Chronic hemodialysis is associated with lower trabecular bone score, independent of bone mineral density: a case-control study

Comprehensive Evaluation of Bone Health Among Kidney Transplant Recipients - A Prospective, Single Center, Observational Cohort Study from India

BACKGROUND

There is a paucity of studies describing trabecular bone score (TBS) and bone mineral density (BMD) in kidney transplant (KT) recipients from developing countries.

STUDY SETTING

This prospective observational study, from a tertiary teaching hospital in India assessed clinical, biochemical parameters including bone turnover markers and dual-energy X-ray absorptiometry (DXA) for BMD/TBS, hip structural analysis (HSA) and vertebral fracture assessment (VFA) at pre-KT, 3 months and 12 months post-KT.

RESULTS

A total of 53 KT recipients (90.6% living related) were recruited from August 2019 to March 2020 and followed till 1-year post-KT. The mean age was 33.9±10.4 years, 71.7% were males, and 11.5% had a history of pre-KT steroid use. Baseline fractures pre-KT as assessed by VFA were seen in 4 patients (7.5%). Mean BMD at spine and femoral neck and HSA variables at narrow neck and femoral shaft continued to decline till 3 months, but stabilised and reached pre-KT values 12 months post-KT. However, TBS and bone turn over markers continued to decline till 12 months post-KT (p value <0.001). New onset vertebral fractures were seen in 2(3.7%) and 1 patient (2.3%) at 3- and 12-months post-KT respectively. Pre-KT BMD significantly influenced bone health at 12 months post-KT, with patients in each quartile maintaining a similar trajectory over the follow up period (p < 0.001).

CONCLUSION

Despite significant improvement in kidney function following transplant, TBS and BMD of the spine significantly decreased mainly in the early post-KT period suggesting the effect of immunosuppressants on the bone. Strategies to improve bone health in KT patients are warranted.

Trabecular Bone Score as a Marker of Skeletal Fragility Across the Spectrum of Chronic Kidney Disease: A Systematic Review and Meta-analysis

CONTEXT

The impairment of bone microarchitecture is a key determinant of skeletal fragility in patients with chronic kidney disease (CKD). The trabecular bone score (TBS) has been developed as a reliable noninvasive index of bone quality. However, its utility in this setting is still debated.

OBJECTIVE

The aim of this systematic review and meta-analysis was to summarize the available evidence about TBS as a marker of skeletal fragility across the spectrum of CKD.

METHODS

PubMed/Medline, EMBASE, and Cochrane Library databases were systematically searched until July 2023 for studies reporting data about TBS in patients with CKD. Effect sizes were pooled through a random-effect model.

RESULTS

Compared to controls, lower TBS values were observed in CKD patients not on dialysis (-0.057, 95%CI:[-0.090, -0.024], P < .01), in dialysis patients (-0.106, 95%CI:[-0.141, -0.070], P < .01), and in kidney transplant recipients (KTRs) (-0.058, 95%CI:[-0.103, -0.012], P = .01). With respect to fracture risk, TBS was able to predict incident fractures in nondialysis patients at unadjusted analyses (hazard ratio [HR] per SD decrease: 1.45, 95%CI:[1.05, 2.00], P = .02), though only a nonsignificant trend was maintained when fully adjusting the model for FRAX® (HR = 1.26, 95%CI:[0.88, 1.80], P = .21). Dialysis patients with prevalent fractures had lower TBS values compared to unfractured ones (-0.070, 95% CI:[-0.111, -0.028], P < .01). Some studies supported a correlation between TBS and fracture risk in KTRs, but results could not be pooled due to the lack of sufficient data.

CONCLUSION

CKD patients are characterized by an impairment of bone microarchitecture, as demonstrated by lower TBS values, across the whole spectrum of kidney disease. TBS can also be helpful in the discrimination of fracture risk, with lower values being correlated with a higher risk of prevalent and incident fractures.

The relationship between serum pro-B type natriuretic peptide level and bone mineral density in peritoneal dialysis patients

We aimed to evaluate the relationship between serum N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) and lumbar bone mineral density (BMD) in peritoneal dialysis (PD) patients. Fasting blood samples were obtained from 46 PD patients. BMD was measured by dual-energy X-ray absorptiometry of the lumbar vertebrae (L1-L4). Circulating serum NT-pro-BNP levels were measured using commercial kits compatible with the Roche Cobas e 601 immunoassay device. Forty-six patients were included in our study. Increased age, low body mass index (BMI), and high-serum NT-pro-BNP are significantly associated with decreased BMD. The results show a statistically positive correlation between lumbar T-score values and BMI (r = 0.456; P = .001), while lumbar T-score values and PTH (rho = -0.336; P = .022) and log-NT-pro-BNP. There is a statistically negative correlation between BNP (rho = -0.355; P = .015). The lumbar T-score value decreases by 0.800 units when log-NT-pro-BNP increases by 1 unit and increases by 0.323 units when BMI increases by 1 unit. The established model is statistically significant (F = 6.190; P < .001). Our study in PD patients showed that serum NT-pro-BNP level was negatively correlated and BMI was positively correlated with lumbar BMD.

