Associations of FGF-23 and sKlotho with Cardiovascular Outcomes among Patients with CKD Stages 2–4

Background and objectives

CKD–mineral and bone disorders (CKD-MBD) measures contribute to cardiovascular morbidity in patients with CKD. Among these, fibroblast growth factor (FGF)-23 and its coreceptor Klotho may exert direct effects on vascular and myocardial tissues. Klotho exists in a membrane-bound and a soluble form (sKlotho). Recent experimental evidence suggests sKlotho has vasculoprotective functions.

Design, settings, participants, & measurements

Traditional and novel CKD-MBD variables were measured among 444 patients with CKD stages 2–4 recruited between September 2008 and November 2012 into the ongoing CARE FOR HOMe study. Across tertiles of baseline sKlotho and FGF-23, the incidence of two distinct combined end points was analyzed: (1) the first occurrence of an atherosclerotic event or death from any cause and (2) the time until hospital admission for decompensated heart failure or death from any cause.

Results

Patients were followed for 2.6 (interquartile range, 1.4–3.6) years. sKlotho tertiles predicted neither atherosclerotic events/death (fully adjusted Cox regression analysis: hazard ratio [HR] for third versus first sKlotho tertile, 0.75 [95% confidence interval (95% CI), 0.43–1.30]; P=0.30) nor the occurrence of decompensated heart failure/death (HR for third versus first sKlotho tertile, 0.81 [95% CI, 0.39–1.66]; P=0.56). In contrast, patients in the highest FGF-23 tertile had higher risk for both end points in univariate analysis. Adjustment for kidney function attenuated the association between FGF-23 and atherosclerotic events/death (HR for third versus first FGF-23 tertile, 1.23 [95% CI, 0.58–2.61]; P=0.59), whereas the association between FGF-23 and decompensated heart failure/death remained significant after adjustment for confounders (HR for third versus first FGF-23 tertile, 4.51 [95% CI, 1.33–15.21]; P=0.02).

Conclusions

In this prospective observational study of limited sample size, sKlotho was not significantly related to cardiovascular outcomes. FGF-23 was significantly associated with future decompensated heart failure but not incident atherosclerotic events.     

Glycated Hemoglobin Level and Mortality in a Nondiabetic Population with CKD

Background and objectives

Glycated hemoglobin (HbA_1c) is used to diagnose diabetes mellitus (DM) and guide its management. The association between higher HbA_1c and progression to ESRD and mortality has been demonstrated in populations with DM. This study examined the association between HbA_1c and these end points in a population with CKD and without DM.

Design, setting, participants, & measurements

In the hospital-based NephroTest cohort study, measured GFR (mGFR) was taken by ⁵¹Cr-EDTA renal clearance and HbA_1c in 1165 adults with nondialysis CKD stages 1–5 and without DM between January 2000 and December 2010. The median follow-up was 3.48 years (interquartile range, 1.94–5.82) for the competing events of ESRD and pre-ESRD mortality. Time-fixed and time-dependent Cox models were used to estimate hazard ratios (HRs) for ESRD and mortality according to HbA_1c, treated continuously or in tertiles.

Results

At inclusion, the mean mGFR was 42.2±19.9 ml/min per 1.73 m², and the mean HbA_1c value was 5.5%±0.5%. During follow-up, 109 patients died, and 162 patients reached ESRD. Pre-ESRD mortality was significantly associated with HbA_1c treated continuously: for every 1% higher HbA_1c, the crude HR was 2.16 (95% confidence interval [95% CI], 1.27 to 3.68), and it was 1.85 (95% CI, 1.05 to 3.24) after adjustment for mGFR and other risk factors of death. After excluding incident diabetes over time, the updated mean of HbA_1c remained significantly associated with higher mortality risk: adjusted HR for the highest (5.7%–6.4%) versus the lowest tertile (<5.3%) was 2.62 (95% CI, 1.16 to 5.91). There was no association with ESRD risk after adjustment for risk factors of CKD progression.

Conclusions

In a CKD cohort, HbA_1c values in the prediabetes range are associated with mortality. Such values should be therefore included among the risk factors for negative outcomes in CKD populations.     

Risk of ESRD and Death in Patients with CKD Not Referred to a Nephrologist: A 7-Year Prospective Study

Background and objectives

Rising prevalence of CKD requires active involvement of general practitioners to limit ESRD and mortality risk. However, the outcomes of patients with CKD exclusively managed by general practitioners are ill defined.

Design, setting, participants, & measurements

We prospectively evaluated 30,326 adult patients with nondialysis CKD stages 1–5 who had never received consultation in tertiary nephrology care recruited from 700 general practitioner offices in Italy during 2002 and 2003. CKD stages were classified as stages 1 and 2 (GFR≥60 ml/min per 1.73 m² and either albuminuria or an International Classification of Diseases, Ninth Revision, Clinical Modification code for kidney disease), stage 3a (GFR=59–45), stage 3b (GFR=44–30), stage 4 (GFR=29–15), and stage 5 (GFR<15). Primary outcome was the risk of ESRD (dialysis or transplantation) or all-cause death.

