The clinical utility of FRAX to discriminate fracture status in men and women with chronic kidney disease

Vertebral fractures in patients with CKD and the general population: a call for diagnosis and action

Vertebral fractures (VFs) are the most common osteoporotic fractures in the general population, and they have been associated with high mortality, decreased quality of life, and high risk of subsequent fractures, especially when recent, multiple, or severe. Currently, VF diagnosis and classification determine fracture risk and the most appropriate anti-osteoporotic treatment. However, VFs are clearly underdiagnosed, especially in patients with chronic kidney disease (CKD), and CKD-associated osteoporosis has been disregarded until recently. VFs are associated with higher morbidity and mortality, and their prevalence and incidence differ depending on the grade of renal dysfunction (CKD G1-G5) and/or the type of renal replacement therapy (dialysis or transplantation). In addition to classical risk factors [such as higher age, female sex, reduced bone mineral density, diabetes and steroid use], various other factors have been associated with an increased risk of VFs in CKD, including CKD grade, haemodialysis vintage, time since renal transplantation, low or high intact parathyroid hormone and phosphate levels, and/or vitamin D and K1 deficiencies. Importantly, several clinical societies have recently modified their algorithms according to the fracture risk classification (including the presence of VFs) and determined the most appropriate anti-osteoporotic treatment for the general population. However, there are no specific guidelines addressing this topic in patients with CKD despite an important paradigm shift regarding the prognostic value of bone mineral density in 2017 after the publication of the CKD-Mineral and Bone Disorder Kidney Disease: Improving Global Outcomes guidelines. A proactive attitude towards diagnosis, treatment, and research is proposed to avoid therapeutic nihilism.

Chronic Kidney Disease in Patients with Hip Fracture: Prevalence and Outcomes

Objective. Although the association between chronic kidney disease (CKD) and osteoporotic fractures is well established, data on CKD combined with hip fracture (HF) are scarce and controversial. We aimed to assess in patients with HF the prevalence of CKD, its impact on hospital mortality and length of stay (LOS) and to determine the prognostic value of CKD to predict hospital outcomes. Methods. Prospectively collected clinical data were analysed in 3623 consecutive HF patients aged ≥65 years (mean age 83.4 ± 7.50 [standard deviation] years; 74.4% females). Results. CKD among older patients with HF is highly prevalent (39.9%), has different clinical characteristics, a 2.5-fold higher mortality rate, and 40% greater risk of prolonged LOS. The strongest risk for a poor outcome was advanced age (>80 years). The risk of death substantially increases in combination with chronic disorders, especially coronary artery disease, anaemia, hyperparathyroidism, and atrial fibrillation; models based only on three variables—CKD stage, age >80, and presence of a specific chronic condition—predicted in-hospital death with good discrimination capability (AUC ≥ 0.700) and reasonable accuracy, the number needed to predict ranged between 5.7 and 14.5. Only 12% of HF patients received osteoporotic drugs prefracture. Conclusion. In HF patients with CKD, the risk of adverse outcomes largely increases in parallel with worsening kidney function and, especially, in combination with comorbidities; models based on three admission variables predict a fatal outcome. Assessment of renal function is essential to preventing osteoporotic fractures.

Post-Transplant Bone Disease in Kidney Transplant Recipients: Diagnosis and Management

Kidney transplantation is the preferred gold standard modality of treatment for kidney failure. Bone disease after kidney transplantation is highly prevalent in patients living with a kidney transplant and is associated with high rates of hip fractures. Fractures are associated with increased healthcare costs, morbidity and mortality. Post-transplant bone disease (PTBD) includes renal osteodystrophy, osteoporosis, osteonecrosis and bone fractures. PTBD is complex as it encompasses pre-existing chronic kidney disease-mineral bone disease and compounding factors after transplantation, including the use of immunosuppression and the development of de novo bone disease. After transplantation, the persistence of secondary and tertiary hyperparathyroidism, renal osteodystrophy, relative vitamin D deficiency and high levels of fibroblast growth factor-23 contribute to post-transplant bone disease. Risk assessment includes identifying both general risk factors and kidney-specific risk factors. Diagnosis is complex as the gold standard bone biopsy with double-tetracycline labelling to diagnose the PTBD subtype is not always readily available. Therefore, alternative diagnostic tools may be used to aid its diagnosis. Both non-pharmacological and pharmacological therapy can be employed to treat PTBD. In this review, we will discuss pathophysiology, risk assessment, diagnosis and management strategies to manage PTBD after kidney transplantation.

Fibroblast growth factor 23 and its role in bone diseases

Fibroblast growth factor 23 (FGF23) has been casually linked to numerous hypophosphatemic bone diseases, however connection with bone loss or fragility fractures is still a matter of debate. The purpose of this review is to explore and summarise the known actions of FGF23 in various pathological bone conditions. Besides implication in bone mineralisation, elevated FGF23 showed a pathological effecton bone remodelling, primarily by inhibiting osteoblast function. Unlike the weak association with bone mineral density, high values of FGF23 have been connected with fragility fracture prevalence. This review shows that its effects on bone are concomitantly present on multiple levels, affecting both qualitative and quantitative part of bone strength, eventually leading to impaired bone strength and increased tendency of fractures. Recognising FGF23 as a risk factor for the development of bone diseases and correcting its levels could lead to the reduction of morbidity and mortality in specific groups of patients.

[Diagnosis and treatment of osteoporosis in patients with chronic kidney disease : Joint guidelines of the Austrian Society for Bone and Mineral Research (ÖGKM), the Austrian Society of Physical and Rehabilitation Medicine (ÖGPMR) and the Austrian Society of Nephrology (ÖGN)]

DEFINITION AND EPIDEMIOLOGY

Chronic kidney disease (CKD): abnormalities of kidney structure or function, present for over 3 months. Staging of CKD is based on GFR and albuminuria (not graded). Osteoporosis: compromised bone strength (low bone mass, disturbance of microarchitecture) predisposing to fracture. By definition, osteoporosis is diagnosed if the bone mineral density T‑score is ≤ -2.5. Furthermore, osteoporosis is diagnosed if a low-trauma (inadequate trauma) fracture occurs, irrespective of the measured T‑score (not graded). The prevalence of osteoporosis, osteoporotic fractures and CKD is increasing worldwide (not graded). PATHOPHYSIOLOGY, DIAGNOSIS AND TREATMENT OF CHRONIC KIDNEY DISEASE-MINERAL AND BONE DISORDER (CKD-MBD): Definition of CKD-MBD: a systemic disorder of mineral and bone metabolism due to CKD manifested by either one or a combination of the following: abnormalities of calcium, phosphorus, PTH, or vitamin D metabolism; renal osteodystrophy; vascular calcification (not graded). Increased, normal or decreased bone turnover can be found in renal osteodystrophy (not graded). Depending on CKD stage, routine monitoring of calcium, phosphorus, alkaline phosphatase, PTH and 25-OH-vitamin D is recommended (2C). Recommendations for treatment of CKD-MBD: Avoid hypercalcemia (1C). In cases of hyperphosphatemia, lower phosphorus towards normal range (2C). Keep PTH within or slightly above normal range (2D). Vitamin D deficiency should be avoided and treated when diagnosed (1C).

DIAGNOSIS AND RISK STRATIFICATION OF OSTEOPOROSIS IN CKD

Densitometry (using dual X‑ray absorptiometry, DXA): low T‑score correlates with increased fracture risk across all stages of CKD (not graded). A decrease of the T‑score by 1 unit approximately doubles the risk for osteoporotic fracture (not graded). A T-score ≥ -2.5 does not exclude osteoporosis (not graded). Bone mineral density of the lumbar spine measured by DXA can be increased and therefore should not be used for the diagnosis or monitoring of osteoporosis in the presence of aortic calcification, osteophytes or vertebral fracture (not graded). FRAX can be used to aid fracture risk estimation in all stages of CKD (1C). Bone turnover markers can be measured in individual cases to monitor treatment (2D). Bone biopsy may be considered in individual cases, especially in patients with CKD G5 (eGFR < 15 ml/min/1.73 m2) or CKD 5D (dialysis).

