Size-adjustment techniques of lumbar spine dual energy X-ray absorptiometry measurements in assessing bone mineralization in children on maintenance hemodialysis.

Objectives: Growing skeleton is uniquely vulnerable to impaired mineralization in chronic kidney disease (CKD). Continued debate exists about the optimal method to adjust for body size when interpreting dual energy X-ray absorptiometry (DXA) scans in children with CKD given the burden of poor growth. The study aimed to evaluate the clinical usefulness of size-adjustment techniques of lumber-spine DXA measurements in assessing bone mineralization in children with kidney failure on maintenance hemodialysis (HD).

Methods: Case-control study included 93 children on maintenance HD (9-18 years; 48 males). Participants were subjected to spinal-DXA-scan to obtain areal bone mineral density (aBMD; g/cm). Volumetric-BMD (vBMD; g/cm) was mathematically estimated. Z-scores of aBMD for chronological age (aBMD), aBMD adjusted for height age (aBMD), and vBMD were calculated using mean and SD values of age subgroups of 442 healthy controls (7-18 years).

Results: In short-for-age CKD patients, aBMD was significantly lower than vBMD, while aBMD was significantly higher than aBMD and vBMD. In normal height-for-age CKD patients, no significant difference between aBMD and vBMD was detected. aBMD was significantly lower and aBMD was significantly higher in short-for-age compared to normal height-for-age patients without significant differences in vBMD. We observed age-related decrements in the percentage of HD patients with normal densitometric Z-scores, the effect of age was less pronounced in aBMD than vBMD. vBMD correlated negatively with age, but not with height.

Conclusions: Estimated vBMD seems to be a convenient size-adjustment approach of spinal-DXA measurements in assessing BMD especially in older short-for-age children with CKD. aBMD underestimates, while aBMD overestimates BMD in such patients.