Results

Overall 64% of patients were in stage 3a, and 4.5% of patients were in stages 3b–5. Patients with stages 1 and 2 were younger, were predominantly men, more frequently had diabetes, and had lower prevalence of previous cardiovascular disease than patients with stages 3a–5. Hypertension was frequent in all CKD stages (80%–94%), whereas there was a lower prevalence of dyslipidemia, albuminuria, and obesity associated with more advanced CKD. During the follow-up (median=7.2 years; interquartile range=4.7–7.7), 6592 patients died and 295 started ESRD. Compared with stages 1 and 2 (reference), mortality risk (hazard ratio, 95% confidence interval) was higher in stages 3b–5 (1.66, 1.49–1.86, 2.75, 2.41–3.13 and 2.54, 2.01–3.22, respectively) but not stage 3a (1.11, 0.99–1.23). Similarly, ESRD risk (hazard ratio, 95% confidence interval) was not higher at stage 3a (1.44, 0.79–2.64) but was greater in stages 3b–5 (11.0, 6.3–19.5, 91.2, 53.2–156.2 and, 122.8, 67.9–222.0, respectively). Among modifiable risk factors, anemia and albuminuria significantly predicted either outcome, whereas hypertension only predicted mortality.

Conclusions

In patients with CKD not referred to nephrology, risks of ESRD and mortality were higher in those with CKD stages 3b–5.     

Nephrolithiasis as a Risk Factor for CKD: The Atherosclerosis Risk in Communities Study

Background and objectives

Previous studies demonstrated a higher risk of CKD in persons with a history of kidney stones, but these studies examined mostly white populations and did not evaluate important potential interactions such as race and plasma uric acid.

Design, setting, participants, & measurements

In 10,678 Atherosclerosis Risk in Communities (ARIC) study participants free of CKD at baseline (ARIC visit 4 in 1996–1998), we assessed the association between a history of nephrolithiasis (a time-varying variable, defined by a combination of self-report and diagnostic codes) and incident CKD (defined by diagnostic codes from linkage to hospitalizations and US Centers for Medicare and Medicaid Services’ records).

Results

At baseline, 856 participants had a history of nephrolithiasis; 322 developed nephrolithiasis during follow-up. Over a mean follow-up of 12 years, there were 1037 incident CKD events. Nephrolithiasis history was associated with a 29% (hazard ratio [HR], 1.29; 95% confidence interval [95% CI], 1.07 to 1.54) higher risk of CKD in demographic-adjusted analyses, but the association was no longer statistically significant after multivariable adjustment (HR, 1.09; 95% CI, 0.90 to 1.32). The multivariable-adjusted association was stronger among participants with plasma uric acid levels ≤6 mg/dl (HR, 1.34; 95% CI, 1.05 to 1.72) compared with those with levels >6 mg/dl (HR, 0.94; 95% CI, 0.70 to 1.28; P_interaction=0.05). There was no interaction of stone disease and race with incident CKD.

Conclusions

In this community-based cohort, nephrolithiasis was not an independent risk factor for incident CKD overall. However, risk of CKD was unexpectedly elevated in participants with stone disease and lower plasma uric acid levels.     

Relation of Serum Lipids and Lipoproteins with Progression of CKD: The CRIC Study

Background and objectives

Hyperlipidemia is common in patients with CKD. The objective of this study was to evaluate whether measures of plasma lipids and lipoproteins predict progression of kidney disease in patients with CKD.

Design, setting, participants, & measurements

Prospective cohort study in adults (n=3939) with CKD aged 21–74 years recruited between 2003 and 2008 and followed for a median of 4.1 years. At baseline, total cholesterol, triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), apoA-I , apoB, and lipoprotein(a) [Lp(a)] were measured. The outcomes were composite end point of ESRD or 50% decline in eGFR from baseline (rate of change of GFR).

Results

Mean age of the study population was 58.2 years, and the mean GFR was 44.9 ml/min per 1.73 m²; 48% of patients had diabetes. None of the lipid or lipoprotein measures was independently associated with risk of the composite end point or rate of change in GFR. However, there were significant (P=0.01) interactions by level of proteinuria. In participants with proteinuria<0.2 g/d, 1-SD higher LDL-C was associated with a 26% lower risk of the renal end point (hazard ratio [HR], 0.74; 95% confidence interval [95% CI], 0.59 to 0.92; P=0.01), and 1-SD higher total cholesterol was associated with a 23% lower risk of the renal end point (HR, 0.77; 95% CI, 0.62 to 0.96; P=0.02). In participants with proteinuria>0.2 g/d, neither LDL-C (HR, 0.98; 95% CI, 0.98 to 1.05) nor total cholesterol levels were associated with renal outcomes. Treatment with statins was reported in 55% of patients and was differential across lipid categories.

Conclusions

In this large cohort of patients with CKD, total cholesterol, triglycerides, VLDL-C, LDL-C, HDL-C, apoA-I, apoB, and Lp(a) were not independently associated with progression of kidney disease. There was an inverse relationship between LDL-C and total cholesterol levels and kidney disease outcomes in patients with low levels of proteinuria.     

Light-Intensity Physical Activities and Mortality in the United States General Population and CKD Subpopulation

Background and objectives

Sedentary behavior is associated with increased mortality in the general population. Whether replacing sedentary behavior with low- or light-intensity activities confers a survival benefit in the general or CKD populations is unknown.