SPECIFIC TREATMENT OF OSTEOPOROSIS IN PATIENTS WITH CKD

Hypocalcemia should be treated and serum calcium normalized before initiating osteoporosis therapy (1C). CKD G1-G2 (eGFR ≥ 60 ml/min/1.73 m2): treat osteoporosis as recommended for the general population (1A). CKD G3-G5D (eGFR < 60 ml/min/1.73 m2 to dialysis): treat CKD-MBD first before initiating osteoporosis treatment (2C). CKD G3 (eGFR 30-59 ml/min/1.73 m2) with PTH within normal limits and osteoporotic fracture and/or high fracture risk according to FRAX: treat osteoporosis as recommended for the general population (2B). CKD G4-5 (eGFR < 30 ml/min/1.73 m2) with osteoporotic fracture (secondary prevention): Individualized treatment of osteoporosis is recommended (2C). CKD G4-5 (eGFR < 30 ml/min/1.73 m2) and high fracture risk (e.g. FRAX score > 20% for a major osteoporotic fracture or > 5% for hip fracture) but without prevalent osteoporotic fracture (primary prevention): treatment of osteoporosis may be considered and initiated individually (2D). CKD G4-5D (eGFR < 30 ml/min/1.73 m2 to dialysis): Calcium should be measured 1-2 weeks after initiation of antiresorptive therapy (1C).

PHYSICAL MEDICINE AND REHABILITATION

Resistance training prioritizing major muscle groups thrice weekly (1B). Aerobic exercise training for 40 min four times per week (1B). Coordination and balance exercises thrice weekly (1B). Flexibility exercise 3-7 times per week (1B).

Recommendations of the Spanish Society of Nephrology for the management of mineral and bone metabolism disorders in patients with chronic kidney disease: 2021 (SEN-MM)

As in 2011, when the Spanish Society of Nephrology (SEN) published the Spanish adaptation to the Kidney Disease: Improving Global Outcomes (KDIGO) universal Guideline on Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD), this document contains an update and an adaptation of the 2017 KDIGO guidelines to our setting. In this field, as in many other areas of nephrology, it has been impossible to irrefutably answer many questions, which remain pending. However, there is no doubt that the close relationship between the CKD-MBD/cardiovascular disease/morbidity and mortality complex and new randomised clinical trials in some areas and the development of new drugs have yielded significant advances in this field and created the need for this update. We would therefore highlight the slight divergences that we propose in the ideal objectives for biochemical abnormalities in the CKD-MBD complex compared to the KDIGO suggestions (for example, in relation to parathyroid hormone or phosphate), the role of native vitamin D and analogues in the control of secondary hyperparathyroidism and the contribution of new phosphate binders and calcimimetics. Attention should also be drawn to the adoption of important new developments in the diagnosis of bone abnormalities in patients with kidney disease and to the need to be more proactive in treating them. In any event, the current speed at which innovations are taking place, while perhaps slower than we might like, globally drives the need for more frequent updates (for example, through Nefrología al día).

Management of osteoporosis in patients with chronic kidney disease

Patients with CKD have a 4-fivefold higher rate of fractures. The incidence of fractures increases with deterioration of kidney function. The process of skeletal changes in CKD patients is characterized by compromised bone strength because of deterioration of bone quantity and/or quality. The fractures lead to a deleterious effect on the quality of life and higher mortality in patients with CKD. The pathogenesis of bone loss and fracture is complex and multi-factorial. Renal osteodystrophy, uremic milieu, drugs, and systemic diseases that lead to renal failure all contribute to bone damage in CKD patients. There is no consensus on the optimal diagnostic method of compromised bone assessment in patients with CKD. Bone quantity and mass can be assessed by dual-energy x-ray absorptiometry (DXA) or quantitative computed tomography (QCT). Bone quality on the other side can be assessed by non-invasive methods such as trabecular bone score (TBS), high-resolution bone imaging methods, and invasive bone biopsy. Bone turnover markers can reflect bone remodeling, but some of them are retained by kidneys. Understanding the mechanism of bone loss is pivotal in preventing fracture in patients with CKD. Several non-pharmacological and therapeutic interventions have been reported to improve bone health. Controlling laboratory abnormalities of CKD-MBD is crucial. Anti-resorptive therapies are effective in improving BMD and reducing fracture risk, but there are uncertainties about safety and efficacy especially in advanced CKD patients. Accepting the prevalent of low bone turnover in patients with advanced CKD, the osteo-anabolics are possibly promising. Parathyroidectomy should be considered a last resort for intractable cases of renal hyperparathyroidism. There is a wide unacceptable gap in osteoporosis management in patients with CKD. This article is focusing on the updated management of CKD-MBD and osteoporosis in CKD patients. Chronic kidney disease deteriorates bone quality and quantity. The mechanism of bone loss mainly determines pharmacological treatment. DXA and QCT provide information about bone quantity, but assessing bone quality, by TBS, high-resolution bone imaging, invasive bone biopsy, and bone turnover markers, can guide us about the mechanism of bone loss.

Trabecular bone score and phalangeal quantitative ultrasound are associated with muscle strength and fracture risk in hemodialysis patients

There is growing interest in the relationship between chronic kidney disease (CKD) and fragility fracture risk. Bone mineral density (BMD) is a major determinant of bone strength, although its role as a predictor of fracture in advanced CKD and hemodialysis is still under debate. We aimed to further investigate surrogates of bone quality and their associations with muscle strength and fracture risk in hemodialysis. Multiple clinical risk factors for fracture and an estimated 10-year probability of fracture, BMD at lumbar spine and femur, trabecular bone score (TBS), X-ray vertebral morphometry, phalangeal bone quantitative ultrasonography (QUS), tibial pulse-echo ultrasonography (PEUS), and handgrip strength were evaluated in a setting of hemodialysis patients in treatment with acetate-free biofiltration (AFB) or bicarbonate hemodialysis. The bone ultrasound measurements, both at phalangeal and tibial sites, were significantly associated with lumbar and femoral DXA values. Handgrip strength was significantly associated with the 10-year probability of fracture (r = -0.57, p < 0.001 for major fractures and r = -0.53, p < 0.001 for hip fracture, respectively), with femur neck, total femur, and L1-L4 BMD values (r = 0.47, p = 0.04; r = 0.48, p = 0.02; r = 0.58, p = 0.007, respectively), with TBS at the lumbar spine (r = 0.71, p < 0.001) and with the phalangeal QUS measure of AD-SoS (r = 0.369, p = 0.023). In the hemodialysis group, 10 participants (24.3%) reported at least one morphometric vertebral fracture (Vfx); conversely, only six participants (15%) showed Vfx in the control group. In the hemodialysis group, participants with Vfx compared with participants without Vfx reported significantly different TBS, bone transmission time (BTT), cortical thickness, and handgrip strength (p < 0.05). At multiple regression analysis, by identifying as dependent variable the 10-year fracture risk for major fracture, after correcting for age, BMI, time since dialysis, AD-SoS, cortical bone thickness, and handgrip strength, only BTT (β = -15.21, SE = 5.91, p = 0.02) and TBS (β = -54.69, SE = 21.88, p = 0.02) turned out as independently associated with fracture risk. In conclusion, hemodialysis patients showed a higher fracture risk and lower surrogate indices of bone strength as TBS and QUS parameters. In this cohort of patients, handgrip strength measurements appeared to be a useful instrument to identify high-fracture-risk subjects.

