Longitudinal Relationship Between Anemia and Statural Growth Impairment in Children and Adolescents With Nonglomerular CKD: Findings From the Chronic Kidney Disease in Children (CKiD) Study

RATIONALE & OBJECTIVE

Anemia and statural growth impairment are both prevalent in children with nonglomerular chronic kidney disease (CKD) and are associated with poor quality of life and increased morbidity and mortality. However, to date no longitudinal studies have demonstrated a relationship between anemia and statural growth in this population.

STUDY DESIGN

The CKD in Children (CKiD) study is a multicenter prospective cohort study with over 15 years of follow-up observation.

SETTING & PARTICIPANTS

CKiD participants younger than 22 years with nonglomerular CKD who had not reached final adult height.

EXPOSURE

Age-, sex-, and race-specific hemoglobin z score.

OUTCOME

Age- and sex-specific height z score.

ANALYTICAL APPROACH

The relationship between hemoglobin and height was quantified using (1) multivariable repeated measures paired person-visit analysis, and (2) multivariable repeated measures linear mixed model analysis. Both models were adjusted for age, sex, body mass index, estimated glomerular filtration rate, acidosis, and medication use.

RESULTS

Overall, 67% of the 510 participants studied had declining hemoglobin z score trajectories over the follow-up period, which included 1,763 person-visits. Compared with average hemoglobin z scores of≥0, average hemoglobin z scores of less than -1.0 were independently associated with significant growth impairment at the subsequent study visit, with height z score decline ranging from 0.24 to 0.35. Importantly, in 50% of cases hemoglobin z scores of less than -1.0 corresponded to hemoglobin values higher than those used as cutoffs defining anemia in the KDIGO clinical practice guideline for anemia in CKD. When stratified by age, the magnitude of the association peaked in participants aged 9 years. In line with paired-visit analyses, our mixed model analysis demonstrated that in participants with baseline hemoglobin z score less than -1.0, a hemoglobin z score decline over the follow-up period was associated with a statistically significant concurrent decrease in height z score.

LIMITATIONS

Limited ability to infer causality.

CONCLUSIONS

Hemoglobin decline is associated with growth impairment over time in children with mild to moderate nonglomerular CKD, even before hemoglobin levels reach the cutoffs that are currently used to define anemia in this population.

Associations of body mass index (BMI) and BMI change with progression of chronic kidney disease in children

BACKGROUND

Obesity is prevalent among children with chronic kidney disease (CKD) and is associated with cardiovascular disease and reduced quality of life. Its relationship with pediatric CKD progression has not been described.

METHODS

We evaluated relationships between both body mass index (BMI) category (normal, overweight, obese) and BMI z-score (BMIz) change on CKD progression among participants of the Chronic Kidney Disease in Children study. Kaplan-Meier survival curves and multivariable parametric failure time models depict the association of baseline BMI category on time to kidney replacement therapy (KRT). Additionally, the annualized percentage change in estimated glomerular filtration rate (eGFR) was modeled against concurrent change in BMIz using multivariable linear regression with generalized estimating equations which allowed for quantification of the effect of BMIz change on annualized eGFR change.

RESULTS

Participants had median age of 10.9 years [IQR: 6.5, 14.6], median eGFR of 50 ml/1.73 m2 [IQR: 37, 64] and 63% were male. 160 (27%) of 600 children with non-glomerular and 77 (31%) of 247 children with glomerular CKD progressed to KRT over a median of 5 years [IQR: 2, 8]. Times to KRT were not significantly associated with baseline BMI category. Children with non-glomerular CKD who were obese experienced significant improvement in eGFR (+ 0.62%; 95% CI: + 0.17%, + 1.08%) for every 0.1 standard deviation concurrent decrease in BMI. In participants with glomerular CKD who were obese, BMIz change was not significantly associated with annualized eGFR change.

