Twenty-Four-Hour Ambulatory Blood Pressure versus Clinic Blood Pressure Measurements and Risk of Adverse Outcomes in Children with CKD

BACKGROUND

and objectives Our objective was to determine whether clinic BPs (taken at either a single visit or two sequential visits) are inferior to ambulatory BPs in their ability to discriminate risk of adverse outcomes in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We included 513 participants of the CKD in Children Study who had clinic BPs and 24-hour ambulatory BP monitoring performed during similar timeframes. Predictors of interest were systolic BPs taken at a single visit or two repeated visits within a 1-year period compared with mean wake and sleep systolic ambulatory BPs. Outcomes were left ventricular hypertrophy and ESKD. We determined the ability for each BP parameter to provide risk discrimination using c statistics.

RESULTS

During mean follow-up of 3.5 years, 123 participants developed ESKD. In cross-sectional unadjusted analysis, every 0.1 increase in systolic BP index was associated with a 2.0 times higher odds of left ventricular hypertrophy (95% confidence interval, 1.5 to 2.8) by clinic BPs versus 1.8 times higher odds (95% confidence interval, 1.3 to 2.4) by ambulatory wake BP. The c statistic was highest for clinic BP (c=0.65; 95% confidence interval, 0.58 to 0.73) but similar to ambulatory wake BP (c=0.64; 95% confidence interval, 0.57 to 0.71) for the discrimination of left ventricular hypertrophy. In longitudinal unadjusted analysis, every 0.1 increase in systolic BP index was associated with a higher risk of ESKD using repeated clinic (hazard ratio, 1.5; 95% confidence interval, 1.3 to 1.8) versus ambulatory wake BP (hazard ratio, 1.6; 95% confidence interval, 1.3 to 2.0). Unadjusted c statistics were the same for wake (c=0.61; 95% confidence interval, 0.56 to 0.67) and clinic systolic BPs (c=0.61; 95% confidence interval, 0.55 to 0.66) for discriminating risk of ESKD.

CONCLUSIONS

Clinic BPs taken in a protocol-driven setting are not consistently inferior to ambulatory BP in the discrimination of BP-related adverse outcomes in children with CKD.

Brain Magnetic Resonance Imaging Findings in Children and Young Adults With CKD

BACKGROUND

The neuroanatomic basis for cognitive impairment in chronic kidney disease (CKD) is incompletely characterized. We performed advanced quantitative structural magnetic resonance imaging (MRI) to determine whether CKD affects brain structure and whether poorer neurocognitive performance in CKD is associated with structural brain differences.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

85 individuals with CKD stages 2 to 5 and 63 healthy controls, aged 8 to 25 years PREDICTORS: CKD versus control, estimated glomerular filtration rate (eGFR), and kidney transplant status were analyzed as predictors of MRI findings. MRI volumes in 19 prespecified regions of gray matter (GM), white matter (WM), and cerebrospinal fluid were analyzed as predictors of neurocognitive performance (median z scores) in 7 prespecified domains.

OUTCOMES

19 prespecified brain regions of interest (ROIs) in 7 prespecified domains. Neurocognitive performance in 7 prespecified domains.

MEASUREMENTS

ROI volumes were compared in CKD versus controls using unadjusted t tests and analysis of covariance (ANCOVA). Associations of ROI volumes with eGFR and kidney transplant status in participants with CKD were analyzed using ANCOVA and linear regression. Associations of neurocognitive performance and ROI volumes were analyzed by linear regression.

RESULTS

Participants with CKD had lower whole-brain, cortical, and left parietal GM volumes than controls in unadjusted analyses, but no differences were found in adjusted analysis. In participants with CKD, lower eGFR was associated with higher WM volume in whole-brain (P=0.05) and frontal (P=0.04) ROIs, but differences were not significant after multiple comparisons correction. Kidney transplant recipients had lower GM volumes in whole-brain (P=0.01; Q=0.06), frontal (P=0.02; Q=0.08), and left and right parietal (P=0.01; Q=0.06; and P=0.03; Q=0.1) ROIs and higher whole-brain WM volume (P=0.04; Q=0.1). Neurocognitive performance in the CKD group was not associated with ROI volumes.

LIMITATIONS

Unable to assess changes in brain structure and kidney function over time; analysis limited to prespecified ROIs and neurocognitive domains.

CONCLUSIONS

CKD in children and young adults may be associated with lower GM and higher WM volumes in some ROIs. Differences were relatively subtle in the CKD group as a whole, but were more prominent in recipients of a kidney transplant. However, neurocognitive performance was not explained by differences in brain ROI volumes, suggesting a functional rather than structural basis for neurocognitive impairment in CKD.

