Differences in prevalence of reduced and low bone mineral density between lumbar spine and femoral neck in peritoneal dialysis patients using dual-energy X-ray absorptiometry (DXA)

The pattern of chronic kidney disease–mineral bone disease has changed following the increase in elderly patients receiving dialysis, with escalating likelihood of osteoporosis, with associated increased fracture risk and mortality. Thus, we wished to determine the prevalence of osteoporosis in our peritoneal dialysis (PD) cohort. Lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA), and low BMD (osteoporosis) and reduced BMD (osteopenia) defined according to the World Health Organisation T scores. DXA scans from 734 patients, 57.2% male, mean age 61.0 ±16.0 years, 34.6% diabetic, with a median 8.0 (2–24) months of treatment with PD were reviewed. Fewer patients had normal BMD at the FN vs. LS (24.1 vs. 55%), and more classified as reduced (FN 55.9 vs. 34% LS) and low BMD (FN 17 vs. 11% LS), χ 2 112.2, p < 0.001. Agreement between FN and LS T scores was r = 0.36 with Spearman rank correlation, and 0.34 by Kendall’s tau b , Cohen’s kappa score 0.17, and Bland–Altman bias −0.37 (95% limits of agreement −1.8 to 1.08). The prevalence of reduced and low BMD was much greater when using FN T scores compared to LS, with LS T scores a mean of 0.34 higher than FN. DXA scanning at the LS can be affected by overlying vascular calcification and electron densities in the bowel, and as such we suggest that FN T scores are used to report BMD in PD patients.