A comparison of spinal quantitative computed tomography with dual energy X-ray absorptiometry in European women with vertebral and nonvertebral fractures

Quantitative computed tomography (QCT) was compared to dual X-ray absorptio metry (DXA) measured in the lumbar spine of 508 European women defined as n ormal without fracture (NoF), or osteoporotic (OP), with either vertebral f racture (VF), or peripheral fracture (PF). The correlations between QCT and DXA BMD measurements were significantly different in normal and in osteopo rotic patients, indicating that the two exams do not measure the same bone aspects. According to ROC curves results. QCT Z-sL ores separate OP from No F with better sensitivity than all other measurements. A threshold to diffe rentiate OP from NoF was chosen at Z-score = -1 for DXA-BMD and -1.5 for QC T-BMD. VF patients showed a highly significant decrease in BMD by DXA or QC T. PF patients revealed measurements lower than those of normal subjects bu t greater than those of VF, calling into question the idea of a diffuse ost eoporosis causing nonvertebral fractures that is measurable by spinal DXA o r QCT. DXA is weakly dependent upon age, and T-score or Z-score are equival ent for evaluating osteoporosis. QCT depends greatly upon age. and Z-score appears to be more efficient.