Use of the Kidney Failure Risk Equation to Determine the Risk of Progression to End-stage Renal Disease in Children With Chronic Kidney Disease

IMPORTANCE

The kidney failure risk equation (KFRE) has been shown to accurately estimate progression to kidney failure in adults with chronic kidney disease (CKD). Use of the KFRE in children with CKD, if accurate, would help to optimize planning for end-stage renal disease (ESRD) care.

OBJECTIVE

To determine whether the KFRE adequately discriminates the risk of ESRD in children with CKD.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study included 603 children with an estimated glomerular filtration rate of less than 60 mL/min/1.73 m2 in the Chronic Kidney Disease in Children study, a national multicenter observational study. Data were collected from January 1, 2005, through July 31, 2013, and analyzed from September 30, 2016, through September 8, 2017.

EXPOSURES

The primary predictive factors were the 4-variable (age, sex, bedside Schwartz estimated glomerular filtration rate, and ratio of albumin to creatinine levels) and 8-variable (4 variables plus serum calcium, phosphate, bicarbonate, and albumin levels) KFREs, which provide 1-, 2-, and 5-year estimates of the risk of progression to ESRD.

MAIN OUTCOMES AND MEASURES

Time to ESRD. The Cox proportional hazards model was used to examine the association between the KFRE score and time to ESRD. C statistics were used to discriminate ESRD risk by the KFRE, with a value of greater than 0.80 indicating strong discrimination.

RESULTS

Of the 603 children included in the study, 378 were boys (62.7%) and 225 were girls (37.3%); median age at study entry was 12 years (interquartile range, 8-15 years). Median estimated glomerular filtration rate was 44 mL/min/1.73 m2. Four hundred fifty-seven participants (75.8%) had a nonglomerular cause of CKD. Median observation time was 3.8 years (interquartile range, 1.7-6.2 years); 144 (23.9%) developed ESRD within 5 years of enrollment. The 4-variable KFRE scores discriminated risk of ESRD, with C statistics of 0.90, 0.86, and 0.81 for the 1-, 2-, and 5-year risk scores, respectively. Results were similar using the 8-variable equation.

CONCLUSIONS AND RELEVANCE

The KFRE is a simple tool that provides excellent discrimination of the risk of ESRD. Results suggest that the KFRE could be incorporated into the clinical care of children with CKD to aid in anticipatory guidance, timing of referral for transplant evaluation, and planning for dialysis access.

APOL1-associated glomerular disease among African-American children: a collaboration of the Chronic Kidney Disease in Children (CKiD) and Nephrotic Syndrome Study Network (NEPTUNE) cohorts

Background

Individuals of African ancestry harboring two variant alleles within apolipoprotein L1 ( APOL1 ) are classified with a high-risk (HR) genotype. Adults with an HR genotype have increased risk of focal segmental glomerulosclerosis and chronic kidney disease compared with those with a low-risk (LR) genotype (0 or 1 variants). The role of APOL1 risk genotypes in children with glomerular disease is less well known.

Methods

This study characterized 104 African-American children with a glomerular disease by APOL1 genotype in two cohorts: the Chronic Kidney Disease in Children (CKiD) and Nephrotic Syndrome Study Network (NEPTUNE).

Results

Among these subjects, 46% had an HR genotype with a similar age at cohort enrollment. For APOL1 HR children, the median age of disease onset was older (CKiD: 4.5 versus 11.5 years for LR versus HR; NEPTUNE: 11 versus 14 years for LR versus HR, respectively) and preterm birth was more common [CKiD: 27 versus 4%; NEPTUNE: 26 versus 12%; combined odds ratio 4.6 (95% confidence interval: 1.4, 15.5)]. Within studies, HR children had lower initial estimated glomerular filtration rate (eGFR) (CKiD: 53 versus 69 mL/min/1.73 m 2 ; NEPTUNE: 74 versus 94 mL/min/1.73 m 2 ). Longitudinal eGFR decline was faster among HR children versus LR (CKiD: -18 versus -8% per year; NEPTUNE: -13 versus -3% per year).

Conclusions

Children with an HR genotype in CKiD and NEPTUNE seem to have a more aggressive form of glomerular disease, in part due to a higher prevalence of focal segmental glomerulosclerosis. These consistent findings across independent cohorts suggest a common natural history for children with APOL1 -associated glomerular disease. Further study is needed to determine the generalizability of these findings.

FGF23 and Left Ventricular Hypertrophy in Children with CKD

BACKGROUND AND OBJECTIVES

High plasma concentration of fibroblast growth factor 23 (FGF23) is a risk factor for left ventricular hypertrophy (LVH) in adults with CKD, and induces myocardial hypertrophy in experimental CKD. We hypothesized that high FGF23 levels associate with a higher prevalence of LVH in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed echocardiograms and measured plasma C-terminal FGF23 concentrations in 587 children with mild-to-moderate CKD enrolled in the Chronic Kidney Disease in Children (CKiD) study. We used linear and logistic regression to analyze the association of plasma FGF23 with left ventricular mass index (LVMI) and LVH (LVMI ≥95th percentile), adjusted for demographics, body mass index, eGFR, and CKD-specific factors. We also examined the relationship between FGF23 and LVH by eGFR level.

