Comparative assessment of bone mineral measurements using dual x-ray absorptiometry and peripheral quantitative computed tomography

A measurement of bone mass is the single most important determinant of futu re fracture. However, controversy exists as to which technique (dual X-ray absorptiometry (DXA) or peripheral quanitative computed tomography (pQCT)), and which site of skeletal measurement (axial vs appendicular) provides th e best prediction of fracture risk. The aims of this study were: (1) to det ermine the ability of pQCT to predict bent: mass of the lumbar spine, proxi mal femur, and distal forearm measured using DXA, and (2) to compare the ab ility of DXA and pQCT to discriminate prevalent fractures in women with est ablished osteoporosis. One hundred and sixty-five women were studied, inclu ding 47 with established osteoporosis (vertebral, hip or Colles' fractures) as well as 118 who had bone mass measurements to assess osteoporosis risk. Each subject had bone mass measured by DXA at the lumbar spine and femoral neck, and at the distal radius by both DXA and pQCT. In women with fractur es, bone mass, when expressed as a standardized score, was in general lower using DXA compared with the appendicular skeleton measured using pQCT. Bon e mass determinations at all sites were significantly correlated with each other. The highest correlation coefficients were observed within the axial skeleton. In women with fractures, the highest odds ratios were observed at skeletal regions measured using DXA. Likewise, the areas under the receive r-operating characteristic (ROC) curves were comparable at all skeletal reg ions measured using DXA; and were significantly greater than the areas unde r the ROC curves for pQCT measurements. In summary, the strongest discrimin ators of prevalent fractures were measurements using DXA. Measurements of b one mass at the appendicular skeleton, using either DXA or pQCT, were poorl y associated with axial bone mass. PQCT has the poorer ability to discrimin ate persons with fractures, and appears to be less sensitive than measureme nts using DXA.