Interpreting a DXA Scan in Clinical Practice

Osteoporosis is a metabolic bone disorder characterized by low bone mass and microarchitectural deterioration, with a subsequent increase in bone fragility and susceptibility to fracture. Dual-energy x-ray absorptiometry (DXA) is recognized as the reference method to measure bone mineral density (BMD) with acceptable accuracy errors and good precision and reproducibility(Blake and Fogelman 2007). The World Health Organization (WHO) has established DXA as the best densitometric technique for assessing BMD in postmenopausal women and based the definitions of osteopenia and osteoporosis on its results (table 1)(Kanis 1994; Kanis, Borgstrom et al. 2005). DXA allows accurate diagnosis of osteoporosis, estimation of fracture risk, and monitoring of patients undergoing treatment. Additional features of DXA include measurement of BMD at multiple skeletal sites, safety of performance, short investigation time, and ease of use(Hans, Downs et al. 2006; Lewiecki, Binkley et al. 2006). A DXA measurement can be completed in about 5 minutes with minimal radiation exposure (about one tenth that of a standard chest x-ray for a quick hips and spine exam).