A comparison of quantitative computed tomography and dual X-ray absorptiometry for evaluation of bone mineral density in patients on chronic hemodialysis

Abstract

Chronic renal failure leads to a reduction of bone mineral density (BMD). Therefore, noninvasive methods to evaluate BMD are also used regularly in this patient population. In this study, we compared the results of two widely used methods, quantitative computed tomography (QCT) of the lumbar spine and dual x-ray absorptiometry (DXA) at different sites in 90 patients on chronic hemodialysis. Additionally, we also determined various clinical and biochemical data to assess their relationship to BMD at the different measurement sites. A total of 75% of our patients was found to have reduced BMD, and 25% had an average z-score below -2. Z-scores obtained by the different methods and at the different measurement sites within an individual patient varied considerably from completely normal to severely reduced values. Multivariate analyses using clinical and biochemical parameters showed lower values of BMD at all measurement sites after transplantation and marginally higher values after parathyroidectomy, which was seen only in DXA measurement at the femoral neck. We conclude from our study that determination of BMD in chronic hemodialysis patients yields highly variable results, depending on the technique used. As long as the exact clinical relevance of these results has not been determined, regular routine measurement of isolated sites of BMD cannot be advocated in this patient population.