Regional versus total body bone mass and body composition during infancy

Abstract

Summary Background & aims Total body dual energy X-ray absorptiometry (DXA) is a useful non-invasive technique in the assessment for bone and soft tissue growth and development in infants although the role of regional DXA measurements is not well defined. Methods Regional measurements including extremities, trunk and head were obtained by software delineation from a database of infant whole body DXA scans based on pencil beam (PB) and fan beam (FB) DXA techniques. Results Data from fan beam or pencil beam were similar. All regional DXA measurements were correlated and predictive of total body measurements. The relationship to total body measurements was better for larger regions such as the trunk and lower extremities, and for lean, fat, bone mineral content, fat and fat percent (adjusted r 2 0.78 to 0.98 for FB and 0.82 to 1.00 for PB). At the head region, bone mineral density was best related to total body measurements with adjusted r 2 > 0.92 for both DXA techniques. DXA measurements from left and right extremities were correlated but the agreement varied among different DXA parameters. Weight was the best predictor for regional as well as total body bone and soft tissue measurements although other physiologic predictors including length, age, gender and race could be forced into prediction equation. Conclusions Regional DXA measurements may be considered as a screening tool to monitor changes in bone and soft tissue composition during infancy but they should not be used as a surrogate replacing total body measurements.