CONCLUSION

Obesity may represent a target of intervention to improve kidney function in children with non-glomerular CKD. A higher resolution version of the Graphical abstract is available as Supplementary information.

Abstract P212: Plasma Metabolomics of Dietary Intake of Protein-Rich Foods and Kidney Disease Progression in Children

Introduction: There is inconsistent evidence on the efficacy of a low-protein diet for patients with chronic kidney disease (CKD) and there is a lack of objective biomarkers of dietary intake. The purpose of this study was to identify plasma metabolites associated with dietary intake of protein among children with CKD and to assess whether protein-related metabolites are associated with CKD progression.

Methods: We conducted non-targeted metabolomics using plasma samples from 484 Chronic Kidney Disease in Children (CKiD) participants. Multivariable linear regression estimated the cross-sectional association between 949 known, non-drug metabolites and dietary intake of dairy, nuts and beans, red and processed meat, fish, chicken, and eggs, adjusting for demographic, clinical, and dietary covariates. Cox proportional hazards regression models assessed the prospective association between protein-related metabolites and CKD progression defined as kidney replacement therapy or 50% eGFR reduction, adjusting for demographic and clinical covariates. We used a false discovery rate <0.05 as the statistical significance threshold to account for multiple comparisons.

Results: Fifty-seven unique metabolites were significantly associated with dietary protein intake (dairy: n=21; nuts and beans: n=13; red and processed meat: n=20; fish: n=2; chicken: n=3; eggs: n=0). Among them, ten metabolites were significantly associated with CKD progression (TABLE) , including one amino acid, one cofactor and vitamin, four lipids, two nucleotides, one peptide, and one xenobiotic. 1-(1-enyl-palmitoyl)-2-oleoyl-GPE (P-16:0/18:1) was positively associated with dietary intake of red and processed meat and CKD progression, and 3-ureidopropionate was inversely associated with dietary intake of red and processed meat and CKD progression.

Conclusion: Untargeted plasma metabolomic profiling revealed metabolites associated with dietary intake of protein and CKD progression in a pediatric population.

Longitudinal changes in uric acid concentration and their relationship with chronic kidney disease progression in children and adolescents

BACKGROUND

Elevated serum uric acid concentration is a risk factor for CKD progression. Its change over time and association with CKD etiology and concomitant changes in estimated glomerular filtration rate (eGFR) in children and adolescents are unknown.

METHODS

Longitudinal study of 153 children/adolescents with glomerular (G) and 540 with non-glomerular (NG) etiology from the CKD in Children (CKiD) study. Baseline serum uric acid, change in uric acid and eGFR over time, CKD etiology, and comorbidities were monitored. Adjusted linear mixed-effects regression models quantified the relationship between within-person changes in uric acid and concurrent within-person changes in eGFR.

RESULTS

Participants with stable uric acid over follow-up had CKD progression which became worse for increased baseline uric acid (average annual percentage changes in eGFR were - 1.4%, - 7.7%, and - 14.7% in those with G CKD with baseline uric acid < 5.5 mg/dL, 5.5 - 7.5 mg/dL, and > 7.5 mg/dL, respectively; these changes were - 1.4%, - 4.1%, and - 8.6% in NG CKD). Each 1 mg/dL increase in uric acid over follow-up was independently associated with significant concomitant eGFR decreases of - 5.7% (95%CI - 8.4 to - 3.0%) (G) and - 5.1% (95%CI - 6.3 to - 4.0%) (NG) for those with baseline uric acid < 5.5 mg/dL and - 4.3% (95%CI - 6.8 to - 1.6%) (G) and - 3.3% (95%CI - 4.1 to - 2.6%) (NG) with baseline uric acid between 5.5 and 7.5 mg/dL.

CONCLUSIONS

Higher uric acid levels and increases in uric acid over time are risk factors for more severe progression of CKD in children and adolescents. A higher resolution version of the Graphical abstract is available as Supplementary information.