RESULTS

Median age was 12 years (interquartile range, 8-15) and eGFR was 50 ml/min per 1.73 m2 (interquartile range, 38-64). Overall prevalence of LVH was 11%. After adjustment for demographics and body mass index, the odds of having LVH was higher by 2.53 (95% confidence interval, 1.28 to 4.97; P<0.01) in participants with FGF23 concentrations ≥170 RU/ml compared with those with FGF23<100 RU/ml, but this association was attenuated after full adjustment. Among participants with eGFR≥45 ml/min per 1.73 m2, the prevalence of LVH was 5.4%, 11.2%, and 15.3% for those with FGF23 <100 RU/ml, 100-169 RU/ml, and ≥170 RU/ml, respectively (Ptrend=0.01). When eGFR was ≥45 ml/min per 1.73 m2, higher FGF23 concentrations were independently associated with LVH (fully adjusted odds ratio, 3.08 in the highest versus lowest FGF23 category; 95% confidence interval, 1.02 to 9.24; P<0.05; fully adjusted odds ratio, 2.02 per doubling of FGF23; 95% confidence interval, 1.29 to 3.17; P<0.01). By contrast, in participants with eGFR<45 ml/min per 1.73 m2, FGF23 did not associate with LVH.

CONCLUSIONS

Plasma FGF23 concentration ≥170 RU/ml is an independent predictor of LVH in children with eGFR≥45 ml/min per 1.73 m2.

Waist Circumference and Body Mass Index in Children with Chronic Kidney Disease and Metabolic, Cardiovascular, and Renal Outcomes

OBJECTIVE

To describe the prevalence of obesity as estimated by waist circumference (WC) and body mass index (BMI) and compare associations of WC and BMI with indicators of metabolic, cardiovascular, and renal health in children with chronic kidney disease (CKD).

STUDY DESIGN

Cross-sectional analysis stratified by CKD etiology (nonglomerular or glomerular) of 737 subjects. The kappa statistic was used to assess agreement between the 2 measures of obesity. Linear regression models were performed using WC and BMI as separate independent variables. Dependent variables included lipid measures, insulin resistance, blood pressure, left ventricular mass index, proteinuria, and estimated glomerular filtration rate. Associations were scaled to SD and interpreted as the change in dependent variable associated with a 1-SD change in WC or BMI.

RESULTS

There was good agreement (kappa statistic = 0.68) between WC and BMI in identifying obesity. Approximately 10% of subjects had obesity by 1 measure but not the other. BMI was more strongly associated with estimated glomerular filtration rate than WC. BMI was more strongly associated with left ventricular mass index in the nonglomerular CKD group compared with WC, but both had significant associations. The associations between WC and BMI with the remainder of the dependent variables were not significantly different.

CONCLUSIONS

Measurement of WC added limited information to BMI in this cohort. Further longitudinal study is needed to determine how WC and BMI compare in predicting outcomes, particularly for children with CKD identified as having obesity by 1 measure but not the other.

Associations Between Weight Loss, Kidney Function Decline, and Risk of ESRD in the Chronic Kidney Disease in Children (CKiD) Cohort Study

BACKGROUND

Anorexia and malnutrition are associated with poor outcomes in children with chronic kidney disease (CKD).

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

We assessed changes in body mass index (BMI) as kidney function declines and its association with risk for end-stage renal disease (ESRD) among 854 participants followed between 2005 to 2013 in the CKD in Children (CKiD) Study.

PREDICTORS

Repeated measurements of estimated glomerular filtration rate (eGFR) by serum creatinine concentration in our trajectory analysis using mixed models; change in BMI z score (per year) after eGFR decreased to <35mL/min/1.73m² in logistic regression models.

OUTCOMES

Repeated measurements of BMI z score (as a reflection of weight status) in our trajectory analysis; ESRD in logistic regression models.

RESULTS

During a mean longitudinal follow-up of 3.4 years, BMI z scores remained stable until eGFR decreased to <35mL/min/1.73m². When eGFR decreased to <35mL/min/1.73m², a mean decline in BMI z score of 0.13 (95% CI, 0.09-0.17) was noted with each 10-mL/min/1.73m² further decline in eGFR. This was statistically significantly different from the weight trajectory when eGFR was ≥35mL/min/1.73 m² (P<0.001). Among children and adolescents with significant weight loss (defined as decline in BMI z score > 0.2 per year) after eGFR decreased to <35mL/min/1.73m², the odds of ESRD was 3.28 (95% CI, 1.53-7.05) times greater compared with participants with stable BMI z scores (BMI z score change per year of 0-0.1).

