Association between bone indices assessed by DXA, HR-pQCT and QCT scans in post-menopausal women

Quantitative computed tomography (QCT), high-resolution peripheral QCT (HR-pQCT) and dual X-ray absorptiometry (DXA) scans are commonly used when assessing bone mass and structure in patients with osteoporosis. Depending on the imaging technique and measuring site, different information on bone quality is obtained. How well these techniques correlate when assessing central as well as distal skeletal sites has not been carefully assessed to date. One hundred and twenty-five post-menopausal women aged 56-82 (mean 63) years were studied using DXA scans (spine, hip, whole body and forearm), including trabecular bone score (TBS), QCT scans (spine and hip) and HR-pQCT scans (distal radius and tibia). Central site measurements of areal bone mineral density (aBMD) by DXA and volumetric BMD (vBMD) by QCT correlated significantly at the hip (r = 0.74, p < 0.01). Distal site measurements of density at the radius as assessed by DXA and HR-pQCT were also associated (r = 0.74, p < 0.01). Correlations between distal and central site measurements of the hip and of the tibia and radius showed weak to moderate correlation between vBMD by HR-pQCT and QCT (r = -0.27 to 0.54). TBS correlated with QCT at the lumbar spine (r = 0.35) and to trabecular indices of HR-pQCT at the radius and tibia (r = -0.16 to 0.31, p < 0.01). There was moderate to strong agreement between measuring techniques when assessing the same skeletal site. However, when assessing correlations between central and distal sites, the associations were only weak to moderate. Our data suggest that the various techniques measure different characteristics of the bone, and may therefore be used in addition to rather than as a replacment for imaging in clinical practice.