Role of Fracture Risk Assessment Tool and Bone Turnover Markers in Predicting All-Cause and Cardiovascular Mortality in Hemodialysis Patients

Background

Fracture Risk Assessment Tool (FRAX) and bone turnover markers (BTMs) predict fractures in the general population. However, the role of FRAX and BTMs in predicting mortality remains uncertain in hemodialysis (HD) patients.

Methods

One hundred and sixty-four HD patients stratified by low or high risk of 10-year fracture probability using FRAX. High risk of fracture was defined as 10-year probability of hip fracture ≥3% or major osteoporotic fracture ≥20%. The association of high risk of fracture and BTMs with all-cause mortality and cardiovascular (CV) mortality were evaluated using multivariate-adjusted Cox regression analysis.

Results

Eighty-five (51.8%) patients were classified as high risk of fracture based on FRAX among 164 HD patients. During a mean follow-up period of 3.5 ± 1.0 years, there were 39 all-cause deaths and 23 CV deaths. In multivariate-adjusted Cox regression, high risk of fracture based on FRAX was independently associated with all-cause mortality [hazard ratio (HR): 2.493, 95% confidence interval (CI): 1.026–6.056, p = 0.044) but not with CV mortality (HR: 2.129, 95% CI: 0.677–6.700, p = 0.196). There were no associations between BTMs and mortality risk. Furthermore, lower geriatric nutritional risk index (GNRI) was significantly associated with increased CV mortality (HR: 0.888, 95% CI: 0.802–0.983, p = 0.022) after adjusting by confounding variables.

Conclusion

High risk of fracture using FRAX was an independent predictor of all-cause mortality in patients undergoing HD. FRAX, rather than BTMs, has an important role of prognostic significance in HD patients.

Prevalence and predictors of asymptomatic vertebral fracture in patients with end-stage renal disease

Objective

This study aimed to investigate the prevalence and predictors of asymptomatic vertebral fracture in patients with end-stage renal disease undergoing hemodialysis.

Methods

This cross-sectional study included 80 patients with end-stage renal disease undergoing hemodialysis. Medical history, Fracture Risk Assessment Tool and anteroposterior and lateral radiographs of the thoracolumbar and lumbosacral spine were obtained. Vertebral fractures were identified using the Genant semiquantitative assessment.

Results

Radiography demonstrated asymptomatic vertebral fracture in 22 patients (27.5%). FRAX® results for major osteoporotic fracture (area under the curve, 0.64) and hip fracture (area under the curve, 0.62) were able to discriminate patients with prevalent asymptomatic vertebral fracture. A multivariate analysis demonstrated that a 1-year average corrected calcium (odds ratio, 0.38), steroid use (odds ratio, 8.99), and a serum albumin concentration <25 g/dL (odds ratio, 28.82) significantly predicted prevalent asymptomatic vertebral fracture (clinical model; area under the curve, 0.82). Combining the 1-year average corrected calcium and serum albumin concentration <25 g/dL with FRAX® results for major osteoporotic fracture (area under the curve, 0.78) and FRAX® results for hip (area under the curve, 0.75) produced a significantly greater area under the curve value to predict fracture when compared with FRAX® result for major osteoporotic fracture and FRAX® result for hip (P = 0.022).

Conclusion

Asymptomatic vertebral fracture is prevalent. FRAX® results for major osteoporotic fracture and hip provided lower ability in predicting asymptomatic vertebral facture when compared to the clinical model. Combining a 1-year average corrected calcium and serum albumin concentration <25 g/dL with FRAX® result for major osteoporotic fracture or hip improved the model's performance and provided comparable area under the curve to the clinical model.

Diagnosis and management of osteoporosis in chronic kidney disease stages 4 to 5D: a call for a shift from nihilism to pragmatism

The European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) CKD-MBD working group, in collaboration with the Committee of Scientific Advisors of the International Osteoporosis Foundation, published a position paper for the diagnosis and management of osteoporosis in patients with CKD stages 4-5D (eGFR < 30 ml/min 1.73 m²). The present article reports and summarizes the main recommendations included in this 2021 document. The following areas are reviewed: diagnosis of osteoporosis; risk factors for fragility fractures; fracture risk assessment; intervention thresholds for pharmacological intervention; general and pharmacological management of osteoporosis; monitoring of treatment, and systems of care, all in patients with CKD stages 4-5D. Guidance is provided for clinicians caring for CKD stages 4-5D patients with osteoporosis, allowing for a pragmatic individualized diagnostic and therapeutic approach as an alternative to current variations in care and treatment nihilism.

Lower Geriatric Nutritional Risk Index (GNRI) Is Associated with Higher Risk of Fractures in Patients Undergoing Hemodialysis

BACKGROUND

Although malnutrition and bone fracture are both major complications in patients undergoing hemodialysis, their association has not been clarified. The aim of our study was to clarify the association between the geriatric nutritional risk index (GNRI), an indicator of nutritional status, and the incidence of bone fractures in patients undergoing hemodialysis.

METHODS

We included 1342 registered patients undergoing hemodialysis and performed a post hoc analysis. We divided patients into the high GNRI group (≥92), considered to have a low risk of malnutrition, and the low GNRI group (<92), considered to have a high risk of malnutrition. Fracture-free survival in the low and high GNRI groups was evaluated by the Kaplan-Meier method. Cox proportional hazards models were used to identify the risk factors for fractures requiring hospitalization. All results were stratified by sex.

RESULTS

New bone fractures developed in 108 (8.0%) patients in 5 years of follow-up. Bone fractures occurred more frequently in the low GNRI group compared with the high GNRI group (HR: 3.51, 95% CI: 1.91-6.42, p < 0.01 in males; HR: 2.47, 95% CI: 1.52-4.03, p < 0.01 in females). A low GNRI was significantly associated with an increased incidence of bone fractures, even after adjustment for covariates. However, the serum levels of calcium, phosphate, parathyroid hormone, and alkaline phosphatase were not associated with the incidence of bone fractures.

CONCLUSIONS

A low GNRI is an independent risk factor for bone fractures in patients undergoing hemodialysis. Early intervention for the low GNRI group may be important in preventing the occurrence of fractures.

The renal patient seen by non-renal physicians: the kidney embedded in the 'milieu intérieur'

Chronic kidney disease is defined as a decrease in renal function or evidence of kidney injury for >3 months. This represents an oversimplification that may confuse physicians. Thus kidney function is equated to glomerular filtration rate, which represents one of multiple kidney functions. Some potentially more important renal functions are lost earlier, such as the production for the anti-ageing factor Klotho. Overall, these changes modify the emergent properties of the body, altering the relationships between different organs and systems, in a manner that is difficult to predict the response to interventions based on normal physiology concepts, as there is a novel steady state of interorgan relations. In this regard we now discuss the impact of CKD on heart failure; osteomuscular and joint pain and bone fragility and fractures; and osteosarcopaenia as seen by a cardiologist, a rheumatologist and a geriatrician.

Bone Fragility Fractures in CKD Patients

Chronic kidney diseases (CKD) are associated with mineral and bone diseases (MBD), including pain, bone loss, and fractures. Bone fragility related to CKD includes the risk factors observed in osteoporosis in addition to those related to CKD, resulting in a higher risk of mortality related to fractures. Unawareness of such complications led to a poor management of fractures and a lack of preventive approaches. The current guidelines of the Kidney Disease Improving Global Outcomes (KDIGO) recommend the assessment of bone mineral density if results will impact treatment decision. In addition to bone density, circulating biomarkers of mineral, serum bone turnover markers, and imaging techniques are currently available to evaluate the fracture risk. The purpose of this review is to provide an overview of the epidemiology and pathogenesis of CKD-associated bone loss. The contribution of the current tools and other techniques in development are discussed. We here propose a current view of how to better predict bone fragility and the therapeutic options in CKD.

