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

Abstract

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). Case-control study included 93 children on maintenance HD (9-18years; 48 males). Participants were subjected to spinal-DXA-scan to obtain areal bone mineral density (aBMD; g/cm2). Volumetric-BMD (vBMD; g/cm3) was mathematically estimated. Z-scores of aBMD for chronological age (aBMDZ-CA), aBMD adjusted for height age (aBMDZ-HA), and vBMDZ-score were calculated using mean and SD values of age subgroups of 442 healthy controls (7-18years). In short-for-age CKD patients, aBMDZ-CA was significantly lower than vBMDZ-score, while aBMDZ-HA was significantly higher than aBMDZ-CA and vBMDZ-score. In normal height-for-age CKD patients, no significant difference between aBMDZ-scores and vBMDZ-score was detected. aBMDZ-CA was significantly lower and aBMDZ-HA was significantly higher in short-for-age compared to normal height-for-age patients without significant differences in vBMDZ-score. We observed age-related decrements in the percentage of HD patients with normal densitometric Z-scores, the effect of age was less pronounced in aBMDZ-HA than vBMDZ-score. vBMDZ-score correlated negatively with age, but not with heightZ-score. 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. aBMDZ-CA underestimates, while aBMDZ-HA overestimates BMD in such patients.