Design, setting, participants, & measurements

This observational analysis of the 2003–2004 National Health and Nutrition Examination Survey examined the associations of low- and light-intensity activities with mortality. On the basis of the number of counts/min recorded by an accelerometer, durations of sedentary (<100/min), low (100–499/min), light (500–2019/min), and moderate/vigorous (≥2020/min) activity were defined and normalized to 60 minutes. The mortality associations of 2 min/hr less sedentary duration in conjunction with 2 min/hr more (tradeoff) spent in one of the low, light, or moderate/vigorous activity durations while controlling for the other two activity durations were examined in multivariable Cox regression models in the entire cohort and in the CKD subgroup.

Results

Of the 3626 participants included, 383 had CKD. The mean sedentary duration was 34.4±7.9 min/hr in the entire cohort and 40.8±6.8 in the CKD subgroup. Tradeoff of sedentary duration with low activity duration was not associated with mortality in the entire cohort or the CKD subgroup. Tradeoff of sedentary duration with light activity duration was associated with a lower hazard of death in the entire cohort (hazard ratio, 0.67; 95% confidence interval, 0.48 to 0.93) and CKD subgroup (hazard ratio, 0.59; 95% confidence interval, 0.35 to 0.98). Tradeoff of sedentary duration with moderate/vigorous activity duration had a nonsignificant lower hazard in the entire cohort and CKD subgroup.

Conclusions

Patients with CKD are sedentary nearly two thirds of the time. Interventions that replace sedentary duration with an increase in light activity duration might confer a survival benefit.     

Examination of Potential Modifiers of the Association of APOL1 Alleles with CKD Progression

Background and objectives

Common apolipoprotein L1 (APOL1) variants are associated with increased risk of progressive CKD; however, not all individuals with high–risk APOL1 variants experience CKD progression. Identification of factors contributing to heterogeneity has important scientific and clinical implications.

Design, setting, participants, & measurements

Using multivariable Cox models, we analyzed data from 693 participants in the African American Study of Kidney Disease and Hypertension to identify factors that modify the association between APOL1 genotypes and CKD progression (doubling of serum creatinine or incident ESRD).

Results

Participant mean age was 54 years old, median GFR was 49 ml/min per 1.73 m², and 23% had the APOL1 high–risk genotype (two copies of the high-risk allele). Over a mean follow-up of 7.8 years, 288 (42%) participants experienced CKD progression. As previously reported, the high-risk genotype was associated with higher risk of CKD progression compared with the low-risk genotype (hazard ratio [HR], 1.88; 95% confidence interval [95% CI], 1.46 to 2.41). Although we found some suggestion that obesity (HR, 1.48; 95% CI, 1.05 to 2.08 and HR, 2.44; 95% CI, 1.66 to 3.57 for body mass index ≥30 versus <30 kg/m²; P interaction =0.04) and increased urinary excretion of urea nitrogen (HR, 1.43; 95% CI, 0.98 to 2.09 versus HR, 2.33; 95% CI, 1.65 to 3.30 for urine urea nitrogen ≥8 versus <8 g/d; P interaction =0.04) were associated with lower APOL1–associated risk for CKD progression, these findings were not robust in sensitivity analyses with alternative cut points. No other sociodemographic (e.g., education and income), clinical (e.g., systolic BP and smoking), or laboratory (e.g., net endogenous acid production, urinary sodium and potassium excretions, 25-hydroxy vitamin D, intact parathyroid hormone, or fibroblast growth factor 23) variables modified the association between APOL1 and CKD progression (P interaction >0.05 for each).

Conclusions

Sociodemographic factors and common risk factors for CKD progression do not seem to alter APOL1–related CKD progression. Additional investigation is needed to identify nontraditional factors that may affect the association between APOL1 and progressive CKD.     

Urinary Creatinine Excretion,Bioelectrical Impedance Analysis,and Clinical Outcomes in Patients with CKD: The CRIC Study

Background and objectives

Previous studies in chronic disease states have demonstrated an association between lower urinary creatinine excretion (UCr) and increased mortality, a finding presumed to reflect the effect of low muscle mass on clinical outcomes. Little is known about the relationship between UCr and other measures of body composition in terms of the ability to predict outcomes of interest.

Design, setting, participants, & measurements

Using data from the Chronic Renal Insufficiency Cohort (CRIC), the relationship between UCr, fat free mass (FFM) as estimated by bioelectrical impedance analysis, and (in a subpopulation) whole-body dual-energy x-ray absorptiometry assessment of appendicular lean mass were characterized. The associations of UCr and FFM with mortality and ESRD were compared using Cox proportional hazards models.