European Consensus Statement on the diagnosis and management of osteoporosis in chronic kidney disease stages G4-G5D

Controlling the excessive fracture burden in patients with chronic kidney disease (CKD) Stages G4-G5D remains an impressive challenge. The reasons are 2-fold. First, the pathophysiology of bone fragility in patients with CKD G4-G5D is complex and multifaceted, comprising a mixture of age-related (primary male/postmenopausal), drug-induced and CKD-related bone abnormalities. Second, our current armamentarium of osteoporosis medications has not been developed for, or adequately studied in patients with CKD G4-G5D, partly related to difficulties in diagnosing osteoporosis in this specific setting and fear of complications. Doubts about the optimal diagnostic and therapeutic approach fuel inertia in daily clinical practice. The scope of the present consensus paper is to review and update the assessment and diagnosis of osteoporosis in patients with CKD G4-G5D and to discuss the therapeutic interventions available and the manner in which these can be used to develop management strategies for the prevention of fragility fracture. As such, it aims to stimulate a cohesive approach to the management of osteoporosis in patients with CKD G4-G5D to replace current variations in care and treatment nihilism.

Osteoporosis in Patients with Chronic Kidney Diseases: A Systemic Review

Chronic kidney disease (CKD) is associated with the development of mineral bone disorder (MBD), osteoporosis, and fragility fractures. Among CKD patients, adynamic bone disease or low bone turnover is the most common type of renal osteodystrophy. The consequences of CKD-MBD include increased fracture risk, greater morbidity, and mortality. Thus, the goal is to prevent the occurrences of fractures by means of alleviating CKD-induced MBD and treating subsequent osteoporosis. Changes in mineral and humoral metabolism as well as bone structure develop early in the course of CKD. CKD-MBD includes abnormalities of calcium, phosphorus, PTH, and/or vitamin D; abnormalities in bone turnover, mineralization, volume, linear growth, or strength; and/or vascular or other soft tissue calcification. In patients with CKD-MBD, using either DXA or FRAX to screen fracture risk should be considered. Biomarkers such as bALP and iPTH may assist to assess bone turnover. Before initiating an antiresorptive or anabolic agent to treat osteoporosis in CKD patients, lifestyle modifications, such as exercise, calcium, and vitamin D supplementation, smoking cessation, and avoidance of excessive alcohol intake are important. Managing hyperphosphatemia and SHPT are also crucial. Understanding the complex pathogenesis of CKD-MBD is crucial in improving one's short- and long-term outcomes. Treatment strategies for CKD-associated osteoporosis should be patient-centered to determine the type of renal osteodystrophy. This review focuses on the mechanism, evaluation and management of patients with CKD-MBD. However, further studies are needed to explore more details regarding the underlying pathophysiology and to assess the safety and efficacy of agents for treating CKD-MBD.

Bone fragility in patients with chronic kidney disease

Mineral and bone diseases (MBD) are predominant in patients with chronic kidney disease (CKD) and lead to several bone manifestations, from pain to skeletal fractures. Cumulative traditional clinical risk factors, such as age and gender, in addition to those related to CKD, enhance the risk of comorbidity and mortality related to fractures. Despite great advances in understanding MBD in CKD, clinical and biological targets are lacking, which leads to under-management of fractures. Optimal PTH control results in a net improvement in defining the levels of bone remodeling. In addition, circulating biomarkers such as bone-specific alkaline phosphatase and cross-linked collagen type I peptide will also provide additional information about remodeling rate, bone mineralization and the evaluation of fracture risk. Imaging techniques identify patients at risk by measurement of bone mineral density by DEXA or by high peripheral QCT, which allow the discrimination of trabecular and cortical bone. Here, we have reviewed the literature related to epidemiology and the pathophysiological role of mineral and biochemical factors involved in CKD-MBD with a special focus on fracture risk. We also provide an algorithm that could be used for the management of bone diseases and to guide treatment decisions. Finally, the combined expertise of clinicians from various disciplines is crucial for the best prevention of fractures.

FRAX prognostic and intervention thresholds in the management of major bone fractures in hemodialysis patients: A two-year prospective multicenter cohort study

PURPOSE

The usefulness of FRAX in predicting major bone fractures in patients with end-stage kidney disease on maintenance hemodialysis treatment has been confirmed in previous studies. For meaningful clinical use, the prognostic and intervention FRAX thresholds need to be established.

METHODS

The primary aim of our study was to calculate the optimal cut-off point of FRAX for the best prediction of an increased bone fracture risk in dialysis patients and additionally, to propose its intervention threshold, indicating the need for antifracture pharmacological treatment. The study included 718 hemodialysis patients, who were followed up for two years. Thirty low-energy major bone fractures were diagnosed during the study period. We used the Polish version of FRAX (without the DXA examination) and some particular variables of the FRAX calculator. The optimal cut-off point for prediction of an increased major bone fracture risk was based on the analysis of the sensitivity and specificity curves of FRAX.

RESULTS

The analysis revealed FRAX >5% (sensitivity of 70.0%, specificity of 69.8%) as the prognostic threshold for major bone fractures. Its sensitivity for bone fracture prediction was significantly higher, but specificity lower than those of FRAX ≥10%, used in general Polish population. The reason for this can be an underestimation of bone fracture risk with FRAX in dialysis patients.

CONCLUSIONS

We conclude that the FRAX prognostic threshold for identification of an increased risk of major bone fractures in hemodialysis patients is >5%. We propose to use this specific value of FRAX as an intervention threshold for pharmacological antifracture treatment in hemodialysis patients.

Prediction of Low and Very Low Bone Mineral Density Among Adult Survivors of Childhood Cancer

PURPOSE

To develop and validate prediction models for low and very low bone mineral density (BMD) on the basis of clinical and treatment characteristics that identify adult survivors of childhood cancer who require screening by dual-energy x-ray absorptiometry.

PATIENTS AND METHODS

White survivors of childhood cancer (n = 2,032; median attained age, 29.3 years [range, 18.1 to 40.9 years]) enrolled in the St Jude Lifetime Cohort (SJLIFE; development) and survivors treated at the Erasmus Medical Center (validation) in the Netherlands (n = 403; median age, 24.2 years [range, 18.0 to 40.9 years]) were evaluated with dual-energy x-ray absorptiometry to determine lumbar spine BMD and total-body BMD. Low and very low BMD were defined as lumbar spine BMD and/or total-body BMD z scores of -1 or lower or -2 or lower, respectively. Multivariable logistic regression was used to build prediction models; performance was assessed using receiver operating characteristic curves. Diagnostic values were calculated at different probabilities.

RESULTS

Low BMD was present in 51% and 45% of SJLIFE and Dutch participants, respectively, and very low BMD was present in 20% and 10%, respectively. The model for low BMD included male sex (odds ratio [OR], 3.07), height (OR, 0.95), weight (OR, 0.98), attained age (OR, 0.97), current smoking status (OR, 1.48), and cranial irradiation (OR, 2.11). Areas under the curve were 0.72 (95% CI, 0.70 to 0.75) in the SJLIFE cohort and 0.69 (95% CI, 0.64 to 0.75) in the Dutch cohort. The sum of the sensitivity (69.0%) and specificity (64.0%) was maximal at the predicted probability of 50%. The model for very low BMD included male sex (OR, 3.28), height (OR, 0.95), weight (OR, 0.97), attained age (OR, 0.98), cranial irradiation (OR, 2.07), and abdominal irradiation (OR, 1.61), yielding areas under the curve of 0.76 (95% CI, 0.73 to 0.78; SJLIFE cohort) and 0.75 (95% CI, 0.67 to 0.83; Dutch cohort).

