteen males subjects (12 to 19 years old) and twenty female subjects (12 to 16 years old) underwent radiographic (GE Discovery XR656 Digital Radiography System) and DXA (Norland XR-800) based bone age assessments to assess agreement between methods. To assess sensitivity to change in the DXA based study, 34 males (6-19 years old) and 37 females (6-16 years old) underwent two DXA-based bone age assessments with three months between studies to assess if a significant increase had occurred in bone mineral. Agreement in age assessment by radiographic and DXA-based bone age study was by regression analysis while assessment of sensitivity to a three-month change in DXA-based assessments was established if follow-up results showed an increase greater than the least significant change limit--4.2% for studies with a 1.2% precision.

X-ray and DXA assessed bone age were found to be highly correlated in males (DXA Bone Age = 14.5777 + 0.9287x; r = 0.9897; P < 0.001) and females (DXA Bone Age = 41.2652 + 0.7619x; r = 0.9250; p < 0.001) suggesting that the two studies are showing similar gross response to bone age. Seventeen of the 34 male subjects showed increases greater than the 4.2% Least Significant Change Limit--the remaining 17 subjects showed differences under 4.2% for the two studies. Examining 34 female subjects, 15 subjects showed increases greater than the 4.2% Least Significant Change Limit--the remaining 19 subjects showed differences below 4.2% in the two studies.

The study demonstrates that the Norland DXA system fitted with Bone Age Assessment Software reflects bone age similarly to that achieved by radiography and can identify significant change in the carpal bones of children in periods as short as three months. We conclude that Bone Age Assessment Software can be useful for bone age assessment and can complement traditional radiographic studies when assessment of short-term change in bone age is desired.

Tom V. Sanchez

Chief Science Officer
Norland at Swissray
Socorro, New Mexico

Jingmei Wang

Director of Densitometry Research
Norland at Swissray
Beijing, Beijing, China (People's Republic)

Yun Sun

Assistant Professor
Hospital of Tsinghua University
Beijing, Beijing, China (People's Republic)