Dual energy X-ray absorptiometry (DEXA) measurements of bone density and body composition: promise and pitfalls.

Dual energy X-ray absorptiometry (DEXA) is widely viewed as the preferred method to assess pediatric bone mineral content because of its speed, precision, and minimal radiation exposure, and the availability of pediatric reference data. DEXA can also be used to estimate body composition precisely with minimal patient cooperation. Accurate interpretation of DEXA data in children requires consideration of bone size, pubertal stage, skeletal maturation, ethnicity and body composition. Bone mineral content may be underestimated in smaller children and overestimated in larger ones. Corrections for skeletal age or sexual maturity may also be needed in children with advanced or delayed growth. Errors in body composition measurement occur because body fat and fat-free mass are not distributed uniformly. In addition, fat mass present adjacent to bone will influence the measurement of bone mineral content. In conclusion, DEXA is a valuable tool for assessing pediatric bone health, but accurate interpretation of densitometry results requires recognition of a myriad of pitfalls.