The Use of Fibroblast Growth Factor 23 Testing in Patients with Kidney Disease

The emergence of fibroblast growth factor 23 as a potentially modifiable risk factor in CKD has led to growing interest in its measurement as a tool to assess patient risk and target therapy. This review discusses the analytical and clinical challenges faced in translating fibroblast growth factor 23 testing into routine practice. As for other bone mineral markers, agreement between commercial fibroblast growth factor 23 assays is poor, mainly because of differences in calibration, but also, these differences reflect the variable detection of hormone fragments. Direct comparison of readout from different assays is consequently limited and likely hampers setting uniform fibroblast growth factor 23–directed targets. Efforts are needed to standardize assay output to enhance clinical use. Fibroblast growth factor 23 is robustly associated with cardiovascular and renal outcomes in patients with CKD and adds value to risk assessments based on conventional risk factors. Compared with most other mineral markers, fibroblast growth factor 23 shows better intraindividual temporal stability, with minimal diurnal and week-to-week variability, but substantial interindividual variation, maximizing discriminative power for risk stratification. Conventional therapeutic interventions for the CKD–mineral bone disorder, such as dietary phosphate restriction and use of oral phosphate binders or calcimimetics, are associated with variable efficacy at modulating circulating fibroblast growth factor 23 concentrations, like they are for other mineral metabolites. Dual therapy with dietary phosphate restriction and noncalcium-based binder use achieves the most consistent fibroblast growth factor 23–lowering effect and seems best monitored using an intact assay. Additional studies are needed to evaluate whether strategies aimed at reducing levels or antagonizing its action have beneficial effects on clinical outcomes in CKD patients. Moreover, a better understanding of the mechanisms driving fibroblast growth factor 23 elevations in CKD is needed to inform the use of therapeutic interventions targeting fibroblast growth factor 23 excess. This evidence must be forthcoming to support the use of fibroblast growth factor 23 measurement and fibroblast growth factor 23–directed therapy in the clinic.     

Comparison of Fracture Prediction Tools in Individuals Without and With Early Chronic Kidney Disease: A Population-Based Analysis of CARTaGENE

Whether fracture prediction tools developed for the management of osteoporosis can be used in chronic kidney disease (CKD) is poorly known. We aimed to compare the performance of fracture prediction tools in non-CKD and CKD. We analyzed CARTaGENE, a population-based survey of 40-year-old to 69-year-old individuals recruited between 2009 and 2010. Renal function was assessed using baseline creatinine and categorized according to Kidney Disease Improving Global Outcomes (KDIGO) guidelines (non-CKD, stage 2, stage 3). Individuals without creatinine measurements or with advanced CKD (stage 4 or 5; prevalence <0.25%) were excluded. Predicted 5-year fracture probabilities (using Fracture Risk Assessment Tool [FRAX], QFracture, and Garvan) were computed at baseline. Fracture incidence (major fracture [MOF] or any fracture) was evaluated in administrative databases from recruitment to March 2016. Discrimination (hazard ratios [HRs] per standard deviation [SD] increase in Cox models; c-statistics) and calibration (standardized incidence ratios [SIRs] before and after recalibration) were assessed in each CKD strata. We included 19,393 individuals (9522 non-CKD; 9114 stage 2; 757 stage 3). A total of 830 patients had any fracture during follow-up, including 352 MOF. FRAX (HR = 1.89 [1.63–2.20] non-CKD; 1.64 [1.41–1.91] stage 2; 1.76 [1.10–2.82] stage 3) and QFracture (HR = 1.90 [1.62–2.22] non-CKD; 1.57 [1.35–1.82] stage 2; 1.86 [1.19–2.91] stage 3) discriminated MOF similarly in non-CKD and CKD. In contrast, the discrimination of Garvan for any fracture tended to be lower in CKD stage 3 compared to non-CKD and CKD stage 2 (HR = 1.36 [1.22–1.52] non-CKD; 1.34 [1.20–1.50] stage 2; 1.11 [0.79–1.55] stage 3). Before recalibration, FRAX globally overestimated fracture risk while QFracture and Garvan globally underestimated fracture risk. After recalibration, FRAX and QFracture were adequately calibrated for MOF in all CKD strata whereas Garvan tended to underestimate any fracture risk in CKD stage 3 (SIR = 1.31 [0.95–1.81]). In conclusion, the discrimination and calibration of FRAX and QFracture is similar in non-CKD and CKD. Garvan may have a lower discrimination in CKD stage 3 and underestimate fracture risk in these patients. © 2020 American Society for Bone and Mineral Research.     