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.

Usefulness of the trabecular bone score in maintenance dialysis patients : A single center observational study

Background

The number of dialysis patients is steadily increasing. Associated comorbidities include impaired bone and mineral metabolism, termed chronic kidney disease-mineral and bone disorder (CKD-MBD), leading to a high fracture risk, increased morbidity and mortality and impaired quality of life. While the bone density is assessed with dual-energy X‑ray absorptiometry (DXA), the trabecular bone score (TBS) captures the image texture as a potential index of skeletal microarchitecture. The aim of this study was to evaluate the clinical relevance of DXA and TBS in dialysis patients with and without prevalent fractures.

Methods

Bone disorders were evaluated in 82 dialysis patients (37% female) at the University Hospital of Graz, Austria, by DXA including the assessment of the TBS based on a patient interview and the local routine patient database software. The patient cohort was stratified by having sustained a fragility fracture in the past or not. Descriptive statistics, t‑tests for continuous variables and χ²-tests for nominal variables including results of DXA and TBS were performed to compare these groups considering the dialysis modality and duration as well as the number of kidney transplantations.

Results

Of the 82 patients, 32 (39%) had a positive history of fractures. There was a significant association between dialysis duration and fracture prevalence (p < 0.05) as well as musculoskeletal pain (p < 0.01). No significant correlation between DXA/TBS parameters and musculoskeletal pain could be established. The DXA scores did not correlate with fracture prevalence with the exception of DXA radius measurements; however, fracture prevalence significantly correlated inversely with TBS (p < 0.001).

Conclusion

The use of DXA has a limited role in fracture prediction in dialysis patients; however, the TBS seems to add information as an additional tool for fracture risk estimation in this patient population.

Utility of Trabecular Bone Score (TBS) in Bone Quality and Fracture Risk Assessment in Patients on Maintenance Dialysis

Maintenance dialysis is associated with almost universal changes in bone metabolism collectively known as chronic kidney disease—mineral and bone disorder (CKD-MBD). These are accompanied in various proportions by bone loss and altered bone quality that led to an increased risk of fracture. Osteoporosis, age-related or postmenopausal, a condition that often coexists with CKD, is also a leading cause of fracture. Dual-energy X-ray densitometry (DXA) is the main tool for assessing the bone quantity and bone loss and the associated fracture risk. It has been validated in both CKD-MBD and osteoporosis. Trabecular bone score (TBS) is a DXA-derived algorithm for the evaluation of bone microarchitecture, and its clinical value has been repeatedly demonstrated in large cohorts of osteoporotic patients. However, its utility in patients on maintenance dialysis has not been conclusively shown. Published studies showed a lower TBS score and implicitly an altered bone microarchitecture in patients on maintenance dialysis, even after adjusting for various variables. Moreover, FRAX-based fracture risk is higher after adjusting for TBS, showing promise on an algorithm better estimating the clinical fracture risk in dialysis patients. However, TBS has not been demonstrated to independently predict clinical fractures in prospective studies on dialysis patients. Also, aortic calcifications and altered fluid balance could significantly affect TBS score and could hamper the widespread clinical use in patients on maintenance dialysis. In this mini-review, we focus on the benefits and pitfalls of TBS in the management of CKD-MBD and fracture risk assessment in patients on maintenance dialysis.

Is dual-energy absorptiometry accurate in the assessment of bone status of patients with chronic kidney disease?

Several patients with chronic kidney disease (CKD) have deteriorated bone status. Estimation of bone status using DXA has limitations especially in patients with CKD accompanying aortic calcifications. Quantitative CT and the trabecular bone score could be more accurate methods to estimate bone status for patients with CKD and vascular calcifications.

INTRODUCTION

It remains unclear whether dual-energy absorptiometry (DXA) is appropriate for the assessment of bone status in patients with chronic kidney disease (CKD), a disease that impacts bone health. The aims of this study were to compare DXA and central quantitative computed tomography (cQCT) and to evaluate bone status in patients with pre-dialysis CKD.

METHODS

This retrospective study included 363 healthy control subjects whose bone mineral density (BMD) was evaluated with DXA and 117 CKD patients whose BMD was evaluated using both cQCT and DXA. Diagnostic discordance was assessed between the lumbar spine (LS) and femur neck (FN) from DXA or between two modalities. The trabecular bone score (TBS) was extracted from DXA images. The volume of abdominal aortic calcification (AAC) was calculated using CT images from cQCT.