LIMITATIONS

Observational nature of our study, lack of longitudinal assessments of inflammatory markers.

CONCLUSIONS

In children and adolescents with CKD, weight loss mostly occurs when eGFR decreases to <35mL/min/1.73m², and this weight loss was associated with higher risk for ESRD. Further studies are needed to define the reasons for the association between weight loss and more rapid progression to ESRD in children and adolescents.

Obesity and kidney disease: Hidden consequences of the epidemic

No Abstract Available.

Cognitive Function in Children with Lupus Nephritis: A Cross-Sectional Comparison with Children with Other Glomerular Chronic Kidney Diseases

OBJECTIVE

To identify factors contributing to cognitive impairment in children with lupus nephritis.

STUDY DESIGN

A cross-sectional analysis of a large multicenter national cohort of children with chronic kidney disease (CKD) using standardized measures to determine baseline neuropsychiatric function and health-related quality of life (HRQoL) in children with lupus nephritis (n = 34), and to compare baseline function with that in children with other forms of glomerular CKD (gCKD; n = 171). We used inverse probability weighting via a logistic model for propensity score analysis to achieve balance between children with lupus nephritis and those with other glomerular causes of CKD, adjusting for known confounders. We used linear regression models to compare neurocognitive outcomes between exposure groups, adjusting for current prednisone use and testing for an interaction between current prednisone use and lupus nephritis, and to test for an association between cognitive function and HRQoL.

RESULTS

Current prednisone use was independently associated with worse attention (P < .01) and better adaptive skills (P = .04), and there was a significant interaction between current prednisone use and lupus nephritis for internalizing problems, with worse parent-reported internalizing problems in children with lupus nephritis on prednisone (P = .047). Better parent-reported HRQoL was associated with better visual memory (P = .01), and better child-reported HRQoL was associated with better attention (P < .01) and inhibitory control (P < .01). Both parent and child HRQoL were associated with better measures of executive function (P = .02 and < .001, respectively).

CONCLUSION

Children with lupus nephritis have comparable or better cognitive function than their peers with other gCKDs, which is reassuring given the multiorgan and lifelong complications associated with lupus.

The association between creatinine versus cystatin C-based eGFR and cardiovascular risk in children with chronic kidney disease using a modified PDAY risk score

BACKGROUND

Children with chronic kidney disease (CKD) have a high prevalence of cardiovascular disease (CVD) risk factors which may contribute to the development of cardiovascular events in adulthood. Among adults with CKD, cystatin C-based estimates of glomerular filtration rate (eGFR) demonstrate a stronger predictive value for cardiovascular events than creatinine-based eGFR. The PDAY (Pathobiological Determinants of Atherosclerosis in Youth) risk score is a validated tool used to estimate the probability of advanced coronary atherosclerotic lesions in young adults.

OBJECTIVE

To assess the association between cystatin C-based versus creatinine-based eGFR (eGFR cystatin C and eGFR creatinine, respectively) and cardiovascular risk using a modified PDAY risk score as a proxy for CVD in children and young adults.

METHODS

We performed a cross-sectional study of 71 participants with CKD [median age 15.5 years; inter-quartile range (IQR) 13, 17], and 33 healthy controls (median age 15.1 years; IQR 13, 17). eGFR was calculated using age-appropriate creatinine- and cystatin C-based formulas. Median eGFR creatinine and eGFR cystatin C for CKD participants were 50 (IQR 30, 75) and 53 (32, 74) mL/min/1.73 m², respectively. For the healthy controls, median eGFR creatinine and eGFR cystatin were 112 (IQR 85, 128) and 106 mL/min/1.73m² (95, 123) mL/min/1.73 m², respectively. A modified PDAY risk score was calculated based on sex, age, serum lipoprotein concentrations, obesity, smoking status, hypertension, and hyperglycemia.

RESULTS

Modified PDAY scores ranged from -2 to 20. The Spearman's correlations of eGFR creatinine and eGFR cystatin C with coronary artery PDAY scores were -0.23 (p = 0.02) and -0.28 (p = 0.004), respectively. Ordinal logistic regression also showed a similar association of higher eGFR creatinine and higher eGFR cystatin C with lower PDAY scores. When stratified by age <18 or ≥18 years, the correlations of eGFR creatinine and eGFR cystatin C with PDAY score were modest and similar in children [-0.29 (p = 0.008) vs. -0.32 (p = 0.004), respectively]. Despite a smaller sample size, the correlation in adults was stronger for eGFR cystatin C (-0.57; p = 0.006) than for eGFR creatinine (-0.40; p = 0.07).

CONCLUSIONS

Overall, the correlation between cystatin C- or creatinine-based eGFR with PDAY risk score was similar in children. Further studies in children with CKD should explore the association between cystatin C and cardiovascular risk.