Results

A total of 3604 CRIC participants (91% of the full CRIC cohort) with both a baseline UCr and FFM measurement were included; of these, 232 had contemporaneous dual-energy x-ray absorptiometry measurements. Participants were recruited between July 2003 and March 2007. UCr and FFM were modestly correlated (rho=0.50; P<0.001), while FFM and appendicular lean mass were highly correlated (rho=0.91; P<0.001). Higher urinary urea nitrogen, black race, younger age, and lower serum cystatin C level were all significantly associated with higher UCr. Over a median (interquartile range) of 4.2 (3.1–5.0) years of follow-up, 336 (9.3%) participants died and 510 (14.2%) reached ESRD. Lower UCr was associated with death and ESRD even after adjustment for FFM (adjusted hazard ratio for death per 1 SD higher level of UCr, 0.63 [95% confidence interval, 0.56 to 0.72]; adjusted hazard ratio for ESRD per 1 SD higher level of UCr, 0.70 [95% confidence interval, 0.63 to 0.75]).

Conclusions

Among a cohort of individuals with CKD, lower UCr is associated with death and ESRD independent of FFM as assessed by bioelectrical impedance analysis.     

Prognosis of CKD Patients Receiving Outpatient Nephrology Care in Italy

Summary

Background and objectives

Prognosis in nondialysis chronic kidney disease (CKD) patients under regular nephrology care is rarely investigated.

Design, setting, participants, & measurements

We prospectively followed from 2003 to death or June 2010 a cohort of 1248 patients with CKD stages 3 to 5 and previous nephrology care ≥1 year in 25 Italian outpatient nephrology clinics. Cumulative incidence of ESRD or death before ESRD were estimated using the competing-risk approach.

Results

Estimated rates (per 100 patient-years) of ESRD and death 8.3 (95% confidence interval [CI], 7.4 to 9.2) and 5.9 (95% CI 5.2 to 6.6), respectively. Risk of ESRD and death increased progressively from stages 3 to 5. ESRD was more frequent than death in stage 4 and 5 CKD, whereas the opposite was true in stage 3 CKD. Younger age, lower body mass index, proteinuria, and high phosphate predicted ESRD, whereas older age, diabetes, previous cardiovascular disease, ESRD, proteinuria, high uric acid, and anemia predicted death (P < 0.05 for all). Among modifiable risk factors, proteinuria accounted for the greatest contribution to the model fit for either outcome.

Conclusions

In patients receiving continuity of care in Italian nephrology clinics, ESRD was a more frequent outcome than death in stage 4 and 5 CKD, but the opposite was true in stage 3. Outcomes were predicted by modifiable risk factors specific to CKD. Proteinuria used in conjunction with estimated GFR refined risk stratification. These findings provide information, specific to CKD patients under regular outpatient nephrology care, for risk stratification that complement recent observations in the general population.     

Outcomes After Post-Traumatic AKI Requiring RRT in United States Military Service Members

Background and objectives

Mortality and CKD risk have not been described in military casualties with post-traumatic AKI requiring RRT suffered in the Iraq and Afghanistan wars.

Design, setting, participants, & measurements

This is a retrospective case series of post-traumatic AKI requiring RRT in 51 military health care beneficiaries (October 7, 2001–December 1, 2013), evacuated to the National Capital Region, documenting in-hospital mortality and subsequent CKD. Participants were identified using electronic medical and procedure records.

Results

Age at injury was 26±6 years; of the participants, 50 were men, 16% were black, 67% were white, and 88% of injuries were caused by blast or projectiles. Presumed AKI cause was acute tubular necrosis in 98%, with rhabdomyolysis in 72%. Sixty-day all-cause mortality was 22% (95% confidence interval [95% CI], 12% to 35%), significantly less than the 50% predicted historical mortality (P<0.001). The VA/NIH Acute Renal Failure Trial Network AKI integer score predicted 60-day mortality risk was 33% (range, 6%–96%) (n=49). Of these, nine died (mortality, 18%; 95% CI, 10% to 32%), with predicted risks significantly miscalibrated (P<0.001). The area under the receiver operator characteristic curve for the AKI integer score was 0.72 (95% CI, 0.56 to 0.88), not significantly different than the AKI integer score model cohort (P=0.27). Of the 40 survivors, one had ESRD caused by cortical necrosis. Of the remaining 39, median time to last follow-up serum creatinine was 1158 days (range, 99–3316 days), serum creatinine was 0.85±0.24 mg/dl, and eGFR was 118±23 ml/min per 1.73 m². No eGFR was <60 ml/min per 1.73 m², but it may be overestimated because of large/medium amputations in 54%. Twenty-five percent (n=36) had proteinuria; one was diagnosed with CKD stage 2.

Conclusions

Despite severe injuries, participants had better in-hospital survival than predicted historically and by AKI integer score. No patient who recovered renal function had an eGFR<60 ml/min per 1.73 m² at last follow-up, but 23% had proteinuria, suggesting CKD burden.     

Temporal Trajectory of B-Type Natriuretic Peptide in Patients with CKD Stages 3 and 4, Dialysis,and Kidney Transplant

Background and objectives

B-type natriuretic peptide (BNP) concentration predicts outcome in patients undergoing dialysis. Because survival and cardiovascular risk change across the CKD continuum, serial changes in BNP were compared in patients at different CKD stages and after kidney transplantation.

