Changes in bone mineral density at various sites in patients on hemodialysis due to chronic glomerulonephritis

Association of reduction in bone mineral density with mortality in male hemodialysis patients

In the present study we examined the relationship of bone mineral density (BMD) reduction with increased mortality in hemodialysis patients. A single-center prospective observational study was conducted on 269 male hemodialysis patients. The BMD in the distal third of the radius (DR1/3) and in the ultradistal radius (UR), which are enriched with cortical and cancellous bone, respectively, was measured twice using dual-energy X-ray absorptiometry (DXA) with a 1-year interval. Subjects were divided into two groups based on the presence or absence of BMD reduction. Survival was followed for 61.0 months, after which time 104 patients (39%) had died. A significant BMD reduction at the UR and DR1/3 occurred in 182 (68%) and 195 (72%) patients, respectively. Patients with BMD reduction in the UR, in contrast to the DR1/3, had a significantly lower survival rate than those without BMD reduction (P = 0.01). In Cox regression analysis, the rate of BMD change at the UR, in addition to patient age, diabetes mellitus, and serum albumin, emerged as an independent predictor for increased mortality (HR = 0.970, 95% CI 0.945-0.996). Our results suggest that BMD reduction at the UR might be a clinically relevant marker that predicts an increased risk of mortality in male hemodialysis patients.

Serum levels of TRAP5b, a new bone resorption marker unaffected by renal dysfunction, as a useful marker of cortical bone loss in hemodialysis patients

Tartrate-resistant acid phosphatase (TRAP) 5b is a new marker of bone resorption that is unaffected by renal dysfunction. The significance of TRAP5b was assessed in hemodialysis (HD) patients. Serum concentrations of TRAP5b and cross-linked N-telopeptide of type I collagen (NTX) were determined as bone resorption markers, and those of bone alkaline phosphatase (BAP) and intact osteocalcin (OC) were measured as bone formation markers in 58 HD patients. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry twice in the distal third of the radius, with a 2-year interval between measurements. Serum TRAP5b correlated significantly with BAP, intact OC, intact parathyroid hormone (PTH), and especially serum NTX. TRAP5b, NTX, BAP, and intact OC all correlated significantly with BMD at the time of the second measurement; and TRAP5b, NTX, and intact OC, but not BAP and intact PTH, correlated significantly with the annual change in BMD during the 2-year period. Among the bone markers, patients in the highest tertile for serum TRAP5b and intact OC showed the fastest rate of cortical bone loss. The sensitivity and specificity for detection of rapid bone loss were 57.9% and 76.9%, respectively, for serum TRAP5b. Measurement of serum TRAP5b, as well as intact OC, may be a clinically relevant assay for estimation of bone metabolic status in HD patients, although serum intact OC accumulates in uremic serum.

Serum concentrations of cross-linked N-telopeptides of type I collagen: new marker for bone resorption in hemodialysis patients

BACKGROUND

Urinary cross-linked N-telopeptide of type I collagen (NTX) is a reliable bone resorption marker in patients with metabolic bone disease. We assessed a clinically available serum NTX assay suitable for anuric patients on hemodialysis (HD).

METHODS

Serum concentrations of NTX, C-terminal telopeptide of type I collagen (beta-CTX), pyridinoline (PYD), and deoxypyridinoline (DPD) were determined as bone resorption markers, and those of bone alkaline phosphatase (BAP) and intact osteocalcin (OC) as bone formation markers, in 113 male HD patients (mean age, 59.3 years; mean HD duration, 67.7 months). Each patient's bone mineral density (BMD) in the distal third of the radius was measured twice, with a 2-year interval between measurements, by dual-energy x-ray absorptiometry.

RESULTS

Serum NTX correlated significantly with beta-CTX, PYD, DPD, BAP, and intact OC. NTX, as well as beta-CTX, PYD, DPD, BAP, and intact OC, correlated significantly with BMD at the time of measurement. NTX, beta-CTX, and DPD correlated significantly with the annual change in BMD during the 2-year period thereafter, in contrast to PYD, BAP, and intact OC. Patients in the highest quartile of serum NTX concentrations showed the fastest rate of bone loss. The sensitivity and specificity for detecting rapid bone loss were 48% and 83%, respectively, for serum NTX.

CONCLUSION

Serum NTX may provide a clinically relevant serum assay to estimate bone turnover in HD patients.

Serum levels of C-terminal telopeptide of type I collagen: a useful new marker of cortical bone loss in hemodialysis patients

Renal osteodystrophy is a major complication in hemodialysis patients. Measurement of serum peptide derived from the degradation of bone collagen could potentially provide an indirect estimate of bone resorption. The present study estimated the significance of the C-terminal telopeptide of type I collagen (beta-CTx) as a serum bone resorption marker in male hemodialysis patients. The mean age and hemodialysis duration of the 160 patients were 59.7 years (26-86 years) and 67.2 months (17-142 months), respectively. Bone mineral density (BMD) in the distal third of the radius was measured using dual-energy X-ray absorptiometry twice with a 2-year interval. A blood sample was collected immediately before the hemodialysis session at the time of the second BMD measurement. Other serum bone markers determined were bone-specific alkaline phosphatase (BAP) and intact and N-terminal midfragment (N-Mid) osteocalcin (OC) as bone-formation markers and serum pyridinoline (PYD) and deoxypyridinoline (DPD) as bone resorption markers. Serum beta-CTx correlated significantly in a positive manner with serum PYD, DPD, BAP, intact OC, and N-Mid OC. Serum beta-CTx, as well as PYD, DPD, BAP, intact OC, and N-Mid OC, correlated significantly with BMD in the distal third of the radius at the second measurement and with the rate of BMD reduction during the preceding 2 years. The highest quartile of serum beta-CTx was positively associated with rapid bone loss, defined as a change in the value for BMD in the distal third of the radius falling within the upper tertile of patients, in 55% of cases, and each quartile progress in serum beta-CTx increased the odds ratio of rapid bone loss by a factor of 1.73. Since the Youden index was twice as accurate for beta-CTx, BAP and N-Mid OC as for intact PTH, these bone-remodeling markers may be better risk markers of cortical bone loss than intact PTH. Inclusion in the highest quartile of PTH (above 288 pg/ml) predicted rapid bone loss with a sensitivity of only 26%. This means that the upper limit for serum PTH level recommended by K/DOQI may be too high, since 74% of cases with rapid bone loss showed serum PTH levels of below 288 pg/ml. In conclusion, serum measurement of beta-CTx may provide a new commercially viable and relevant serum assay to reflect cortical bone resorption in hemodialysis patients.

Diagnosis and monitoring of renal osteodystrophy

A variety of biochemical investigations and radiological techniques are available to assist in the diagnosis and monitoring of renal osteodystrophy. Measurement of serum parathyroid hormone remains the single most useful biochemical test in predicting bone histology in an individual patient. Newer biochemical markers of bone turnover are unlikely to supplant this in everyday practice, but may provide useful supplementary information in the future. The present review discusses the role of radiological investigation, including bone densitometry and quantitative ultrasound. Bone biopsy remains the 'gold standard' investigation. Its invasive nature and the need for specialized processing and interpretation limits its use in clinical practice, although it still has a role particularly in the investigation of low turnover states. Also, as molecular biological techniques are increasingly being used, the evaluation of biopsy specimens will in the future provide new insights into the disordered bone cell function that occurs in renal osteodystrophy.