Evaluating Kidney Function Decline in Children with Chronic Kidney Disease Using a Multi-Institutional Electronic Health Record Database

BACKGROUND

The objectives of this study were to use electronic health record data from a US national multicenter pediatric network to identify a large cohort of children with CKD, evaluate CKD progression, and examine clinical risk factors for kidney function decline.

METHODS

This retrospective cohort study identified children seen between January 1, 2009, to February 28, 2022. Data were from six pediatric health systems in PEDSnet. We identified children aged 18 months to 18 years who met criteria for CKD: two eGFR values <90 and ≥15 ml/min per 1.73 m2 separated by ≥90 days without an intervening value ≥90. CKD progression was defined as a composite outcome: eGFR <15 ml/min per 1.73 m2, ≥50% eGFR decline, long-term dialysis, or kidney transplant. Subcohorts were defined based on CKD etiology: glomerular, nonglomerular, or malignancy. We assessed the association of hypertension (≥2 visits with hypertension diagnosis code) and proteinuria (≥1 urinalysis with ≥1+ protein) within 2 years of cohort entrance on the composite outcome.

RESULTS

Among 7,148,875 children, we identified 11,240 (15.7 per 10,000) with CKD (median age 11 years, 50% female). The median follow-up was 5.1 (interquartile range 2.8-8.3) years, the median initial eGFR was 75.3 (interquartile range 61-83) ml/min per 1.73 m2, 37% had proteinuria, and 35% had hypertension. The following were associated with CKD progression: lower eGFR category (adjusted hazard ratio [aHR] 1.44 [95% confidence interval (95% CI), 1.23 to 1.69], aHR 2.38 [95% CI, 2.02 to 2.79], aHR 5.75 [95% CI, 5.05 to 6.55] for eGFR 45-59 ml/min per 1.73 m2, 30-44 ml/min per 1.73 m2, 15-29 ml/min per 1.73 m2 at cohort entrance, respectively, when compared with eGFR 60-89 ml/min per 1.73 m2), glomerular disease (aHR 2.01 [95% CI, 1.78 to 2.28]), malignancy (aHR 1.79 [95% CI, 1.52 to 2.11]), proteinuria (aHR 2.23 [95% CI, 1.89 to 2.62]), hypertension (aHR 1.49 [95% CI, 1.22 to 1.82]), proteinuria and hypertension together (aHR 3.98 [95% CI, 3.40 to 4.68]), count of complex chronic comorbidities (aHR 1.07 [95% CI, 1.05 to 1.10] per additional comorbid body system), male sex (aHR 1.16 [95% CI, 1.05 to 1.28]), and younger age at cohort entrance (aHR 0.95 [95% CI, 0.94 to 0.96] per year older).

CONCLUSIONS

In large-scale real-world data for children with CKD, disease etiology, albuminuria, hypertension, age, male sex, lower eGFR, and greater medical complexity at start of follow-up were associated with more rapid decline in kidney function.

Evaluation of galectin-3 and intestinal fatty acid binding protein as serum biomarkers in autosomal recessive polycystic kidney disease

BACKGROUND

Autosomal recessive polycystic kidney disease (ARPKD) causes fibrocystic kidney disease, congenital hepatic fibrosis, and portal hypertension. Serum galectin-3 (Gal-3) and intestinal fatty acid binding protein (I-FABP) are potential biomarkers of kidney fibrosis and portal hypertension, respectively. We examined whether serum Gal-3 associates with kidney disease severity and serum I-FABP associates with liver disease severity in ARPKD.

METHODS

Cross-sectional study of 29 participants with ARPKD (0.2-21 years old) and presence of native kidneys (Gal-3 analyses, n = 18) and/or native livers (I-FABP analyses, n = 21). Serum Gal-3 and I-FABP were analyzed using enzyme linked immunosorbent assay. Kidney disease severity variables included estimated glomerular filtration rate (eGFR) and height-adjusted total kidney volume (htTKV). Liver disease severity was characterized using ultrasound elastography to measure liver fibrosis, and spleen length and platelet count as markers of portal hypertension. Simple and multivariable linear regression examined associations between Gal-3 and kidney disease severity (adjusted for liver disease severity) and between I-FABP and liver disease severity (adjusted for eGFR).