CONCLUSION

Validated prediction models for low and very low BMD, using easily measured patient and treatment characteristics, correctly identified BMD status in most white adult survivors through age 40 years.

Association of Bone Mineral Density With Fractures Across the Spectrum of Chronic Kidney Disease: The Regina CKD-MBD Study

Background:

Recent studies have demonstrated that measurement of areal bone mineral density by dual-energy x-ray absorptiometry (DXA) predicts fractures in patients with chronic kidney disease (CKD). However, whether fracture risk prediction through bone mineral density (BMD) is enhanced due to the assessment of biochemical markers of chronic kidney disease and mineral and bone disease (CKD-MBD) or clinical risk factors is not clear. We hypothesized that in a select cohort of patients managed in a CKD clinic, that combining T-Scores with biochemical markers would optimize fracture discrimination than using DXA alone.

Objective:

To examine the relationships among BMD, biochemical markers of CKD-MBD, and fracture risk across Kidney Disease Improving Global Outcomes (KDIGO) glomerular filtration rate (GFR) categories G3a to G5.

Design:

Retrospective study.

Setting:

Patients were recruited from the multidisciplinary CKD clinic, Regina General Hospital, Canada.

Patients:

A total of 374 patients who received a DXA scan upon initial referral to Regina Multidisciplinary CKD Program from January 31, 2001 to January 31, 2010, were included in this study. The patients were followed for a total of 5 years.

Methods:

We conducted a retrospective review of 374 consecutive patients who underwent DXA imaging at the point of entry into our multidisciplinary CKD program. Areal BMD, T- and Z-Scores were obtained at the lumbar spine, total hip, mean of left and right femoral neck, and the one-third radius. We collected data on demographic, cross-sectional biochemical markers of mineral metabolism and fractures (identified through self-reported questionnaires, hospital electronic medical records, and physician billing records). We were able to gather data on 8/11 variables of Fracture Risk Assessment (FRAX) tool.

Results:

In our cohort, 14.3% of GFR categories G3a and G3b, 15.7% of GFR category G4, and 19.7% of GFR category G5 experienced a clinical fracture during the study period. On multivariate analysis, each decline of 1.0 SD in total hip BMD T-Score was associated with a significant increase in the risk of fracture (OR = 1.46, 95% confidence interval [CI], 1.12-1.89). Adding CKD-MBD markers and clinical risk factors did not further contribute to the model. Low BMD was the only independent risk factor for fracture in patients with CKD.

Limitations:

Self-reporting by patients and administrative records were used to identify fractures. We did not perform spine imaging to ascertain morphometric vertebral fractures. We were unable to gather all 11 variables of FRAX score and information on ethnicity. We were unable to capture site of fracture (hips, spine, etc) from billing records. Albumin excretion rates were not collected at baseline. Treatment of the underlying bone disease with pharmacotherapeutic agents may have attenuated patients’ fracture risk and thus underestimated the association between BMD and future fracture.

Conclusions:

Our findings confirm that BMD predicts fracture. The addition of cross-sectional CKD-MBD parameters and clinical risk factors to BMD did not add to fracture prediction. Prospective studies should investigate the utility of longitudinal biochemical markers on improving fracture risk assessment.

Fracture risk and treatment in chronic kidney disease

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is associated with the development of mineral bone disorder (MBD), osteoporosis, and fragility fractures. The purpose of this review is to provide an update on recent findings in the diagnosis and treatment of osteoporosis in patients with CKD.

RECENT FINDINGS

Multiple observational studies have shown that bone mineral density measurement using DEXA is equally predictive in CKD stages 1-3, as in the general population. Post hoc analyses from randomized trials of bisphosphonates, SERM, RANKL inhibitors and PTH agonists all suggest equal efficacy in mild-moderate CKD. A recent systematic review also found evidence for efficacy of bisphosphonates in patients with a kidney transplant.

SUMMARY

Bone mineral density measurement using DEXA is accurate in patients with CKD stages 1-3 and should be considered to guide treatment of osteoporosis. Current treatments are unaffected by mild-to-moderate decline in kidney function, and physicians should use bisphosphonates and other osteoporosis treatments in this population, whenever indicated. Studies evaluating the optimal diagnostic and management strategy in patients with CKD stages (G4-5D) are needed.

Rethinking Bone Disease in Kidney Disease

Renal osteodystrophy (ROD) is the bone component of chronic kidney disease mineral and bone disorder (CKD-MBD). ROD affects bone quality and strength through the numerous hormonal and metabolic disturbances that occur in patients with kidney disease. Collectively these disorders in bone quality increase fracture risk in CKD patients compared with the general population. Fractures are a serious complication of kidney disease and are associated with higher morbidity and mortality compared with the general population. Furthermore, at a population level, fractures are at historically high levels in patients with end-stage kidney disease (ESKD), whereas in contrast the general population has experienced a steady decline in fracture incidence rates. Based on these findings, it is clear that a paradigm shift is needed in our approach to diagnosing and managing ROD. In clinical practice, our ability to diagnose ROD and initiate antifracture treatments is impeded by the lack of accurate noninvasive methods that identify ROD type. The past decade has seen advances in the noninvasive measurement of bone quality and strength that have been studied in kidney disease patients. Below we review the current literature pertaining to the epidemiology, pathology, diagnosis, and management of ROD. We aim to highlight the pressing need for a greater awareness of this condition and the need for the implementation of strategies that prevent fractures in kidney disease patients. Research is needed for more accurate noninvasive assessment of ROD type, clinical studies of existing osteoporosis therapies in patients across the spectrum of kidney disease, and the development of CKD-specific treatments. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

A brief history of FRAX

This paper reviews the research programme that went into the development of FRAX® and its impact in the 10 years since its release in 2008.

INTRODUCTION

Osteoporosis is defined on the measurement of bone mineral density though the clinical consequence is fracture. The sensitivity of bone mineral density measurements for fracture prediction is low, leading to the development of FRAX to better calculate the likelihood of fracture and target anti-osteoporosis treatments.

METHODS

The method used in this paper is literature review.

RESULTS

FRAX, developed over an 8-year period, was launched in 2008. Since the launch of FRAX, models have been made available for 64 countries and in 31 languages covering more than 80% of the world population.

CONCLUSION

FRAX provides an advance in fracture risk assessment and a reference technology platform for future improvements in performance characteristics.

Predictors of bone fractures in a single-centre cohort of hemodialysis patients: a 2-year follow-up study

PURPOSE

Bone involvement represents one of the complications of end-stage chronic kidney disease, with fractures being its major risk. The aim of our study was to assess the frequency and predictors of low-trauma fractures in a cohort of maintenance hemodialysis patients followed-up on for 2 years.

METHODS

59 patients (67.6 ± 13.1 years, 43 males) treated with hemodiafiltration underwent initially laboratory (markers of calcium-phosphate metabolism and bone turnover markers) and densitometry examination with TBS assessment (Lunar Prodigy, TBS software 2.1.2). During 24-month follow-up, the frequency of low-trauma fractures was assessed and possible predictors of increased fracture risk were identified using product-moment correlation matrices.

RESULTS

Altogether 7 (11.9%) low-trauma fractures were observed. In the whole group, age (P = 0.047), T-score in proximal femur (P = 0.04), low vitamin D, low BMI (P = 0.03 for both), and higher FRAX for major osteoporotic fracture (P = 0.01) were connected with fractures, but in multi-variate analysis only BMI remained significantly negatively associated with fractures (P = 0.047). TBS and bone turnover markers failed to predict fractures. However, women with fractures had significantly lower serum phosphate (P = 0.03) and higher parathyroid hormone (P = 0.04). Parameters of hip structure analysis significantly correlated with FRAX, but not with fractures.