Short, frequent, 5-days-per-week, in-center hemodialysis versus 3-days-per week treatment: a randomized crossover pilot trial through the Midwest Pediatric Nephrology Consortium

BACKGROUND

No controlled trials in children with end-stage kidney disease have assessed the benefits of more frequently administered hemodialysis (HD).

METHODS

We conducted a multicenter, crossover pilot trial to determine if short, more frequent (5 days per week) in-center HD was feasible and associated with improvements in blood pressure compared with three conventional HD treatments per week. Because adult studies have not controlled for the weekly duration of dialysis, we fixed the total treatment time at 12 h a week of dialysis during two 3-month study periods; only frequency varied from 5 to 3 days per week between study periods.

RESULTS

Eight children (median age 16.7 years) consented at three children's hospitals. The prespecified primary composite outcome was a sustained 10% decrease in systolic blood pressure and/or a decrease in antihypertensive medications relative to each study period's baseline. Among the six patients completing both study periods, five (83.3%) experienced the primary outcome during HD performed 5 days per week but not 3 days per week; one of the six (16.7%) achieved that outcome during 3-day but not 5-day (p = 0.22) per week HD. During 5-day HD, all patients had significantly more treatments during which their pre-HD systolic (p = 0.01) or diastolic (p = 0.01) blood pressure was 10% lower than baseline.

CONCLUSIONS

We observed that more frequent HD sessions per week was feasible and associated with improved blood pressure control, but barriers to changing thrice-weekly standard of care include financial reimbursement and the time demands associated with more frequent treatments.

Dietary sources of energy and nutrient intake among children and adolescents with chronic kidney disease

BACKGROUND

Our purpose was to identify the main food contributors to energy and nutrient intake in children with chronic kidney disease (CKD).

METHODS

In this cross-sectional study of dietary intake assessed using Food Frequency Questionnaires (FFQ) in the Chronic Kidney Disease in Children (CKiD) cohort study, we estimated energy and nutrient intake and identified the primary contributing foods within this population.

RESULTS

Completed FFQs were available for 658 children. Of those, 69.9% were boys, median age 12 (interquartile range (IQR) 8-15 years). The average daily energy intake was 1968 kcal (IQR 1523-2574 kcal). Milk was the largest contributor to total energy, protein, potassium, and phosphorus intake. Fast foods were the largest contributors to fat and sodium intake, the second largest contributors to energy intake, and the third largest contributors to potassium and phosphorus intake. Fruit contributed 12.0%, 8.7%, and 6.7% to potassium intake for children aged 2-5, 6-13, and 14-18 years old, respectively.

CONCLUSIONS

Children with CKD consumed more sodium, protein, and calories but less potassium than recommended by the National Kidney Foundation (NKF) guidelines for pediatric CKD. Energy, protein, and sodium intake is heavily driven by consumption of milk and fast foods. Limiting contribution of fast foods in patients with good appetite may be particularly important for maintaining recommended energy and sodium intake, as overconsumption can increase the risk of obesity and cardiovascular complications in that population.

Albuminuria, Proteinuria, and Renal Disease Progression in Children with CKD

BACKGROUND AND OBJECTIVES

The role of albuminuria as an indicator of progression has not been investigated in children with CKD in the absence of diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Children were enrolled from 49 centers of the CKD in Children study between January of 2005 and March of 2014. Cross-sectional multivariable linear regression (n=647) was used to examine the relationship between urine protein-to-creatinine (UP/C [milligrams per milligram]) and albumin-to-creatinine (ACR [milligrams per gram]) with eGFR (milliliters per minute per 1.73 m2). Parametric time-to-event analysis (n=751) was used to assess the association of UP/C, ACR, and urine nonalbumin-to-creatinine (Unon-alb/cr [milligrams per gram]) on the time to the composite endpoint of initiation of RRT or 50% decline in eGFR.

RESULTS

The median follow-up time was 3.4 years and 202 individuals experienced the event. Participants with a UP/C≥0.2 mg/mg and ACR≥30 mg/g had a mean eGFR that was 16 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. Individuals with ACR<30 mg/g, but a UP/C≥0.2 mg/mg, had a mean eGFR that was 9.3 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. When categories of ACR and Unon-alb/cr were created on the basis of clinically meaningful cutoff values of UP/C with the same sample sizes for comparison, the relative times (RTs) to the composite end-point were almost identical when comparing the middle (RT=0.31 for UP/C [0.2-2.0 mg/mg], RT=0.38 for ACR [56-1333 mg/g], RT=0.31 for Unon-alb/cr [118-715 mg/g]) and the highest (RT=0.08 for UP/C [>2.0 mg/mg], RT=0.09 for ACR [>1333 mg/g], RT=0.07 for Unon-alb/cr [>715 mg/g]) levels to the lowest levels. A similar trend was seen when categories were created on the basis of clinically meaningful cutoff values of ACR (<30, 30-300, >300 mg/g).