RESULTS

Serum Gal-3 was negatively associated with eGFR; 1 standard deviation (SD) lower eGFR was associated with 0.795 SD higher Gal-3 level (95% CI - 1.116, - 0.473; p < 0.001). This association remained significant when adjusted for liver disease severity. Serum Gal-3 was not associated with htTKV in adjusted analyses. Overall I-FABP levels were elevated, but there were no linear associations between I-FABP and liver disease severity in unadjusted or adjusted models.

CONCLUSIONS

Serum Gal-3 is associated with eGFR in ARPKD, suggesting its value as a possible novel biomarker of kidney disease severity. We found no associations between serum I-FABP and ARPKD liver disease severity despite overall elevated I-FABP levels.

Skeletal Outcomes in Children and Young Adults with Glomerular Disease

BACKGROUND

Children with glomerular disease have unique risk factors for compromised bone health. Studies addressing skeletal complications in this population are lacking.

METHODS

This retrospective cohort study utilized data from PEDSnet, a national network of pediatric health systems with standardized electronic health record data for more than 6.5 million patients from 2009 to 2021. Incidence rates (per 10,000 person-years) of fracture, slipped capital femoral epiphysis (SCFE), and avascular necrosis/osteonecrosis (AVN) in 4598 children and young adults with glomerular disease were compared with those among 553,624 general pediatric patients using Poisson regression analysis. The glomerular disease cohort was identified using a published computable phenotype. Inclusion criteria for the general pediatric cohort were two or more primary care visits 1 year or more apart between 1 and 21 years of age, one visit or more every 18 months if followed >3 years, and no chronic progressive conditions defined by the Pediatric Medical Complexity Algorithm. Fracture, SCFE, and AVN were identified using SNOMED-CT diagnosis codes; fracture required an associated x-ray or splinting/casting procedure within 48 hours.

RESULTS

We found a higher risk of fracture for the glomerular disease cohort compared with the general pediatric cohort in girls only (incidence rate ratio [IRR], 1.6; 95% CI, 1.3 to 1.9). Hip/femur and vertebral fracture risk were increased in the glomerular disease cohort: adjusted IRR was 2.2 (95% CI, 1.3 to 3.7) and 5 (95% CI, 3.2 to 7.6), respectively. For SCFE, the adjusted IRR was 3.4 (95% CI, 1.9 to 5.9). For AVN, the adjusted IRR was 56.2 (95% CI, 40.7 to 77.5).

CONCLUSIONS

Children and young adults with glomerular disease have significantly higher burden of skeletal complications than the general pediatric population.

Nocturnal Dipping and Kidney Function Decline: Findings From the CKD in Children Study

Introduction

Normally, blood pressure (BP) declines by at least 10% from daytime to nighttime. In adults, blunted nocturnal dipping has been associated with more rapid decline in kidney function. Nondipping is prevalent in children with chronic kidney disease (CKD). We sought to determine whether nondipping is associated with proteinuria and progression to kidney failure in children with CKD.

Methods

In the prospective CKD in children (CKiD) cohort, Cox proportional hazards models were used to evaluate the relationship between baseline nondipping and progression to kidney failure. Linear mixed effects models were used to evaluate the relationship between nondipping and changes in iohexol glomerular filtration rate (GFR) and urine protein-to-creatinine ratio (log-UPCR, mg/mg) over time.