Design, setting, participants, & measurements

Patients with CKD stages 3 and 4 (CKD 3–4), dialysis patients, and kidney transplant recipients (KTRs) from one center had two measurements of BNP taken a median of 161 days apart in 2003–2004 and were followed until July 2012. Both BNP-32 (Triage BNP; Biosite Diagnostics) and NT-BNP-76 (proBNP; Roche Diagnostics) were assayed. The interaction between change in log-transformed BNP concentration over time and patient group was tested by fitting regression models on panel data with random effects. Survival after the second measurement was compared by tertile of change in BNP.

Results

Patients with CKD 3–4 (n=48), dialysis patients (n=102), and KTRs (n=73) were followed for a median of 5.7, 4.8, and 5.9 years, respectively. The interaction between patient group and BNP measurements over time was significant for NT-BNP-76 (P<0.001) and BNP-32 (P<0.01). Median NT-BNP-76 increased in dialysis patients and those with CKD 3–4 from 3850 pg/ml (interquartile range [IQR], 1776–12,323 pg/ml) to 18,830 pg/ml (IQR, 6114–61,009 pg/ml; P<0.001) and from 698 pg/ml (IQR, 283–2922 pg/ml) to 2529 pg/ml (IQR, 347–9277 pg/ml; P=0.002), respectively. Change was not significant for KTRs or comparisons made with BNP-32. Survival rate was significantly lower for patients with the highest tertile of change in NT-BNP-76 among patients with CKD 3–4 (P=0.02), but not in the dialysis or KTR groups. In 11 patients who received a kidney transplant during the study, median NT-BNP-76 decreased from 9607 pg/ml (IQR, 2292–31,282 pg/ml) to 457 pg/ml (IQR, 203–863 pg/ml) after transplant (P<0.01).

Conclusions

The temporal trajectory of BNP differs between dialysis patients and those with CKD 3–4 and KTRs. This has important implications for the development of BNP-guided management strategies in CKD.     

Risk Prediction for Early CKD in Type 2 Diabetes

Background and objectives

Quantitative data for prediction of incidence and progression of early CKD are scarce in individuals with type 2 diabetes. Therefore, two risk prediction models were developed for incidence and progression of CKD after 5.5 years and the relative effect of predictors were ascertained.

Design, setting, participants, & measurements

Baseline and prospective follow-up data of two randomized clinical trials, ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET) and Outcome Reduction with Initial Glargine Intervention (ORIGIN), were used as development and independent validation cohorts, respectively. Individuals aged ≥55 years with type 2 diabetes and normo- or microalbuminuria at baseline were included. Incidence or progression of CKD after 5.5 years was defined as new micro- or macroalbuminuria, doubling of creatinine, or ESRD. The competing risk of death was considered as an additional outcome state in the multinomial logistic models.

Results

Of the 6766 ONTARGET participants with diabetes, 1079 (15.9%) experienced incidence or progression of CKD, and 1032 (15.3%) died. The well calibrated, parsimonious laboratory prediction model incorporating only baseline albuminuria, eGFR, sex, and age exhibited an externally validated c-statistic of 0.68 and an R² value of 10.6%. Albuminuria, modeled to depict the difference between baseline urinary albumin/creatinine ratio and the threshold for micro- or macroalbuminuria, was mostly responsible for the predictive performance. Inclusion of clinical predictors, such as glucose control, diabetes duration, number of prescribed antihypertensive drugs, previous vascular events, or vascular comorbidities, increased the externally validated c-statistic and R² value only to 0.69 and 12.1%, respectively. Explained variation was largely driven by renal and not clinical predictors.

Conclusions

Albuminuria and eGFR were the most important factors to predict onset and progression of early CKD in individuals with type 2 diabetes. However, their predictive ability is modest. Inclusion of demographic, clinical, and other laboratory predictors barely improved predictive performance.     

Plasma Vitamin D Level and Change in Albuminuria and eGFR According to Sodium Intake

Background and objectives

Low circulating 25-hydroxyvitamin D [25(OH)D] and high sodium intake are both associated with progressive albuminuria and renal function loss in CKD. Both vitamin D and sodium intake interact with the renin-angiotensin-aldosterone system. We investigated whether plasma 25(OH)D or 1,25-dihydroxyvitamin D [1,25(OH)₂D] is associated with developing increased albuminuria or reduced renal function and whether these associations depend on sodium intake.

Design, setting, participants, & measurements

Baseline plasma 25(OH)D and 1,25(OH)₂D were measured by liquid chromatography tandem mass spectrometry, and sodium intake was assessed by 24-hour urine collections in the general population–based Prevention of Renal and Vascular End-Stage Disease cohort (n=5051). Two primary outcomes were development of urinary albumin excretion >30 mg/24 h and eGFR (creatinine/cystatin C–based CKD Epidemiology Collaboration) <60 ml/min per 1.73 m². Participants with CKD at baseline were excluded. In Cox regression analyses, we assessed associations of vitamin D with developing increased albuminuria or reduced eGFR and potential interaction with sodium intake.