RESULTS

Using LS DXA T-score, osteoporosis was less common in the CKD group than in controls. Patients with normal LS BMD using DXA were reclassified into osteopenia or osteoporosis using cQCT in CKD patients. Among discordant subjects between FN and LS in DXA, a higher BMD of LS was more common in CKD patients than in controls. CKD patients had lower TBS than controls despite having the same diagnosis using DXA. AAC volume negatively correlated with BMD from cQCT and with TBS but not with BMD from DXA.

CONCLUSIONS

TBS and cQCT could accurately assess bone status in CKD patients since DXA may overestimate LS BMD, likely due to an increased AAC volume.

Bone Quality in CKD Patients: Current Concepts and Future Directions - Part I

BACKGROUND

There is ample evidence that patients with CKD have an increased risk of osteoporotic fractures. Bone fragility is not only influenced by low bone volume and mass but also by poor microarchitecture and tissue quality. More emphasis has been given to the quantitative rather than qualitative assessment of bone health, both in general population and CKD patients. Although bone mineral density (BMD) is a very useful clinical tool in assessing bone strength, it may underestimate the fracture risk in CKD patients. Serum and urinary bone biomarkers have been found to be reflective of bone activities and predictive of fractures independently of BMD in CKD patients. Bone quality and fracture risk in CKD patients can be better assessed by utilizing new technologies such as trabecular bone score and high-resolution imaging studies. Additionally, invasive assessments such as bone histology and micro-indentation are useful counterparts in the evaluation of bone quality.

SUMMARY

A precise diagnosis of the underlying skeletal abnormalities in CKD patients is crucial to prevent further bone loss and fractures. We must consider bone quantity and quality abnormalities for management of CKD patients. Here in this part I, we are focusing on advances in bone quality diagnostics that are expected to help in proper understanding of the bone health in CKD patients.

KEY MESSAGES

Assessment of bone quality and quantity in CKD patients is essential. Both noninvasive and invasive techniques for the assessment of bone quality are available.

The Non-invasive Diagnosis of Bone Disorders in CKD

Abnormal bone metabolism is an integral part of the chronic kidney disease-mineral bone disorder (CKD-MBD). For several reasons, the difficult bone compartment was neglected for some time, but there has been renewed interest as a result of the conception of bone as a new endocrine organ, the increasing recognition of the cross-talk between bone and vessels, and, especially, the very high risk of osteoporotic fractures (and associated mortality) demonstrated in patients with CKD. Therefore, it has been acknowledged in different guidelines that action is needed in respect of fracture risk assessment and the diagnosis and treatment of osteoporosis in the context of CKD and CKD-MBD, even beyond renal osteodystrophy. These updated guidelines clearly underline the need to improve a non-invasive approach to these bone disorders in order to guide treatment decisions aimed at not only controlling CKD-MBD but also decreasing the risk of fracture. In this report, we review the current role of the most often clinically used or promising biochemical circulating biomarkers such as parathyroid hormone, alkaline phosphatases, and other biochemical markers of bone activity as alternatives to some aspects of bone histomorphometry. We also mention the potential role of classic and new imaging techniques for CKD patients. Information on many aspects is still scarce and heterogeneous, but many of us consider that it is indeed time for action, recognizing our definitely limited ability to base certain treatment decisions only on our current non-comprehensive knowledge.

Expression of Circulating MicroRNAs Linked to Bone Metabolism in Chronic Kidney Disease-Mineral and Bone Disorder

The pathophysiology of chronic kidney disease-mineral and bone disorder (CKD-MBD) is complex and multifactorial. Recent studies have identified a link between microRNAs (miRNAs) and bone loss. In this study, we investigated the expression of miRNAs in CKD-MBD. In this case-control study, we included thirty patients with CKD-MBD (cases) and 30 age- and gender-matched healthy individuals (controls). Bone mineral density (BMD) and trabecular bone score (TBS) evaluation was performed with dual X-ray absorptiometry. The selected panel of miRNAs included: hsa-miRNA-21-5p; hsa-miRNA-23a-3p; hsa-miRNA-24-2-5p; hsa-miRNA-26a-5p; hsa-miRNA-29a-3; hsa-miRNA-124-3p; hsa-miRNA-2861. The majority of cases had low BMD values. The relative expression of miRNA-21-5p was 15 times lower [fold regulation (FR): -14.7 ± 8.1, p = 0.034), miRNA-124-3p, 6 times lower (FR: -5.9 ± 4, p = 0.005), and miRNA-23a-3p, 4 times lower (FR: -3.8 ± 2.0, p = 0.036) in cases compared to controls. MiRNA-23a-3p was significantly and inversely correlated with TBS, adjusted for calcium metabolism and BMD values (beta = -0.221, p = 0.003, 95% CI -0.360, -0,081) in cases. In a receiver operating characteristic (ROC) analysis, expression of miRNA-124-3p demonstrated 78% sensitivity and 83% specificity in identifying CKD patents with osteoporosis. Serum expression of miRNAs related to osteoblasts (miRNA-23a-3p) and osteoclasts (miRNA-21-5p, miRNA-124-3p) is significantly altered in patients with CKD-MBD.