Results

Among 620 participants, mean age was 11 (± 4) years, mean iohexol GFR was 52 (± 22) ml/min per 1.73 m2, and 40% were nondippers at baseline. There were 169 kidney failure events during 2.9 years (median) of follow-up. Dipping status was not significantly associated with kidney failure overall (hazard ratio [HR] 1.08; 95% confidence interval [CI] 0.77, 1.51) or in those with (HR 1.21; 95% CI 0.53, 2.77) or without (HR 1.05; 95% CI 0.71, 1.55) glomerular disease. Dipping status did not modify the relationship between time and change in iohexol GFR or log (UPCR) from baseline (interaction P values = 0.20 and 0.054, respectively).

Conclusion

Nondipping is not associated with end-stage kidney disease, GFR decline, or change in proteinuria within the CKiD cohort.

Urine Uromodulin Is Not Associated With Blood Pressure in the Chronic Kidney Disease in Children Cohort

BACKGROUND

Uromodulin regulates activity of the sodium-potassium-two-chloride transporter in the loop of Henle. In adults, higher urine uromodulin levels are associated with greater rise in blood pressure (BP) in response to salt intake. We hypothesized that higher urine uromodulin levels would be associated with higher BP in children with chronic kidney disease, and that there would be an interaction of dietary sodium on this association.

METHODS

In the chronic kidney disease in children Cohort, we utilized univariable and multivariable linear regression models to evaluate the relationship between baseline spot urine uromodulin levels indexed to urine creatinine (Umod/Cr mg/g) and 24-hour mean systolic and diastolic BP, as well as baseline clinic BP. We also tested whether sodium intake (g/day) modified these relationships.

RESULTS

Among 436 participants, the median age was 12.4 years (8.9-15.2), median estimated glomerular filtration rate was 50 mL/min per 1.73 m2 (36-62), and median 24-hour mean systolic BP was 112 mm Hg (104-119). The etiology of chronic kidney disease was glomerular disease in 27%. In univariable models, each 2-fold higher Umod/Cr ratio was associated with a 1.66 mm Hg (95% CI, -2.31 to -1.00) lower 24-hour mean systolic and a 1.71 mm Hg (-2.45 to -0.97) lower clinic systolic BP. However, there was no statistically significant association between Umod/Cr and either 24-hour or clinic BP in multivariable models. We did not find a significant interaction between uromodulin and sodium intake in their effect on BP (P>0.05 in all models).

CONCLUSIONS

Urine uromodulin levels are not associated with BP in the chronic kidney disease in children cohort. Further studies are needed to confirm this finding in healthy pediatric cohorts.

Nocturnal Hypertension in Children With Chronic Kidney Disease Is Common and Associated With Progression to Kidney Replacement Therapy

BACKGROUND

Nocturnal hypertension is a risk factor for chronic kidney disease (CKD) progression among adults. In children, effects of nocturnal hypertension on CKD progression is less studied.

METHODS

We investigated the relationships between nocturnal, daytime, or sustained hypertension and progression to kidney replacement therapy in children using Cox proportional hazards models. Nocturnal and diurnal hypertension respectively defined as: mean blood pressure >95th percentile and/or load >25% for either systolic or diastolic blood pressure within sleep or wake periods.

RESULTS

One thousand five hundred seventy-seven ambulatory blood pressure monitoring studies from 701 CKiD participants were reviewed. Nighttime, daytime, and both types of hypertension were 19%, 7%, and 33%, respectively. Participants with both daytime and nocturnal hypertension had the highest risk of kidney replacement therapy. Among children with CKD, compared with those who were normotensive, those with isolated nocturnal hypertension had a hazard ratio of 1.49 ([CI, 0.97-2.28]; P=0.068) while those with both daytime and nocturnal hypertension had a HR of 2.23 ([CI, 1.60-3.11]; P<0.001) when adjusted for age, race, sex, and baseline proteinuria and glomerular filtration. Estimates for risk were similar among glomerular and nonglomerular participants but not significant in glomerular due to smaller sample size.