CONCLUSIONS

In a group of hemodialysis patients from one centre, T-score in proximal femur, low vitamin D, low BMI, and high FRAX for major osteoporotic fracture were associated with low-trauma fractures, however, in multi-variate analysis only low BMI remained a significant predictor of fracture risk.

The utility of FRAX® in predicting bone fractures in patients with chronic kidney disease on hemodialysis: a two-year prospective multicenter cohort study

We assessed the FRAX® method in 718 hemodialyzed patients in estimating increased risk of bone major and hip fractures. Over two prospective years, statistical analysis showed that FRAX® enables a better assessment of bone major fracture risk in these patients than any of its components and other risk factors considered in the analysis.

INTRODUCTION

Despite the generally increased risk of bone fractures among patients with end-stage renal disease, no prediction models for identifying individuals at particular risk have been developed to date. The goal of this prospective, multicenter observational study was to assess the usefulness of the FRAX® method in comparison to all its elements considered separately, selected factors associated with renal disease and the history of falls, in estimating increased risk of low-energy major bone and hip fractures in patients undergoing chronic hemodialysis.

METHODS

The study included a total of 1068 hemodialysis patients, who were followed for 2 years, and finally, 718 of them were analyzed. The risk analysis included the Polish version of the FRAX® calculator (without bone mineral density), dialysis vintage, mineral metabolism disorders (serum calcium, phosphate, and parathyroid hormone), and the number of falls during the last year before the study.

RESULTS

Over 2 years, low-energy 30 major bone fractures were diagnosed and 13 of hip fractures among them. Area under the curve for FRAX® was 0.76 (95% CI 0.69-0.84) for major fractures and 0.70 (95% CI 0.563-0.832) for hip fractures. The AUC for major bone fractures was significantly higher than for all elements of the FRAX® calculator. In logistic regression analysis FRAX® was the strongest independent risk factor of assessment of the major bone fracture risk.

CONCLUSIONS

FRAX® enables a better assessment of major bone fracture risk in ESRD patients undergoing hemodialysis than any of its components and other risk factors considered in the analysis.

Osteoporosis, bone mineral density and CKD-MBD complex (I): Diagnostic considerations

Osteoporosis (OP) and chronic kidney disease (CKD) independently influence bone and cardiovascular health. A considerable number of patients with CKD, especially those with stages 3a to 5D, have a significantly reduced bone mineral density leading to a high risk of fracture and a significant increase in associated morbidity and mortality. Independently of classic OP related to age and/or gender, the mechanical properties of bone are also affected by inherent risk factors for CKD ("uraemic OP"). In the first part of this review, we will analyse the general concepts regarding bone mineral density, OP and fractures, which have been largely undervalued until now by nephrologists due to the lack of evidence and diagnostic difficulties in the context of CKD. It has now been proven that a reduced bone mineral density is highly predictive of fracture risk in CKD patients, although it does not allow a distinction to be made between the causes which generate it (hyperparathyroidism, adynamic bone disease and/or senile osteoporosis, etc.). Therefore, in the second part, we will analyse the therapeutic indications in different CKD stages. In any case, the individual assessment of factors which represent a higher or lower risk of fracture, the quantification of this risk (i.e. using tools such as FRAX^®) and the potential indications for densitometry in patients with CKD could represent an important first step pending new clinical guidelines based on randomised studies which do not exclude CKD patients, all the while avoiding therapeutic nihilism in an area of growing importance.

Bone and mineral disorders in chronic kidney disease: implications for cardiovascular health and ageing in the general population

The patient with chronic kidney disease (CKD) represents an extreme model for arteriosclerosis, vascular calcification, and bone disorders, all of which are also associated with ageing in the general population. These pathological features are also relevant to other common chronic health disorders such as diabetes, and chronic inflammatory and cardiovascular diseases. Although management and interventions for these major risk factors are now incorporated into most public health guidelines (eg, smoking cessation and control of bodyweight and blood pressure, as well as glucose and cholesterol concentrations), some residual cardiovascular risk is not reduced by implementation of these interventions. CKD should be regarded as an atypical disease in which both traditional and novel cardiovascular risk factors have effects on outcomes. But CKD can also be viewed conceptually as an accelerator of traditional cardiovascular risk factors. Findings from research into mineral bone disorder associated with CKD (CKD-MBD) could help the medical community to better understand the vascular actions of certain molecules, such as phosphates, fibroblast growth factor 23, parathyroid hormone, sclerostin, or vitamin D and their relevance to the management of different pathologies in the general population. Importantly, these components, which are recognised in nephrology, could help to explain residual risk of cardiovascular events in the general population. Thus, achieving a better understanding of CKD-MBDs could provide substantial insight into future treatments for arteriosclerosis and osteoporosis, which are strongly associated with ageing and morbidity in the general population.

Bone turnover markers are associated with bone density, but not with fracture in end stage kidney disease: a cross-sectional study

BACKGROUND

Fracture risk is increased in chronic kidney disease (CKD), but assessment of bone fragility remains controversial in these patients. This study investigated the associations between bone turnover markers, bone mineral density (BMD), and prevalent fragility fracture in a cohort of kidney transplantation candidates.

METHODS

Volumetric BMD of spine and hip was measured by quantitative computed tomography. Parathyroid hormone (PTH), bone-specific alkaline phosphatase, procollagen type-1 N-terminal propeptide, tartrate resistant alkaline phosphatase, and C- and N-terminal telopeptides of type 1 collagen were analyzed from fasting morning blood samples. Fragility fractures included prevalent vertebral fractures and previous low-trauma clinical fractures.

RESULTS

The fracture prevalence was 18% in 157 adult kidney transplant candidates. Fractured patients had reduced BMD and Z-score at both spine and hip. Levels of bone turnover markers were significantly higher in patients on maintenance dialysis than in pre-dialysis patients; but did not differ between patients with and without fracture. There were strong, positive correlations between PTH and all bone turnover markers. PTH was negatively associated with Z-score at lumbar spine and total hip; in contrast, bone turnover markers were only negatively associated with total hip Z-score.

CONCLUSIONS

Bone turnover markers were negatively associated with bone density, but not associated with prevalent fracture in kidney transplantation candidates. The role of bone turnover markers in assessing bone fragility in CKD will require further investigation.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov with identifier NCT01344434 .

Renal Osteodystrophy or Kidney-Induced Osteoporosis?

PURPOSE OF REVIEW

Chronic kidney disease (CKD) affects nearly 10% of the population. The incidence of fractures in population studies demonstrate an increase with worsening stages of kidney disease suggesting specific CKD related causes of fracture.

RECENT FINDINGS

The increase in fractures with CKD most likely represents disordered bone quality due to the abnormal bone remodeling from renal osteodystrophy. There is also an increase in fractures with age in patients with CKD, suggesting that patients with CKD also have many fracture risk factors common to patients without known CKD. Osteoporosis is defined by the National Institutes of Health as "A skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Bone strength reflects the integration of two main features: bone quantity and bone quality." Thus, CKD-related fractures can be considered a type of osteoporosis-where the bone quality is additionally impaired above that of age/hormonal-related osteoporosis. Perhaps using the term CKD-induced osteoporosis, similar to steroid-induced osteoporosis, will allow patients with CKD to be studied in trials investigating therapeutic agents. In this series, we will examine how CKD-induced osteoporosis may be diagnosed and treated.

