Bone Abstracts

Background: Height is required for interpretation of bone mineral density in children and is often challenging in non-weight bearing children. Monitoring of linear growth in non-weight bearing children as part of assessment of bone health is also important.

Objective: To investigate the feasibility of a novel method of using DXA images to measure height (Ht), sitting height (SH) and leg length (LL).

Methods: Ht and SH were measured on DXA digital images performed for clinical monitoring of bone health on three separate occasions in 125 children by one single observer (RM). Twenty five children had Ht and SH measurements performed in clinic on the same day as DXA scans. Intra-class correlation (ICC) was used to assess reliability (three readings). Bland-altman plots were used to evaluate validity of DXA based measurements. Accuracy of DXA Ht SDS, SH SDS and LL SDS was pre-determined as agreement with clinic measurements of within ±0.3 SD.

Results: ICC of DXA Ht and SH were 0.999 (95% CI 0.998 to 0.999), respectively and ICC of DXA LL was 0.997 (95% CI 0.991 to 0.995), indicating almost perfect reliability. Mean difference of DXA Ht SDS with clinic measurements was −0.099, with upper limits of agreement of 0.072 (95% CI 0.058 to 0.082) and lower limits of agreement of −0.270 (95% CI −0.258 to −0.282). Mean difference of DXA SH SDS with clinic measurements was −0.393, with upper limits of agreement of 0.366 (95% CI 0.317 to 0.423) and lower limits of agreement of −1.153 (95% CI −1.097 to −1.203). Mean difference of DXA LL SDS with clinic measurements was −0.207, with upper limit of agreement of 0.938 (95% CI 0.791 to 1.089) and lower limits of agreement of −0.524 (95% CI −0.371 to −0.669).

Conclusion: This study demonstrated for the first time that measuring height, sitting height and leg length using DXA images is feasible and highly reproducible. However, only height measurements showed good agreement with the gold standard of clinic measurements, suggesting that height measurements of non-weight bearing children undergoing DXA scan for monitoring of bone health can be performed.

Disclosure: The authors declared no competing interests.