Analysis and Evaluation of DXA in Children and Adolescents
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Analysis and evaluation of DXA scans are contingent upon acquisition of high-quality scans, devoid of movement and other artifacts that may affect BMC or aBMD results. Innovations in DXA scan analysis software enable standardized analysis of scans on pediatric patients. Placement of the regions of interest (ROI) according to manufacturer’s guidelines and examination of the “bone map” are important to ensure that the scan is analyzed appropriately. The lateral distal femur scan is less standardized but may be useful for assessing bone density in non-ambulatory patients who are at increased risk of femur fractures. It is recommended that follow-up scans be analyzed using the “compare mode” to optimize the comparability of aBMD results.
The T-score should never be used for children. To account for age-related increases in BMC and aBMD in growing children, age, sex, and race-specific reference values should be used to calculate a Z-score. Selection of reference data should consider (1) the instrument manufacturer and software version as the absolute DXA values acquired on devices of different manufacturers vary, (2) provision of sex and race-specific reference curves, and (3) whether a sufficiently large sample size was used to generate the curves. In children with growth delay, it is important to estimate the effect of size-related artifact on aBMD Z-scores. This may be achieved by use of adjustments that incorporate the child’s height for age Z-score or by use of bone mineral apparent density (BMAD). BMD or BMC Z-scores alone cannot be used to diagnose osteoporosis. Low or very low Z-scores should trigger additional evaluations. Interpretation of DXA scan results should be done within the context of other relevant clinical information. Even children without low Z-scores may be not be achieving their genetic potential for bone mass.
KeywordsEvaluation Scan analysis Reference data Z-scores Size adjustment Osteoporosis
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