Evaluation of fracture risk in chronic kidney disease

Chronic kidney disease (CKD) is associated with mineral and bone disorders (MBD) that are now considered as a syndrome. Bone fragility and a four to tenfold increased rate of skeletal fractures are often reported in CKD patients. The evaluation of the risk of these fractures in CKD patients should explore the same risk factors identified for the general population including low body weight, menopause, personal and familial history of osteoporosis, chronic inflammatory diseases, and corticosteroid therapy. The aim of this article is to provide a critical review of the tools used for the evaluation of bone loss and the risk of fracture in CKD patients, ranging from the measurement of bone mineral density (BMD), fracture risk assessment (Frax™), quantitative computed tomography (QCT), high-resolution peripheral quantitative computed tomography (HRpQTC), to circulating biomarkers of bone metabolism including vitamin D, parathyroid hormone (PTH), bone-specific alkaline phosphatase, osteocalcin, and some collagen type 1-related molecules indicators of bone remodeling.

Evaluation of three risk assessment tools in discriminating fracture status among Chinese patients undergoing hemodialysis

We evaluated three risk assessment tools, including bone mineral density (BMD) measurement by dual energy X-ray absorptiometry (DXA), osteoporosis self-assessment tool for Asians (OSTA), and fracture risk assessment tool (FRAX), for the prediction of fracture status among Chinese patients undergoing hemodialysis. All of the three assessment tools have a reasonable capability in discriminating fractures.

INTRODUCTION

Fractures are common in hemodialysis patients however insufficiently assessed. Our study aimed to assess the ability of three widely used tools [BMD, OSTA, and FRAX] to discriminate fracture status in patients with renal failure undergoing hemodialysis.

METHODS

We enrolled 136 hemodialysis patients in a tertiary teaching hospital setting. BMD was measured using DXA at the lumbar spine and the hip region. OSTA was calculated from weight and age. FRAX score was calculated based upon online availability. Discriminative abilities of BMD, OSTA, and FRAX in fracture status were analyzed by receiver operator characteristic (ROC) curves.

RESULTS

There were total 16 fractures (11.76 %) identified in 136 hemodialysis patients. BMD at any site (lumbar spine L1-L4, femoral neck, and total hip) was independently associated with fracture. Areas under the curves (AUC) of BMD (lumbar spine L1-L4, femoral neck, total hip), OSTA, FRAX1 (non-BMD model), and FRAX2 (BMD model) were 0.669 (95 % CI 0.583, 0.747), 0.708 ( 95 % CI 0.624, 0.783), 0.736 (95 % CI 0.654, 0.808), 0.686 (95 % CI 0.601, 0.763), 0.715 (95 % CI 0.631, 0.789), and 0.697 (95 % CI 0.613, 0.773), respectively. The differences of their performance were not significant.

CONCLUSIONS

All of the three risk assessment tools had the ability to discriminate fracture status among hemodialysis patients; FRAX BMD model did not improve the discriminative ability of BMD or FRAX non-BMD model alone.

A systematic review of intervention thresholds based on FRAX : A report prepared for the National Osteoporosis Guideline Group and the International Osteoporosis Foundation

This systematic review identified assessment guidelines for osteoporosis that incorporate FRAX. The rationale for intervention thresholds is given in a minority of papers. Intervention thresholds (fixed or age-dependent) need to be country-specific.

INTRODUCTION

In most assessment guidelines, treatment for osteoporosis is recommended in individuals with prior fragility fractures, especially fractures at spine and hip. However, for those without prior fractures, the intervention thresholds can be derived using different methods. The aim of this report was to undertake a systematic review of the available information on the use of FRAX® in assessment guidelines, in particular the setting of thresholds and their validation.

METHODS

We identified 120 guidelines or academic papers that incorporated FRAX of which 38 provided no clear statement on how the fracture probabilities derived are to be used in decision-making in clinical practice. The remainder recommended a fixed intervention threshold (n = 58), most commonly as a component of more complex guidance (e.g. bone mineral density (BMD) thresholds) or an age-dependent threshold (n = 22). Two guidelines have adopted both age-dependent and fixed thresholds.

RESULTS

Fixed probability thresholds have ranged from 4 to 20 % for a major fracture and 1.3-5 % for hip fracture. More than one half (39) of the 58 publications identified utilised a threshold probability of 20 % for a major osteoporotic fracture, many of which also mention a hip fracture probability of 3 % as an alternative intervention threshold. In nearly all instances, no rationale is provided other than that this was the threshold used by the National Osteoporosis Foundation of the USA. Where undertaken, fixed probability thresholds have been determined from tests of discrimination (Hong Kong), health economic assessment (USA, Switzerland), to match the prevalence of osteoporosis (China) or to align with pre-existing guidelines or reimbursement criteria (Japan, Poland). Age-dependent intervention thresholds, first developed by the National Osteoporosis Guideline Group (NOGG), are based on the rationale that if a woman with a prior fragility fracture is eligible for treatment, then, at any given age, a man or woman with the same fracture probability but in the absence of a previous fracture (i.e. at the 'fracture threshold') should also be eligible. Under current NOGG guidelines, based on age-dependent probability thresholds, inequalities in access to therapy arise especially at older ages (≥70 years) depending on the presence or absence of a prior fracture. An alternative threshold using a hybrid model reduces this disparity.

CONCLUSION

The use of FRAX (fixed or age-dependent thresholds) as the gateway to assessment identifies individuals at high risk more effectively than the use of BMD. However, the setting of intervention thresholds needs to be country-specific.

Trabecular Bone Score and Incident Fragility Fracture Risk in Adults with Reduced Kidney Function

BACKGROUND AND OBJECTIVES

Trabecular bone score is a gray-level textural measure obtained from dual energy x-ray absorptiometry lumbar spine images that provides information independent of areal bone mineral density. The association between trabecular bone score and incident fractures in adults with reduced kidney function and whether this association differs from that of adults with normal kidney function are unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We included 1426 participants ages ≥40 years old (mean age of 67 years) in the community-based Canadian Multicentre Osteoporosis Study. We stratified participants at cohort entry (2005-2008) by eGFR (eGFR<60 ml/min per 1.73 m2 [n=199; 72.4% stage 3a, 25.1% stage 3b, and 2.5% stage 4] versus ≥60 ml/min per 1.73 m2 [n=1227]). Trabecular bone score was obtained from lumbar spine (L1-L4) dual energy x-ray absorptiometry images, with a lower trabecular bone score representing worse bone structure. Over an average of 4.7 years follow-up (maximum follow-up of 5 years), we documented incident fragility (low-trauma) fracture events (excluding craniofacial, foot, and hand sites). We used a modified Kaplan-Meier estimator to determine the 5-year probability of fracture. Cox proportional hazard regression per SD lower trabecular bone score expressed the gradient of fracture risk.

RESULTS

Individuals with an eGFR<60 ml/min per 1.73 m2 who had a trabecular bone score value below the median (<1.277) had a significantly higher 5-year fracture probability than those above the median (18.1% versus 6.2%; P=0.01). The association between trabecular bone score and fracture was independent of bone mineral density and other clinical risk factors in adults with reduced and normal kidney function (adjusted hazard ratio per SD lower trabecular bone score: eGFR<60 ml/min per 1.73 m2: adjusted hazard ratio, 1.62; 95% confidence interval, 1.04 to 2.51; eGFR≥60 ml/min per 1.73 m2: adjusted hazard ratio, 1.44; 95% confidence interval, 1.13 to 1.83).

CONCLUSIONS

Lower lumbar spine trabecular bone score is independently associated with a higher fracture risk in adults with reduced kidney function. Additional study is needed to examine the association between trabecular bone score and fractures in individuals with diagnosed CKD-mineral and bone disorder.

