pDXA

Pediatric dual-energy X-ray absorptiometry, abbreviated pDXA, is a imaging modality and analytical method used to measure bone mineral density and body composition in children and adolescents. It uses two X-ray energy levels to differentiate bone, lean tissue, and fat, yielding quantitative data on bone mineral density (BMD), bone mineral content (BMC), and, in many systems, body fat and lean mass.

Scanning typically focuses on sites such as the lumbar spine and the whole body (often excluding the head). In pediatric practice, pDXA reports are presented as areal BMD in g/cm^2 and BMC in grams. Interpretation relies on age- and sex-specific reference data, with pediatric guidelines emphasizing z-scores rather than adult T-scores. Because body size changes with growth, height-for-age and pubertal status are considered, and sometimes height-adjusted or bone mineral density-for-height z-scores are used to improve interpretation.

Normative data for pDXA are device- and software-specific, which may necessitate cross-device calibration when comparing results across instruments. The International Society for Clinical Densitometry (ISCD) provides guidelines for pediatric interpretation, reporting, and quality control to promote standardization of protocols and reference ranges.

Applications of pDXA include assessment of bone health in children with chronic illnesses or treatments that affect bone metabolism (for example, prolonged glucocorticoid exposure, inflammatory diseases, or renal or endocrine disorders) and monitoring responses to therapy. It is also used in research and clinical practice to evaluate body composition in pediatric obesity and growth studies.

Limitations of pDXA include variability related to growth and maturation, device differences, and the need for appropriate pediatric reference data. Radiation exposure is low but a consideration, particularly in longitudinal or repeated measurements.

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