CONCLUSIONS

The presence of both daytime and nocturnal hypertension is significantly associated with risk of kidney replacement therapy. Our study confirms the utility of ambulatory blood pressure monitoring in children with CKD. Identifying and controlling both daytime and nocturnal hypertension using ambulatory blood pressure monitoring may improve outcomes and delay CKD progression in this population.

Machine Learning-Based Prediction of Masked Hypertension Among Children With Chronic Kidney Disease

BACKGROUND

Ambulatory blood pressure monitoring (ABPM) is routinely performed in children with chronic kidney disease to identify masked hypertension, a risk factor for accelerated chronic kidney disease progression. However, ABPM is burdensome, and developing an accurate prediction of masked hypertension may allow using ABPM selectively rather than routinely.

METHODS

To create a prediction model for masked hypertension using clinic blood pressure (BP) and other clinical characteristics, we analyzed 809 ABPM studies with nonhypertensive clinic BP among the participants of the Chronic Kidney Disease in Children study.

RESULTS

Masked hypertension was identified in 170 (21.0%) observations. We created prediction models for masked hypertension via gradient boosting, random forests, and logistic regression using 109 candidate predictors and evaluated its performance using bootstrap validation. The models showed C statistics from 0.660 (95% CI, 0.595-0.707) to 0.732 (95% CI, 0.695-0.786) and Brier scores from 0.148 (95% CI, 0.141-0.154) to 0.167 (95% CI, 0.152-0.183). Using the possible thresholds identified from this model, we stratified the dataset by clinic systolic/diastolic BP percentiles. The prevalence of masked hypertension was the lowest (4.8%) when clinic systolic/diastolic BP were both <20th percentile, and relatively low (9.0%) with clinic systolic BP<20th and diastolic BP<80th percentiles. Above these thresholds, the prevalence was higher with no discernable pattern.

CONCLUSIONS

ABPM could be used selectively in those with low clinic BP, for example, systolic BP<20th and diastolic BP<80th percentiles, although careful assessment is warranted as masked hypertension was not completely absent even in this subgroup. Above these clinic BP levels, routine ABPM remains recommended.

Perspectives of Clinicians on Shared Decision Making in Pediatric CKD: A Qualitative Study

RATIONALE & OBJECTIVE

Clinical decision-making priorities may differ among children, their parents, and their clinicians. This study describes clinicians' perspectives on shared decision making in pediatric chronic kidney disease (CKD) and identifies opportunities to improve shared decision making and care for children with CKD and their families.

STUDY DESIGN

Semistructured interviews.

SETTING & PARTICIPANTS

Fifty clinicians participated, including pediatric nephrologists, nurses, social workers, surgeons, dietitians, and psychologists involved in providing care to children with CKD. They worked at 18 hospitals and 4 university research departments across 11 countries (United States of America, Canada, Australia, People's Republic of China, United Kingdom, Germany, France, Italy, Lithuania, New Zealand, and Singapore).

ANALYTICAL APPROACH

Interview transcripts were analyzed thematically.

RESULTS

We identified 4 themes: (1) striving to blend priorities (minimizing treatment burden, emphasizing clinical long-term risks, achieving common goals), (2) focusing on medical responsibilities (carrying decisional burden and pressure of expectations, working within system constraints, ensuring safety is foremost concern), (3) collaborating to achieve better long-term outcomes (individualizing care, creating partnerships, encouraging ownership and participation in shared decision making, sensitive to parental distress), and (4) forming cumulative knowledge (balancing reassurance and realistic expectations, building understanding around treatment, harnessing motivation for long-term goals).

LIMITATIONS

Most clinicians were from high-income countries, so the transferability of the findings to other settings is uncertain.

CONCLUSIONS

Clinicians reported striving to minimize treatment burden and working with children and their families to manage their expectations and support their decision making. However, they are challenged with system constraints and sometimes felt the pressure of being responsible for the child's long-term outcomes. Further studies are needed to test whether support for shared decision making would promote strategies to establish and improve the quality of care for children with CKD.