Trabecular bone score may indicate chronic kidney disease-mineral and bone disorder (CKD-MBD) phenotypes in hemodialysis patients: a prospective observational study

BACKGROUND

In the general population, the trabecular bone score (TBS) represents the bone microarchitecture and predicts fracture risk independent of bone mineral density (BMD). A few studies reported that TBS is significantly reduced in dialysis patients. Chronic kidney disease-mineral and bone disorder (CKD-MBD) are accompanied by increased fracture risk, cardiovascular morbidity, and mortality. We investigated whether TBS is associated with comorbidity related to CKD-MBD or frailty in hemodialysis patients.

METHODS

In this prospective observational study, TBS was obtained using the TBS iNsight software program (Med-Imaps) with BMD dual energy x-ray absorptiometry (DXA) images (L1-L4) from prevalent hemodialysis patients. A Tilburg frailty indicator was used to evaluate frailty, and hand grip strength and bio-impedance (InBody) were measured. A patient-generated subjective global assessment (PG-SGA) was used for nutritional assessment. The history of cardiovascular events (CVE) and demographic, clinical, laboratory, and biomarker data were collated. We then followed up patients for the occurrence of CKD-MBD related complications.

RESULTS

We enrolled 57 patients in total. The mean age was 56.8 ± 15.9 years (50.9% female). Prevalence of Diabetes mellitus (DM) was 40.4% and CVE was 36.8%. Mean TBS was 1.44 ± 0.10. TBS significantly reduced in the CVE group (1.38 ± 0.08 vs. 1.48 ± 0.10, p <  0.001). Multivariable regression analysis was conducted adjusting for age, sex, dialysis vintage, DM, CVE, albumin, intact parathyroid hormone, fibroblast growth factor 23, handgrip strength, and phosphate binder dose. Age (ß = - 0.030; p = 0.001) and CVE (ß = - 0.055; p = 0.024) were significant predictors of TBS. During the follow up period after TBS measurements (about 20 months), four deaths, seven incident fractures, and six new onset CVE were recorded. Lower TBS was associated with mortality (p = 0.049) or new onset fracture (p = 0.007, by log-rank test).

CONCLUSION

Lower TBS was independently associated with increased age and CVE prevalence in hemodialysis patients. Mortality and fracture incidence were significantly higher in patients with lower TBS values. These findings suggest that TBS may indicate a phenotype of frailty and also a CKD-MBD phenotype reciprocal to CVE.

Bone turnover correlates with bone quantity but not bone microarchitecture in chronic hemodialysis

INTRODUCTION

In chronic hemodialysis, high-turnover bone disease was associated with decreased bone mineral density (BMD), poor bone quality (chemical and structural), and increased fracture risk. Our aim was to correlate bone turnover markers (BTMs) with bone microarchitecture measured by trabecular bone score (TBS) before and after correction for BMD.

MATERIALS AND METHODS

We measured lumbar spine (LS), femoral neck, and 1/3 radius BMD and LS TBS by dual X-ray absorptiometry in 81 patients on permanent hemodialysis. Bone turnover was assessed using serum parathyroid hormone, osteocalcin, C-terminal crosslaps of type 1 collagen, procollagen 1 N-terminal propeptide (P1NP), and alkaline phosphatase (ALP). No patient had any partial or total parathyroidectomy and no previous or current treatment with anti-osteoporotic drugs.

RESULTS

All BTMs correlated significantly with each other. Univariate regressions showed significant negative correlations between BTMs and BMD (best r = - 0.53, between P1NP and 1/3 radius Z-score) or BTMs and TBS (best r = - 0.27, p < 0.05 between ALP and TBS T-score). TBS correlated significantly with BMD at all three sites (best r = 0.5, between LS BMD and TBS T-score). Multivariate regression showed that TBS, crude or adjusted, correlated with LS BMD. No model retained any of the BTMs as independent variables due to the better prediction of BMD and multicollinearity.

CONCLUSION

We showed a progressively impaired bone microarchitecture with increasing bone turnover in chronic hemodialysis. However, this correlation is no longer present when controlling for bone mass. This suggests that impaired bone microarchitecture and increased fracture risk are dependent upon factors other than high bone turnover.