SPINAL BONE-MINERAL ASSESSMENT IN POSTMENOPAUSAL WOMEN - A COMPARISONBETWEEN DUAL X-RAY ABSORPTIOMETRY AND QUANTITATIVE COMPUTED-TOMOGRAPHY

We compared quantitative computed tomography (QCT) and dual X-ray abso rptiometry (DXA) with respect to their ability to discriminate subject s with and without prevalent vertebral fractures. In 240 post-menopaus al women (mean age 63.7 +/- 6.9 years) lateral spine radiographs (T4-L 4) were reviewed for the presence of vertebral fracture. Using a semiq uantitative technique to grade the severity of vertebral deformities, we classified fractures as mild, moderate or severe (grade 1 to 3, res pectively). Postero-anterior DXA (PA-DXA) and lateral DXA (L-DXA) meas urements (L2-4) as well as QCT measurements of the lumbar spine (T12-L 3 or L1-14) were obtained in all women. Seventy-two women were diagnos ed with at least one fracture, and of these 40 were graded as mild. Co mparing normal women with fractured women, we found the area under the receiver operating characteristics (ROC) curves to be greatest for QC T (0.81), followed by L-DXA (0.72) and PA-DXA (0.65). The differences among all three techniques were significant. Comparing the normal wome n with women having only mild fractures, the areas under the ROC curve s were 0.79, 0.73 and 0.63 for QCT, L-DXA. and PA-DXA, respectively. S ignificant differences existed between QCT and PA-DXA as well as betwe en L-DXA and PA-DXA. Logistic regression analysis also revealed the hi ghest age-adjusted odds ratios for QCT (3.67; 2.25-5.97) while L-DXA a nd PA-DXA showed substantially lower odds ratios (2.00; 1.39-2.87, and 1.54; 1.11-2.15, respectively). We conclude that low bone density as measured by QCT, PA-DXA or L-DXA is significantly associated with the prevalence of vertebral fractures. Of the methods studied, QCT of trab ecular bone offered the best discriminatory capability. L-DXA proved t o be superior to PA-DXA in its diagnostic sensitivity, particularly in women with mild fracture. Mild vertebral fractures are associated wit h decreased spinal bone density and may be regarded as osteoporotic de formities.