CONCLUSIONS

In children with CKD without diabetes, the utility of an initial UP/C, ACR, and Unon-alb/cr for characterizing progression is similar.

Relationships of Measured Iohexol GFR and Estimated GFR With CKD-Related Biomarkers in Children and Adolescents

BACKGROUND

2 valid and reliable estimated glomerular filtration rate (GFR) equations for the pediatric population have been developed from directly measured GFR data in the Chronic Kidney Disease in Children (CKiD) cohort: the full CKiD and bedside CKiD equations. Although adult GFR estimating equations replicate relationships of measured GFR with biomarkers, it is unclear whether similar patterns exist among children and adolescents with chronic kidney disease (CKD).

STUDY DESIGN

Prospective cohort study in children and adolescents.

SETTINGS & PARTICIPANTS

730 participants contributed 1,539 study visits.

PREDICTORS

Measured GFR by plasma iohexol disappearance (mGFR), estimated GFR by the full CKiD equation (eGFR_CKiDfull; based on serum creatinine, cystatin C, serum urea nitrogen, height, and sex), and estimated GFR by the bedside CKiD equation (eGFR_CKiDbed; calculated as 41.3 × height [m]/serum creatinine [mg/dL]) were predictors of CKD-related biomarkers. Deviations of mGFR from eGFR_CKiDfull and deviations of eGFR_CKiDfull from eGFR_CKiDbed from linear regressions (ie, residuals) were included in bivariate analyses.

OUTCOMES & MEASUREMENTS

CKD-related biomarkers included values for urine protein-creatinine ratio, blood hemoglobin, serum phosphate, bicarbonate, potassium, systolic and diastolic blood pressure z scores, and height z scores.

RESULTS

The median age of 730 participants with CKD was 12.5 years, with median mGFR, eGFR_CKiDfull, and eGFR_CKiDbed of 51.8, 54.0, and 53.2mL/min/1.73m², respectively. eGFR_CKiDfull demonstrated as strong or stronger associations with CKD-related biomarkers than mGFR; eGFR_CKiDbed associations were significantly attenuated (ie, closer to the null). Residual information in mGFR did not substantially increase explained variability. eGFR_CKiDbed estimated faster GFR decline relative to mGFR and eGFR_CKiDfull.

LIMITATIONS

Simple linear summaries of biomarkers may not capture nonlinear associations.

CONCLUSIONS

eGFR_CKiDfull closely approximated mGFR to describe relationships with CKD-severity indicators and progression in this pediatric CKD population. eGFR_CKiDbed offered similar inferences, but associations were attenuated and rate of progression was overestimated. The eGFR_CKiDfull equation from 2012 is preferred for pediatric research purposes.

Pilot study of the effect of cholecalciferol supplementation on hepcidin in children with chronic kidney disease: Results of the D-fense Trial

BACKGROUND

Hepcidin is a key mediator of the anemia of chronic kidney disease (CKD). There is emerging evidence that 25-hydroxyvitamin D (25D) regulates hepcidin production.

METHODS

A randomized controlled trial of daily vitamin D supplementation for 12 weeks was performed with the aim to test the effects of 4000 versus 400 IU of cholecalciferol on serum hepcidin levels in children with non-dialysis CKD recruited at a tertiary care children's hospital. Hepcidin was quantified using a validated competitive enzyme-linked immunosorbent assay. 25D levels were measured using the chemiluminescence Liaison 25(OH)D assay system. Co-variables included hemoglobin, C-reactive protein, ferritin, and serum calcium and phosphorus for safety monitoring.

RESULTS

A total of 34 subjects were randomized to either the intervention or control group, of whom 26.5% were female and 23.5% were African American. The mean age of the study cohort was 10.9 [standard deviation (SD) 5.8] years, the mean baseline glomerular filtration rate was 60 (SD 17.6) ml/min/1.73 m², and mean baseline 25D level was 29.7 (SD 11.5) ng/ml. At baseline, 50% of subjects were 25D deficient. There were no significant differences in baseline characteristics between the intervention and control groups. Treatment with 4000 IU cholecalciferol was not associated with significant change in hepcidin level at 4 or 12 weeks, and multivariable generalized estimating equation regression demonstrated no significant difference in change in hepcidin over the treatment period in either arm. The median C-reactive protein level decreased significantly at 12 weeks in the intervention group.

CONCLUSIONS

These results do not suggest that daily nutritional vitamin D supplementation modifies serum hepcidin levels in children with CKD. Further study will be required to determine whether supplementation may be effective in children with more advanced CKD or those on dialysis.

Dietary Zinc and Incident Calcium Kidney Stones in Adolescence

PURPOSE

We determined the association between dietary zinc intake and incident calcium kidney stones in adolescents. We also examined the relationship between dietary zinc intake and urinary zinc excretion between cases and controls.