Results

During a median follow-up of 10.4 (6.2–11.4) years, 641 (13%) participants developed increased albuminuria, and 268 (5%) participants developed reduced eGFR. Plasma 25(OH)D was inversely associated with increased albuminuria (fully adjusted hazard ratio [HR] per SD higher, 0.86; 95% confidence interval [95% CI], 0.78 to 0.95; P=0.003) but not reduced eGFR (HR, 0.99; 95% CI, 0.87 to 1.12; P=0.85). There was interaction between 25(OH)D and sodium intake for risk of developing increased albuminuria (P interaction =0.03). In participants with high sodium intake, risk of developing increased albuminuria was inversely associated with 25(OH)D (lowest versus highest quartile: adjusted HR, 1.81; 95% CI, 1.20 to 2.73, P<0.01), whereas this association was nonsignificant in participants with low sodium intake (HR, 1.29; 95% CI, 0.94 to 1.77; P=0.12). Plasma 1,25(OH)₂D was not significantly associated with increased albuminuria or reduced eGFR.

Conclusions

Low plasma 25(OH)D is associated with higher risk of developing increased albuminuria, particularly in individuals with high sodium intake, but not of developing reduced eGFR. Plasma 1,25(OH)2D is not associated with risk of developing increased albuminuria or reduced eGFR.     

Retinopathy and Progression of CKD: The CRIC Study

Background and objectives

Retinal abnormalities may be associated with changes in the renal vasculature. This study assessed the association between retinopathy and progression of kidney disease in participants of the Chronic Renal Insufficiency Cohort (CRIC) study.

Design, setting, participants, & measurements

This was a prospective study in which patients with CKD enrolled in CRIC had nonmydriatic fundus photographs of both eyes. All CRIC participants in six clinical sites in which fundus cameras were deployed were offered participation. Photographs were reviewed at a reading center. The presence and severity of retinopathy and vessel calibers were assessed using standard protocols by graders masked to clinical information. The associations of retinal features with changes in eGFR and the need for RRT (ESRD) were assessed.

Results

Retinal images and renal progression outcomes were obtained from 1852 of the 2605 participants (71.1%) approached. During follow-up (median 2.3 years), 152 participants (8.2%) developed ESRD. Presence and severity of retinopathy at baseline were strongly associated with the risk of subsequent progression to ESRD and reductions in eGFR in unadjusted analyses. For example, participants with retinopathy were 4.4 times (95% confidence interval [95% CI], 3.12 to 6.31) more likely to develop ESRD than those without retinopathy (P<0.001). However, this association was not statistically significant after adjustment for initial eGFR and 24-hour proteinuria. Venular and arteriolar diameter calibers were not associated with ESRD or eGFR decline. The results showed a nonlinear relationship between mean ratio of arteriole/vein calibers and the risk of progression to ESRD; participants within the fourth arteriole/vein ratio quartile were 3.11 times (95% CI, 1.51 to 6.40) more likely to develop ESRD than those in the first quartile (P<0.001).

Conclusions

The presence and severity of retinopathy were not associated with ESRD and decline in eGFR after taking into account established risk factors.     

Association of Walking with Survival and RRT Among Patients with CKD Stages 3–5

Background and objectives

Patients with CKD can benefit from an increase in physical activity. Walking is one of the most common exercises in patients with CKD; however, the association of walking with outcomes in patients with CKD is not clear. This study investigated the association of walking with overall mortality and RRT in patients with CKD stages 3–5.

Design, setting, participants, & measurements

All patients with CKD stages 3–5 in the CKD program of China Medical University Hospital from June 2003 to May 2013 were enrolled. The risks of overall mortality and RRT were analyzed using competing-risks regressions.

Results

A total of 6363 patients (average age, 70 years) during a median of 1.3 (range=0.6–2.5) years of follow-up were analyzed. There were 1341 (21.1%) patients who reported walking as their most common form of exercise. The incidence density rate of overall mortality was 2.7 per 100 person-years for walking patients and 5.4 for nonwalking ones. The incidence density rate of RRT was 22 per 100 person-years for walking patients and 32.9 for nonwalking ones. Walking, independent of patients’ age, renal function, and comorbidity, was linked to lower overall mortality and lower RRT risk in the multivariate competing-risks regression. The adjusted subdistribution hazard ratio (SHR) of walking was 0.67 (95% confidence interval [95% CI], 0.53 to 0.84; P<0.001) for overall mortality and 0.79 (95% CI, 0.73 to 0.85; P<0.001) for the risk of RRT. The SHRs of overall mortality were 0.83, 0.72, 0.42, and 0.41 for patients walking 1–2, 3–4, 5–6, and ≥7 times per week, and the SHRs of RRT were 0.81, 0.73, 0.57, and 0.56, respectively.

Conclusions

Walking is the most popular form of exercise in patients with CKD and is associated with lower risks of overall mortality and RRT. The benefit of walking is independent of patients’ age, renal function, and comorbidity.     

Associations of Left Ventricular Hypertrophy and Geometry with Adverse Outcomes in Patients with CKD and Hypertension

Background and objectives

Left ventricular hypertrophy (LVH) and abnormal left ventricular (LV) geometry predict adverse outcomes in the general and hypertensive populations, but findings in CKD are still inconclusive.

Design, setting, participants, & measurements

We enrolled 445 patients with hypertension and CKD stages 2–5 in two academic nephrology clinics in 1999–2003 who underwent both echocardiography and ambulatory BP monitoring. LVH (LV mass >100 g/m² [women] and >131 g/m² [men]) and relative wall thickness (RWT) were used to define LV geometry: no LVH and RWT≤0.45 (normal), no LVH and RWT>0.45 (remodeling), LVH and RWT≤0.45 (eccentric), and LVH and RWT>0.45 (concentric). We evaluated the prognostic role of LVH and LV geometry on cardiovascular (CV; composite of fatal and nonfatal events) and renal outcomes (composite of ESRD and all-cause death).