慢性肾衰竭大鼠股骨cbfa1表达与骨密度关系的研究

目的探讨股骨核心结合因子-a1(cbfa1)对慢性肾衰竭大鼠股骨密度变化的影响。方法将12只大鼠随机分为空白对照组、慢性肾衰竭模型组。造模成功后测量各组大鼠股骨的整体骨密度(Whole-bone mineral density,W-BMD)、松质骨骨密度(Trabecular-bone mineral density,T-BMD)、皮质骨骨密度(Cortical-bone mineral density,C-BMD),留取血清测定钙、磷等生化参数,采用免疫组织化学和HE染色的方法分别检测大鼠股骨中Cbfa1蛋白的表达及松质骨和皮质骨的形态学改变。结果与空白对照组比较,慢性肾衰竭模型组W-BMD、C-BMD降低,T-BMD升高(P0.001);股骨松质骨Cbfa1表达增多,皮质骨Cbfa1表达减少(P0.001);相关分析显示W-BMD与皮质骨Cbfa1蛋白表达呈正相关(r=0.979,P0.001),与松质骨Cbfa1蛋白表达呈负相关(r=-0.974,P0.001),与血清钙浓度呈正相关(r=0.730,P0.001),与血清磷浓度呈负相关(r=-0.652,P0.001)。结论 Cbfa1是肾性骨病导致的骨密度改变的预测因素,可能是Cbfa1对骨形态的影响而导致骨密度的改变。     

Changing the current terminology in medicine--always a challenge.

Since 1943, when bone metabolic disorders associated with chronickidney disease (CKD) were described as ‘Renal Osteodystrophy’[1], the knowledge and scope of this disorder have experiencedrelevant changes and progress. The growth and the almost worldwidespread of renal replacement therapies (RRT) have largely contributedto the expansion and current daily use of this term among themedical community. As a result of changes in strategy, new activetreatments and longer survival in     

Clinical evaluation of two novel biointact PTH(1–84) assays in hemodialysis patients

Objectives

In chronic kidney disease–mineral and bone disorder (CKD-MBD), most treatment decisions are guided by parathyroid hormone (PTH) levels. Here, we aimed at assessing the technical and clinical performance of two novel automated biointact PTH(1–84) assays, from Roche Diagnostics (Ro) and DiaSorin (DS), in hemodialysis patients.

Design and methods

We recorded demographics, dialysis treatment characteristics, pharmacotherapy for CKD-MBD and laboratory work-up. Statistical methods included Passing–Bablok, and multiple linear regression.

Results

121 patients, dialyzing on average for 3.5 years (range: 0.1–22.5), with serum phosphate 1.9 ± 0.6 mmol/L (mean ± SD), participated in the study. Median serum concentration for intact PTH was 223 ng/L (range: 5–2844), and for biointact PTH(1–84) was 136 ng/L (Ro; range: 1–1644), respectively 138 ng/L (DS; range: 4-1580). Both biointact assays were significantly correlated (r = 0.98; Ro = 0.87 × DS + 19.60). Bland–Altmann plots revealed an average bias ± 2 SD of 10 ± 27 ng/L below 200 ng/L, and − 32 ± 157 ng/L above 200 ng/L (Ro minus DS). The variably adjusted association between PTH and serum phosphate was very similar, regardless of the PTH assay, but this was not the case for PTH-derived measures (ratios biointact/intact; differences intact minus biointact). (Log)PTH concentrations as well as serum phosphate were significantly associated with serum creatinine, but only in patients with > 0 mL urine per day.

Conclusions

Results from Roche and DiaSorin biointact PTH(1–84) assays were well correlated, but showed increased deviations at higher concentrations. Biointact PTH(1–84) levels are roughly two third of intact PTH. The association between PTH and serum creatinine may depend on residual renal clearance of PTH and/or serum phosphate.     

Routine Laboratory Testing Every 4 Versus Every 6 Weeks for Patients on Maintenance Hemodialysis: A Quality Improvement Project

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中心夜间透析和传统透析患者循环成纤维细胞生长因子23水平差异及影响因素

目的 比较中心夜间血液透析(INHD)和传统血液透析(CHD)患者循环成纤维细胞生长因子23(FGF23)水平差异并探讨影响患者FGF23水平的因素.方法 收集第二军医大学长征医院44例INHD及64例CHD患者空腹静脉血,测定患者钙、磷、全段甲状旁腺素(iPTH)、尿素清除指数(Kt/V)、25-羟维生素D、铁蛋白、血红蛋白、血脂、FGF23等指标并比较两组各指标的差异,采用多重线性回归分析探究FGF23的影响因素,Pearson相关性分析探究FGF23与血钙、血磷、钙磷乘积、iPTH、25-羟维生素D、Kt/V的相关性.结果 INHD患者血磷较CHD患者低(P＜0.05),INHD透析充分性明显高于CHD,INHD患者循环FGF23水平低于CHD患者(P＜0.05).FGF23与钙、磷、钙磷乘积相关(P＜0.01),与iPTH及Kt/V不相关.结论 INHD比CHD更能有效改善慢性肾脏病-矿物质和骨异常(CKD-MBD)参数.钙磷乘积是血液透析患者FGF23水平的独立影响因素,INHD通过减少钙磷乘积降低血清FGF23水平可能是其改善患者临床预后的机制之一.     

Osteoporosis,densidad mineral ósea y complejo CKD-MBD (I): consideraciones diagnósticas

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.