MATERIALS AND METHODS

We conducted a nested case-control study within a large pediatric health care system. Three 24-hour dietary recalls and spot urine chemistry analyses were obtained for 30 participants 12 to 18 years old with a first idiopathic calcium based kidney stone and 30 healthy controls matched for age, sex, race and month of enrollment. Conditional logistic regression models were used to estimate the association between daily zinc intake and incident calcium kidney stones, adjusting for dietary phytate, protein, calcium, sodium and oxalate. Multivariable linear regression was used to estimate the association between dietary and urine zinc, adjusting for urine creatinine and dietary phytate and calcium.

RESULTS

Cases had lower daily zinc intake (8.1 mg) than controls (10 mg, p = 0.029). Daily zinc intake of boys and girls with calcium stones was 2 mg and 1.2 mg less, respectively, than the daily intake recommended by the Institute of Medicine. Odds of incident stones were reduced by 13% for every 1 mg increase in daily zinc intake (OR 0.87, 95% CI 0.75-0.99). There was an estimated 4.5 μg/dl increase in urine zinc for every 1 mg increase in dietary zinc (p = 0.009), with weak evidence of a smaller increase in urine zinc in cases than in controls (interaction p = 0.08).

CONCLUSIONS

Decreased dietary zinc intake was independently associated with incident calcium nephrolithiasis in this population of adolescents.

Obesity and kidney disease: hidden consequences of the epidemic

Obesity has become a worldwide epidemic and its prevalence has been projected to grow by 40% in the next decade. This increasing prevalence has implications for the risk of diabetes, cardiovascular disease and also for chronic kidney disease (CKD). A high body mass index is one of the strongest risk factors for new-onset CKD. In individuals affected by obesity, a compensatory hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight. The increase in intraglomerular pressure can damage the kidneys and raise the risk of developing CKD in the long-term. The incidence of obesity-related glomerulopathy has increased ten-fold in recent years. Obesity has also been shown to be a risk factor for nephrolithiasis, and for a number of malignancies including kidney cancer. This year, the World Kidney Day will promote education on the harmful consequences of obesity and its association with kidney disease, advocating healthy lifestyle and health policy measures that make preventive behaviors an affordable option.

Vascular Stiffness in Children With Chronic Kidney Disease

Carotid-femoral pulse wave velocity (cfPWV) is a measure of arterial stiffness associated with cardiovascular events in the general population and in adults with chronic kidney disease. However, few data exist regarding cfPWV in children with chronic kidney disease. We compared observed cfPWV assessed via applanation tonometry in children enrolled in the CKiD cohort study (Chronic Kidney Disease in Children) to normative data in healthy children and examined risk factors associated with elevated cfPWV. cfPWV Z score for height/gender and age/gender was calculated from and compared with published pediatric norms. Multivariable linear regression was used to assess the relationship between cfPWV and age, gender, race, body mass index, diagnosis, urine protein-creatinine ratio, mean arterial pressure, heart rate, number of antihypertensive medications, uric acid, and serum low-density lipoprotein. Of the 95 participants with measured cfPWV, 60% were male, 19% were black, 46% had glomerular cause of chronic kidney disease, 22% had urine protein-creatinine ratio 0.5 to 2.0 mg/mg and 9% had >2.0 mg/mg, mean age was 15.1 years, average mean arterial pressure was 80 mm Hg, and median glomerular filtration rate was 63 mL/min per 1.73 m² Mean cfPWV was 5.0 m/s (SD, 0.8 m/s); mean cfPWV Z score by height/gender norms was -0.1 (SD, 1.1). cfPWV increased significantly with age, mean arterial pressure, and black race in multivariable analysis; no other variables, including glomerular filtration rate, were independently associated with cfPWV. In this pediatric cohort with mild kidney dysfunction, arterial stiffness was comparable to that of normal children. Future research is needed to examine the impact of chronic kidney disease progression on arterial stiffness and associated cardiovascular parameters in children.

Renin-angiotensin II-aldosterone system blockers and time to renal replacement therapy in children with CKD

BACKGROUND

Clinical care decisions to treat chronic kidney disease (CKD) in a growing child must often be made without the benefit of evidence from clinical trials. We used observational data from the Chronic Kidney Disease in Children cohort to estimate the effectiveness of renin-angiotensin II-aldosterone system blockade (RAAS) to delay renal replacement therapy (RRT) in children with CKD.

METHODS

A total of 851 participants (median age: 11 years, median glomerular filtration rate [GFR]: 52 ml/min/1.73 m2, median urine protein to creatinine ratio: 0.35 mg/mg) were included. RAAS use was reported at annual study visits. Both Cox proportional hazards models with time-varying RAAS exposure and Cox marginal structural models (MSM) were used to evaluate the effect of RAAS use on time to RRT. Analyses were adjusted or weighted to control for age, male sex, glomerular diagnosis, GFR, nephrotic range proteinuria, anemia, elevated blood pressure, acidosis, elevated phosphate and elevated potassium.