Results

Age was 64.1±13.8 years old; 19% had diabetes, and 22% had CV disease. eGFR was 39.9±20.2 ml/min per 1.73 m². LVH was detected in 249 patients (56.0%); of these, 125 had concentric LVH, and 124 had eccentric pattern, whereas 71 patients had concentric remodeling. Age, women, anemia, and nocturnal hypertension were independently associated with both concentric and eccentric LVH, whereas diabetes and history of CV disease associated with eccentric LVH only, and CKD stages 4 and 5 associated with concentric LVH only. During follow-up (median, 5.9 years; range, 0.04–15.3), 188 renal deaths (112 ESRD) and 103 CV events (61 fatal) occurred. Using multivariable Cox analysis, concentric and eccentric LVH was associated with higher risk of CV outcomes (hazard ratio [HR], 2.59; 95% confidence interval [95% CI], 1.39 to 4.84 and HR, 2.79; 95% CI, 1.47 to 5.26, respectively). Similarly, greater risk of renal end point was detected in concentric (HR, 2.33; 95% CI, 1.44 to 3.80) and eccentric (HR, 2.30; 95% CI, 1.42 to 3.74) LVH. Sensitivity analysis using LVH and RWT separately showed that LVH but not RWT was associated with higher cardiorenal risk.

Conclusions

In patients with CKD, LVH is a strong predictor of the risk of poor CV and renal outcomes independent from LV geometry.     

Long-Term Risk of Cancer in Survivors of Pediatric ESRD

Background and objectives

ESRD is associated with an increased risk of malignancies. We analyzed the incidence of cancer in patients with pediatric ESRD after long–term follow-up.

Design, setting, participants, & measurements

All Dutch patients born before 1979 who were transplanted at age <15 years old in 1972–1992 were followed until 2010. We explored type and incidence of malignancies in patients compared with the general population using the National Cancer Registry.

Results

After a median of 25.3 years (1.3–37.8) of transplantation and at a median age of 33.5 years old (11.0–49.0), 105 primary malignancies had occurred in 54 of 249 patients. Among them, cutaneous squamous cell carcinoma was most frequent. Patients ages 25–30 years old had developed 16.5 times (95% confidence interval, 7.9 to 34.6) as many de novo tumors and 991 times (95% confidence interval, 313 to 3137) as many de novo cutaneous squamous cell carcinomas as their general population counterparts; in survivors ages 45–50 years old, these numbers were 81.5 (95% confidence interval, 50.7 to 131.1) and 2610 (95% confidence interval, 1596 to 4267), respectively. Cumulative incidence competing risk analysis showed that, after 30 years of transplantation, 41% of the survivors had developed cancer; 31% had developed a second de novo cancer <1 year after initial cancer diagnosis.

Conclusions

Cancer is highly prevalent among patients with pediatric ESRD after 25.3 years of transplantation, with a high rate of recurrence.     

Association of Serum Ig Free Light Chains with Mortality and ESRD among Patients with Nondialysis-Dependent CKD

Background and objectives

High levels of serum polyclonal combined Ig free light chains are associated with inflammation and decreased excretory kidney function, and they are an independent risk factor for mortality. Whether combined Ig free light chain predicted mortality and progression to ESRD in a stages 3–5 CKD cohort was assessed.

Design, setting, participants, & measurements

This was a prospective cohort study of 872 patients with stages 3–5 CKD (nondialysis) recruited into the Chronic Renal Insufficiency Standards Implementation Study. Patients were recruited to the Chronic Renal Insufficiency Standards Implementation Study in an unselected manner from secondary care nephrology clinics between 2004 and 2010. Combined Ig free light chain was measured at recruitment and analyzed by quartiles. The cohort was followed up for a median of 41.4 months (interquartile range =28.3–68.0 months). Cox regression analysis was undertaken to determine the variables associated with mortality and progression to ESRD.

Results

Combined Ig free light chain quartiles were <49.4, 49.4–68.8, 68.9–100.7, and >100.7 mg/L. An independent association with death and progression to ESRD was associated with the third and fourth combined Ig free light chain quartiles (quartile 3: death: hazard ratio, 1.49; 95% confidence interval, 1.02 to 2.18; P=0.04; ESRD: hazard ratio, 1.72; 95% confidence interval, 1.0 to 2.97; P=0.05; quartile 4: death: hazard ratio, 1.99; 95% confidence interval, 1.34 to 2.93; P<0.001; ESRD: hazard ratio, 3.73; 95% confidence interval, 2.1 to 6.3; P<0.001). The other independent risk factors were (1) preexisting cardiovascular disease, age >65 years old, and eGFR=15–30 ml/min per 1.73 m² for death and (2) age ≤65 years old, eGFR<30 ml/min per 1.73 m², urinary protein-to-creatinine ratio >30 mg/mmol, and serum phosphate level >4.65 mg/dl for progression to ESRD.

