Is Calcaneal Broadband Ultrasound Attenuation a Valid Index of DXA-derived Bone Mass in Children?

The gold standard of bone mass estimation is radiation-based dual-energy x-ray absorptiometry (DXA) from which bone mineral density (BMD) is derived. Broadband ultrasound attenuation (BUA) by quantitative ultrasonometry (QUS) is a quick, safe and portable alternate measure of bone health, and is therefore commonly utilised in pediatric studies. BUA is not, however a direct measure of bone mass, and therefore its validity as a surrogate measure for BMD is sometimes questioned.

PURPOSE: Our aim was to determine the validity of calcaneal BUA as a surrogate for BMD in pediatric populations. Specifically, we sought to determine the ability of BUA to predict whole body and regional BMD in pre-, peri-, and post-pubertal boys and girls.

METHODS: Three hundred and eighty-nine boys and girls across a wide age range (4 to 18 years) volunteered to participate. Age of peak height velocity was calculated with an algorithm based on height, weight, age and sex in order to classify children into pre-, peri-, and post-pubertal groups. BUA was measured at the non-dominant calcaneus (QUS, Lunar Achilles Insight, GE) while BMD and bone mineral content (BMC) were examined at the femoral neck (FN), lumbar spine (LS) and whole body (WB) (DXA, XR-800, Norland). Linear regression analyses were undertaken to examine the relationships between BUA and DXA-derived bone mass measures.

RESULTS: BUA held significant positive associations with BMC and BMD at whole body and regional sites for boys and girls across all maturational levels. For the whole sample, BUA predicted 29% of the variance in WB BMC and BMD, 23-24% of the variance in LS BMC and BMD, and 21-24% of the variance in FN BMC and BMD (p < 0.001). BUA predictions were strongest for the most mature participants (pre-pubertal R2 = 0.03-0.19; peri-pubertal R2 = 0.05-0.17; post-pubertal R2 = 0.18-0.28) and marginally stronger for girls (R2 = 0.25-0.32, p < 0.001) than boys (R2 = 0.21-0.27, p < 0.001).

CONCLUSIONS: We observed significant relationships between calcaneal BUA and DXA measures of bone mass with strongest associations for children in the post-pubertal group. Our results suggest that calcaneal BUA provides a valid index of bone mass at clinically important sites in children.