An update on bone imaging and markers in chronic kidney disease

Bone disorders in chronic kidney disease (CKD) are associated with heightened risks of fractures, vascular calcification, poor quality of life and mortality compared to the general population. However, diagnosis and management of these disorders in CKD are complex and appreciably limited by current diagnostic modalities. Areas covered: Bone histomorphometry remains the gold standard for diagnosis but is not widely utilised and lacks feasibility as a monitoring tool. In practice, non-invasive imaging and biochemical markers are preferred to guide therapeutic decisions. Expert commentary: This review aims to summarize the risk factors for, and spectrum of bone disease in CKD, as well as appraise the clinical utility of dual energy X-ray densitometry, peripheral quantitative computed tomography, high-resolution peripheral quantitative computed tomography, and bone turnover markers.

Micro-CT in the Assessment of Pediatric Renal Osteodystrophy by Bone Histomorphometry

BACKGROUND AND OBJECTIVES

Computed tomography (CT) measurements can distinguish between cortical and trabecular bone density in vivo. High-resolution CTs assess both bone volume and density in the same compartment, thus potentially yielding information regarding bone mineralization as well. The relationship between bone histomorphometric parameters of skeletal mineralization and bone density from microcomputed tomography (μCT) measurements of bone cores from patients on dialysis has not been assessed.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Bone cores from 68 patients with ESRD (age =13.9±0.5 years old; 50% men) and 14 controls (age =15.3±3.8 years old; 50% men) obtained as part of research protocols between 1983 and 2006 were analyzed by bone histomorphometry and μCT.

RESULTS

Bone histomorphometric diagnoses in the patients were normal to high bone turnover in 76%, adynamic bone in 13%, and osteomalacia in 11%. Bone formation rate did not correlate with any μCT determinations. Bone volume measurements were highly correlated between bone histomorphometry and μCT (bone volume/tissue volume between the two techniques: r=0.70; P<0.001, trabecular thickness and trabecular separation: r=0.71; P<0.001, and r=0.56; P<0.001, respectively). Osteoid accumulation as determined by bone histomorphometry correlated inversely with bone mineral density as assessed by μCT (osteoid thickness: r=-0.32; P=0.01 and osteoid volume: r=-0.28; P=0.05). By multivariable analysis, the combination of bone mineral density and bone volume (as assessed by μCT) along with parathyroid hormone and calcium levels accounted for 38% of the variability in osteoid volume (by histomorphometry).

CONCLUSIONS

Measures of bone volume can be accurately assessed with μCT. Bone mineral density is lower in patients with excessive osteoid accumulation and higher in patients with adynamic, well mineralized bone. Thus, bone mineralization may be accurately assessed by μCT of bone biopsy cores. Additional studies are warranted to define the value of high-resolution CT in the prediction of bone mineralization in vivo.

The FRAX ® as a predictor of mortality in Japanese incident hemodialysis patients: an observational, follow-up study

The World Health Organization Fracture Risk Assessment Tool (FRAX(®)) was recently developed to estimate the 10-year absolute risk of osteoporotic fracture among the general population. However, the evidence for its use in chronic kidney disease patients has been lacking, and the association between the FRAX(®) and mortality is unknown. Therefore, a hospital-based, prospective, cohort study was conducted to evaluate the predictive ability of the FRAX(®) for mortality in hemodialysis patients. A total of 252 patients who had been started on maintenance hemodialysis, 171 men and 81 women, with a mean age of 67 ± 14 years, was studied. The endpoint was defined as all-cause death. The Cox proportional hazards model was used to calculate hazard ratios and 95 % confidence intervals. During the mean follow-up period of 3.4 ± 2.7 years, 61 deaths occurred. The median (interquartile range) of the FRAX(®) for major osteoporotic fracture was 6.9 (4.6-12.0) % in men and 19.0 (7.6-33.0) % in women. Cumulative survival rates at 5 years after starting dialysis, with the FRAX(®) levels above and below the median, were 51.9 and 87.9 %, respectively, in men and 67.4 and 83.7 %, respectively, in women. Overall, in men, the multivariate Cox regression analyses revealed that the log-transformed FRAX(®) remained an independent predictor of death after adjusting by confounding variables. However, in women, the significant association between the FRAX(®) value and the outcome was eliminated if age was put into these models. Among Japanese hemodialysis patients, the FRAX(®) seems to be useful for predicting death, especially in men.

Bone imaging and fracture risk assessment in kidney disease

Fractures are more common and are associated with greater morbidity and morality in patients with kidney disease than in members of the general population. Thus, it is troubling that in chronic kidney disease (CKD) patients there has been a paradoxical increase in fracture rates over the past 20 years compared to the general population. Increased fracture incidence in CKD patients may be driven in part by the lack of screening for fracture risk. In the general population, dual energy X-ray absorptiometry (DXA) is the clinical standard to stratify fracture risk, and its use has contributed to decreases in fracture incidence. In contrast, in CKD, fracture risk screening with DXA has been uncommon due to its unclear efficacy in predicting fracture and its inability to predict type of renal osteodystrophy. Recently, several prospective studies conducted in patients across the spectrum of kidney disease have demonstrated that bone mineral density measured by DXA predicts future fracture risk and that clinically relevant information regarding fracture risk is provided by application of the World Health Organization cutoffs for osteopenia and osteoporosis to DXA measures. Furthermore, novel high-resolution imaging tools, such as high-resolution peripheral quantitative computed tomography (HR-pQCT), have been used to elucidate the effects of kidney disease on cortical and trabecular microarchitecture and bone strength and to identify potential targets for strategies that protect against fractures. This review will discuss the updated epidemiology of fractures in CKD, fracture risk screening by DXA, and the utility of state-of-the art imaging methods to uncover the effects of kidney disease on the skeleton.

Comparison of fracture risk prediction among individuals with reduced and normal kidney function

BACKGROUND AND OBJECTIVES

The Fracture Risk Assessment Tool (FRAX) is widely used to predict the 10-year probability of fracture; however, the clinical utility of FRAX in CKD is unknown. This study assessed the predictive ability of FRAX in individuals with reduced kidney function compared with individuals with normal kidney function.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The discrimination and calibration (defined as the agreement between observed and predicted values) of FRAX were examined using data from the Canadian Multicentre Osteoporosis Study (CaMos). This study included individuals aged ≥40 years with an eGFR value at year 10 of CaMos (defined as baseline). The cohort was stratified by kidney function at baseline (eGFR<60 ml/min per 1.73 m(2) [72.2% stage 3a, 23.8% stage 3b, and 4.0% stage 4/5] versus ≥60 ml/min per 1.73 m(2)) and followed individuals for a mean of 4.8 years for an incident major osteoporotic fracture (clinical spine, hip, forearm/wrist, or humerus).

RESULTS

There were 320 individuals with an eGFR<60 ml/min per 1.73 m(2) and 1787 with an eGFR≥60 ml/min per 1.73 m(2). The mean age was 67±10 years and 71% were women. The 5-year observed major osteoporotic fracture risk was 5.3% (95% confidence interval [95% CI], 3.3% to 8.6%) in individuals with an eGFR<60 ml/min per 1.73 m(2), which was comparable to the FRAX-predicted fracture risk (6.4% with bone mineral density; 8.2% without bone mineral density). A statistically significant difference was not observed in the area under the curve values for FRAX in individuals with an eGFR<60 ml/min per 1.73 m(2) versus ≥60 ml/min per 1.73 m(2) (0.69 [95% CI, 0.54 to 0.83] versus 0.76 [95% CI, 0.70 to 0.82]; P=0.38).

CONCLUSIONS

This study showed that FRAX was able to predict major osteoporotic fractures in individuals with reduced kidney function; further study is needed before FRAX should be routinely used in individuals with reduced kidney function.