Conclusions

An elevated serum combined Ig free light chain level is an independent risk factor for mortality and progression to ESRD in patients with stages 3–5 CKD managed in secondary care.     

Decreased Conversion of 25-hydroxyvitamin D3 to 24,25-dihydroxyvitamin D3 Following Cholecalciferol Therapy in Patients with CKD

Background and objectives

Elevated concentrations of fibroblast growth factor 23 (FGF23) are postulated to promote 25-hydroxyvitamin D (25[OH]D) insufficiency in CKD by stimulating 24-hydroxylation of this metabolite, leading to its subsequent degradation; however, prospective human studies testing this relationship are lacking.

Design, setting, participants, & measurements

An open-label prospective study was conducted from October 2010 through July 2012 to compare the effect of 8 weeks of oral cholecalciferol therapy (50,000 IU twice weekly) on the production of 24,25(OH)₂D₃ in vitamin D–insufficient patients with CKD (n=15) and controls with normal kidney function (n=15). Vitamin D metabolites were comprehensively profiled at baseline and after treatment, along with FGF23 and other mineral metabolism parameters.

Results

Vitamin D₃ and 25(OH)D₃ concentrations increased equivalently in the CKD and control groups following cholecalciferol treatment (median D₃ change, 8.6 ng/ml [interquartile range, 3.9–25.6 ng/ml] for controls versus 12.6 ng/ml [6.9–41.2 ng/ml] for CKD [P=0.15]; 25(OH)D₃ change, 39.2 ng/ml [30.9–47.2 ng/ml] for controls versus 39.9 ng/ml [31.5–44.1 ng/ml] for CKD [P=0.58]). Likewise, the absolute increase in 1α,25(OH)₂D₃ was similar between CKD participants and controls (change, 111.2 pg/ml [64.3–141.6 pg/ml] for controls versus 101.1 pg/ml [74.2–123.1 pg/ml] for CKD; P=0.38). Baseline and post-treatment 24,25(OH)₂D₃ concentrations were lower in the CKD group; moreover, the absolute increase in 24,25(OH)₂D₃ after therapy was markedly smaller in patients with CKD (change, 2.8 ng/ml [2.3–3.5 ng/ml] for controls versus 1.2 ng/ml [0.6–1.9 ng/ml] for patients with CKD; P<0.001). Furthermore, higher baseline FGF23 concentrations were associated with smaller increments in 24,25(OH)₂D₃ for individuals with CKD; this association was negated after adjustment for eGFR by multivariate analysis.

Conclusions

Patients with CKD exhibit an altered ability to increase serum 24,25(OH)₂D₃ after cholecalciferol therapy, suggesting decreased 24-hydroxylase activity in CKD. The observed relationship between baseline FGF23 and increments in 24,25(OH)₂D₃ further refutes the idea that FGF23 directly contributes to 25(OH)D insufficiency in CKD through stimulation of 24-hydroxylase activity.     

Associations of Soluble CD14 and Endotoxin with Mortality,Cardiovascular Disease,and Progression of Kidney Disease among Patients with CKD

Background and objectives

CD14 plays a key role in the innate immunity as pattern-recognition receptor of endotoxin. Higher levels of soluble CD14 (sCD14) are associated with overall mortality in hemodialysis patients. The influence of kidney function on plasma sCD14 levels and its relationship with adverse outcomes in patients with CKD not yet on dialysis is unknown. This study examines the associations between plasma levels of sCD14 and endotoxin with adverse outcomes in patients with CKD.

Design, setting, participants, & measurements

We measured plasma levels of sCD14 and endotoxin in 495 Leuven Mild-to-Moderate CKD Study participants. Mild-to-moderate CKD was defined as presence of kidney damage or eGFR<60 ml/min per 1.73 m² for ≥3 months, with exclusion of patients on RRT. Study participants were enrolled between November 2005 and September 2006.

Results

Plasma sCD14 was negatively associated with eGFR (ρ=–0.34, P<0.001). During a median follow-up of 54 (interquartile range, 23–58) months, 53 patients died. Plasma sCD14 was predictive of mortality, even after adjustment for renal function, Framingham risk factors, markers of mineral bone metabolism, and nutritional and inflammatory parameters (hazard ratio [HR] per SD higher of 1.90; 95% confidence interval [95% CI],1.32 to 2.74; P<0.001). After adjustment for the same risk factors, plasma sCD14 was also a predictor of cardiovascular disease (HR, 1.30; 95% CI, 1.00 to 1.69; P=0.05). Although plasma sCD14 was associated with progression of CKD, defined as reaching ESRD or doubling of serum creatinine in models adjusted for CKD-specific risk factors (HR, 1.24; 95% CI, 1.01 to 1.52; P=0.04), significance was lost when adjusted for proteinuria (HR, 1.19; 95% CI, 0.96 to 1.48; P=0.11). There was neither correlation between plasma endotoxin and sCD14 (ρ=–0.06, P=0.20) nor was endotoxin independently associated with adverse outcome during follow-up.

Conclusions

Plasma sCD14 is elevated in patients with decreased kidney function and associated with mortality and cardiovascular disease in patients with CKD not yet on dialysis.