Bone mineral density and biochemical markers of bone metabolism in predialysis patients with chronic kidney disease

Abstract

The aim of the study was to evaluate the usefulness of serum bone turnover markers (BTM) and bone mineral density (BMD) determined by dual-energy X-ray absorptiometry (DEXA) in predialysis patients with chronic kidney disease (CKD). We enrolled 83 patients with CKD, 41 (49.4%) males, 42 (50.6%) females, with mean estimated glomerular filtration rate (eGFR) 23.90±12 (range=6.0–56.0). BMD of the lumbar spine (LS) (anteroposterior, L2 through L4), femoral neck (FN) and femoral trochanter (FT) were measured by DEXA. Biochemical BTM, including calcium (Ca), phosphorus (P), intact parathyroid hormone (PTH), serum specific alkaline phosphatase (serum AP), bone-specific AP (BSAP), plasma bicarbonate and 25-hydroxy-vitamin D (25hD) were used for the prediction of BMD loss. T score results of LS and FN were worse than FT. BMD levels were lower in females than in males (all p<0.05). According to different BMD T score levels, patients with age ≥65 years and patients in menopause were significantly more osteopenic (p=0.026) and there was no relation between different BMD T scores and presence of diabetes (p=0.654). A positive correlation was identified between the BMD of FN T-Z scores (r=0.270, p=0.029, r=0.306, p=0.012), FT T-Z scores (r=0.220, p=0.076, r:0.250, p=0.043) and serum HCO3, while the correlation with serum alkaline phosphatase (AP) and BSAP was considered to be negative. No statistically significant association was found between BMD of all the measured skeletal sites and eGFR. Loss of BMD was identified mostly in females over ≥65 years of age and after menopause. Higher serum levels of BSAP and AP can be determined in the advanced stages of renal failure and they reflect fracture risk of the femur, but not spine. Measurements of BMD by DEXA are useful to demonstrate bone loss, but not technical enough to distinguish the quantity of bone loss between different stages of CKD.