Comparison of rates of change in bone density as measured by dual-energy X-ray absorptiometry and quantitative computed tomography in osteoporotic females treated with fluoride

We conducted a retrospective comparison of the rates of change in vertebral bone density measured by two densitometric techniques: dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) in osteoporotic women treated with fluoride. To compare both densitometric methods, lumbar vertebral bone density was determined before and during fluoride therapy in 104 osteoporotic women. All patients signed an informed consent under a protocol approved by our University Institutional Review Board. All subjects had at least three serial measurements using both densitometric techniques over the studied time period. Linear regression was used to calculate rate of change values for each patient. In agreement with previous published reports, lumbar density increased linearly over time both with DXA and QCT. Rates of change determined by DXA and QCT were significantly correlated (r = 0.88, p < 0.0001) and this relationship was independent of the magnitude of the increase in density. Either densitometric technique may be used to evaluate the axial skeletal response to fluoride therapy.