RESULTS

There were 217 RRT events over a 4.1-year median follow-up. At baseline, 472 children (55 %) were prevalent RAAS users, who were more likely to be older, have a glomerular etiology, have higher urine protein, be anemic, have elevated serum phosphate and potassium, take more medications, but less likely to have elevated blood pressure, compared with non-users. RAAS use was found to reduce the risk of RRT by 21 % (hazard ratio: 0.79) to 37 % (hazard ratio: 0.63) from standard regression adjustment and MSM models, respectively.

CONCLUSIONS

These results support inferences from adult studies of a substantial benefit of RAAS use in pediatric CKD patients.

Genomic Disorders and Neurocognitive Impairment in Pediatric CKD

Children with CKD are at increased risk for neurocognitive impairment, but whether neurocognitive dysfunction is solely attributable to impaired renal function is unclear. Data from the CKD in Children Study Chronic Kidney Disease in Children (CKiD) Study indicate that a subset of children with CKD have unsuspected genomic disorders that predispose them to organ malformations and neurocognitive impairment. We therefore tested whether the CKiD Study participants with genomic disorders had impaired neurocognitive performance at enrollment. Compared with noncarriers (n=389), children with genomic disorders (n=31) scored significantly poorer on all measures of intelligence, anxiety/depressive symptoms, and executive function (differences of 0.6-0.7 SD; P=1.2×10^-3-2.4×10^-4). These differences persisted after controlling for known modifiers, including low birth weight, maternal education, seizure disorder, kidney disease duration, and genetically defined ancestry. The deleterious effect of genomic disorders on neurocognitive function was significantly attenuated in offspring of mothers with higher education, indicating the potential for modification by genetic and/or environmental factors. These data indicate that impaired neurocognitive function in some children with CKD may be attributable to genetic lesions that affect both kidney and neurocognitive development. Early identification of genomic disorders may provide opportunity for early diagnosis and personalized interventions to mitigate the effect on neurocognitive function.

Obesity and Kidney Disease: Hidden Consequences of the Epidemic

Obesity has become a worldwide epidemic, and its prevalence has been projected to grow by 40% in the next decade. This increasing prevalence has implications for the risk of diabetes, cardiovascular disease, and also for chronic kidney disease (CKD). A high body mass index is one of the strongest risk factors for new-onset CKD. In individuals affected by obesity, a compensatory hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight. The increase in intraglomerular pressure can damage the kidneys and raise the risk of developing CKD in the long term. The incidence of obesity-related glomerulopathy has increased 10-fold in recent years. Obesity has also been shown to be a risk factor for nephrolithiasis, and for a number of malignancies including kidney cancer. This year the World Kidney Day promotes education on the harmful consequences of obesity and its association with kidney disease, advocating healthy lifestyle and health policy measures that make preventive behaviors an affordable option.

Assessment of dietary intake of children with chronic kidney disease

OBJECTIVE

Our aim was to characterize the nutrient intake of children with chronic kidney disease (CKD) relative to recommended intake levels.

METHODS

We conducted a cross-sectional study of dietary intake assessed by Food Frequency Questionnaire (FFQ) in The North American Chronic Kidney Disease in Children (CKiD) prospective cohort study. Nutrient intake was analyzed to estimate the daily consumption levels of various nutrients and compared with national guidelines for intake.

RESULTS

There were 658 FFQs available for analysis; 69.9 % of respondents were boys, with a median age [Interquartile range (IQR)] of 11 years (8-15). Median daily sodium, potassium, and phosphorus intake was 3089 mg (2294-4243), 2384 mg (1804-3076), and 1206 mg (894-1612) respectively. Sodium and phosphorus consumptions were higher than recommended in all age groups. Caloric intake decreased with dropping glomerular filtration rate (GFR) (p = 0.003). The median daily caloric intakes were 1307 kcal in male children 2-3 years old, 1875 kcal in children 4-8 years old, 1923 kcal in those 9-13 years old, and 2427 kcal in those 14-18 years old. Respective levels for girls were 1467 kcal, 1736 kcal, 1803 kcal, and 2281 kcal. Median protein intake exceeded recommended levels in all age groups, particularly among younger participants. Younger children were more likely than older children to exceed the recommended intakes for phosphorus (p < 0.001) and the age-specific recommended caloric intake (p < 0.001). Macronutrient distribution (carbohydrate:fat:protein) was consistent with recommendation.

CONCLUSIONS

Children in the CKiD cohort consumed more sodium, phosphorus, protein, and calories than recommended. The gap between actual consumption and recommendations indicates a need for improved nutritional counseling and monitoring.