Review article: Chronic kidney disease-mineral bone disorder: Have we got the assays right?

Prospective cohort study: Cinacalcet-mediated lowering of PTH level and cardiovascular disease mortality in younger Korean patients with stage 5 CKD at a Korean secondary hospital

WHAT IS KNOWN AND OBJECTIVES

Cinacalcet may reduce cardiovascular disease (CVD) mortality in elderly patients with chronic kidney disease (CKD). However, previous studies of the clinical responses to cinacalcet have exhibited discrepancies due to highly variable baseline levels of parathyroid hormone (PTH), kidney function and age. Little is known about the true effect of cinacalcet on stage 5 CKD. The objective of the current observational study was to evaluate whether cinacalcet-mediated lowering of PTH levels improves all-cause mortality and cardiovascular disease mortality in younger stage 5 CKD patients (mean age <55 years).

METHODS

This prospective, cohort study reviewed the electronic medical records (EMRs) of CKD patients (n=540) with secondary hyperparathyroidism (SHPT) for a period of 36 months. Of 540 patients, 104 subjects met the inclusion criteria and were included in the final evaluation (mean serum iPTH 688.7 pg/mL). Patients were divided into a cinacalcet group (n=43) and a non-cinacalcet group (n=61).

RESULTS AND DISCUSSION

Comparing the cinacalcet group to the non-cinacalcet group, Cox proportional hazard modelling found that all-cause mortality was five (31.3%) in the cinacalcet group and three (15.8%) in the non-cinacalcet group for patients with serum levels of PTH>600 pg/mL [P=.277, hazard ratio 2.213, 95% confidence interval (CI): 0.529-9.262]. Cardiovascular disease mortality (CVD: heart disease) occurred in two (5.3%) in the cinacalcet group and one (2.1%) in the non-cinacalcet group [P=.425, HR 2.611, 95% CI: 0.228-9.939]. Overall, there were no significant differences in CVD mortality between the two groups.

WHAT IS NEW AND CONCLUSION

Cinacalcet was not associated with decreases in all-cause mortality or CVD mortality in younger stage 5 CKD patients with high PTH levels (>600 pg/mL). This could be explained by the diversity of the population in terms of the patient's age, health insurance policies, target serum level of biochemical and PTH, and glomerular filtration rate (GFR) at admission. These data, although based on an observational study, indicate that adding cinacalcet to the current standard care for younger stage 5 CKD patients should be re-evaluated.

Assessment of bone turnover markers to predict mineral and bone disorder in men with pre-dialysis non-diabetic chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is commonly associated with disturbances in mineral metabolism and bone disease. Bone biopsy is the gold standard in diagnosing mineral bone disorder. Hence the search for non-invasive assessment of bone health gains importance. We undertook to assess the bone health in men with stage 4 and 5 chronic kidney Disease.

METHODS

We recruited 32 male subjects with Stage 4 and 5 chronic kidney disease and 32 age-matched healthy male controls. 25-hydroxyvitamin D, intact parathyroid hormone, and bone-specific alkaline phosphatase were assayed. Bone mineral density (BMD) was estimated using dual-energy X-ray absorptiometry.

RESULTS

CKD is associated with significantly higher levels of bone-specific alkaline phosphatase and intact parathyroid hormone and lower levels of 25-hydroxyvitamin D and bone mineral density, when compared to controls. In the multivariate linear regression model, bone-specific alkaline phosphatase emerged as an independent predictor of reduced BMD. Receiver Operator Characteristic analysis for prediction of reduced BMD in CKD showed both intact parathyroid hormone and bone-specific alkaline phosphatase have significant predicting power.

CONCLUSION

The combination of bone-specific alkaline phosphatase and intact parathyroid hormone has more significant predicting power and is a more reliable index for non-invasive assessment of bone health in men with chronic kidney disease, than either marker when used alone.

Recent advances in the noninvasive diagnosis of renal osteodystrophy

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is the term used to describe a constellation of biochemical abnormalities, bone disturbances that may lead to fractures, and extraskeletal calcification in soft tissues and arteries seen in CKD. This review focuses on the noninvasive diagnosis of renal osteodystrophy, the term used exclusively to define the bone pathology associated with CKD. Transiliac bone biopsy and histomorphometry with double-labeled tetracycline or its derivatives remains the gold standard for diagnosis of renal osteodystrophy. However, histomorphometry provides a 'window' into bone only at a single point in time, and is not clinically practical for studying continuous changes in bone morphology. Furthermore, the etiology of fractures in CKD is multifactorial and not fully explained by histomorphometry findings alone. The propensity of a bone to fracture is determined by bone strength, which is affected by bone mass and bone quality; the latter is a term used to describe the structure and composition of bone. Bone quantity is traditionally assessed by dual X-ray absorptiometry (DXA) and CT-based methods. Bone quality is more difficult to assess noninvasively, but newer techniques are emerging and are described in this review. Ultimately, the optimal diagnostic strategy for renal osteodystrophy may be a combination of multiple imaging techniques and biomarkers that are specific to each gender and race in CKD, with a goal of predicting fracture risk and optimizing therapy.

PTH--a particularly tricky hormone: why measure it at all in kidney patients?

Plasma parathyroid hormone (PTH) concentrations are commonly measured in the context of CKD, as PTH concentration elevation is typical in this clinical context. Much has been inferred from this raised PTH concentration tendency, both about the state of skeletal integrity and health and also about the potential clinical outcomes for patients. However, we feel that reliance on PTH concentrations alone is a dangerous substitute for the search for, and use of, more precise and reliable biomarkers. In this article, we rehearse these arguments, bringing together patient-level and analytical considerations for the first time.

KDOQI US commentary on the 2009 KDIGO Clinical Practice Guideline for the Diagnosis, Evaluation, and Treatment of CKD-Mineral and Bone Disorder (CKD-MBD)

This commentary provides a US perspective on the 2009 KDIGO (Kidney Disease: Improving Global Outcomes) Clinical Practice Guideline for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). KDIGO is an independent international organization with the primary mission of the promotion, coordination, collaboration, and integration of initiatives to develop and implement clinical practice guidelines for the care of patients with kidney disease. The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI), recognizing that international guidelines need to be adapted for each country, convened a group of experts to comment on the application and implementation of the KDIGO guideline for patients with CKD in the United States. This commentary puts the KDIGO guideline into the context of the supporting evidence and the setting of care delivered in the United States and summarizes important differences between prior KDOQI guidelines and the newer KDIGO guideline. It also considers the potential impact of a new bundled payment system for dialysis clinics. The KDIGO guideline addresses the evaluation and treatment of abnormalities of CKD-MBD in adults and children with CKD stages 3-5 on long-term dialysis therapy or with a kidney transplant. Tests considered are those that relate to laboratory, bone, and cardiovascular abnormality detection and monitoring. Treatments considered are interventions to treat hyperphosphatemia, hyperparathyroidism, and bone disease in patients with CKD stages 3-5D and 1-5T. Limitations of the evidence are discussed. The lack of definitive clinical outcome trials explains why most recommendations are not of level 1 but of level 2 strength, which means weak or discretionary recommendations. Suggestions for future research highlight priority areas.