The Relationship Between Neighborhood Disadvantage and Kidney Disease Progression in the Chronic Kidney Disease in Children (CKiD) Cohort

RATIONALE & OBJECTIVE

To examine the relationship between neighborhood poverty and deprivation, chronic kidney disease (CKD) comorbidities, and disease progression in children with CKD.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

Children with mild to moderate CKD enrolled in the CKiD (Chronic Kidney Disease in Children) study with available US Census data.

EXPOSURE

Neighborhood poverty and neighborhood disadvantage.

OUTCOME

Binary outcomes of short stature, obesity, hypertension, and health care utilization for cross-sectional analysis; a CKD progression end point (incident kidney replacement therapy [KRT] or 50% loss in estimated glomerular filtration rate), and mode of first KRT for time-to-event analysis.

ANALYTICAL APPROACH

Cross-sectional analysis of health characteristics at time of first Census data collection using logistic regression to estimate odds ratios. Risk for CKD progression was analyzed using a Cox proportional hazard model. Multivariable models were adjusted for race, ethnicity, sex, and family income.

RESULTS

There was strong agreement between family and neighborhood socioeconomic characteristics. Risk for short stature, hospitalization, and emergency department (ED) use were significantly associated with lower neighborhood income. After controlling for race, ethnicity, sex, and family income, the odds of hospitalization (OR, 1.71 [95% CI, 1.08-2.71]) and ED use (OR, 1.56 [95% CI, 1.02-2.40]) remained higher for those with lower neighborhood income. The hazard ratio of reaching the CKD progression outcome for participants living in lower income neighborhoods was significantly increased in the unadjusted model only (1.38 [95% CI, 1.02-1.87]). Likelihood of undergoing a preemptive transplant was decreased with lower neighborhood income (OR, 0.47 [95% CI, 0.24-0.96]) and higher neighborhood deprivation (OR, 0.31 [95% CI, 0.10-0.97]), but these associations did not persist after controlling for participant characteristics.

LIMITATIONS

Limited generalizability, as only those with consistent longitudinal nephrology care were studied.

CONCLUSIONS

Neighborhood-level socioeconomic status (SES) was associated with poorer health characteristics and CKD progression in univariable analysis. However, the relationships were attenuated after accounting for participant-level factors including race. A persistent association of neighborhood poverty with hospitalizations and ED suggests an independent effect of SES on health care utilization, the causes for which deserve additional study.

Self-reported Race, Serum Creatinine, Cystatin C, and GFR in Children and Young Adults With Pediatric Kidney Diseases: A Report From the Chronic Kidney Disease in Children (CKiD) Study

RATIONALE & OBJECTIVE

Recent reassessment of the use of race in estimated glomerular filtration rate (eGFR) in adults has instigated questions about the role of race in eGFR expressions for children. Little research has examined the associations of self-reported race with measured GFR (mGFR) adjusting for serum creatinine or cystatin C in children and young adults with chronic kidney disease (CKD). This study examined these associations and evaluated the performance of the previously published "U25" (under the age of 25 years) eGFR equations in a large cohort of children and young adults with CKD.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

Participants in the Chronic Kidney Disease in Children (CKiD) study including 190 Black and 675 non-Black participants contributing 473 and 1,897 annual person-visits, respectively.

EXPOSURE

Self- or parental-reported race (Black, non-Black). Adjustment for serum creatinine or cystatin C, body size, and socioeconomic status.

OUTCOME

mGFR based on iohexol clearance.

ANALYTICAL APPROACH

Linear regression with generalized estimating equations, stratified by age (<6, 6-12, 12-18, and ≥18 years) incorporating serum creatinine or serum cystatin C. Contrasting performance in different self-reported racial groups of the U25 eGFR equations.

RESULTS

Self-reported Black race was significantly associated with 12.8% higher mGFR among children in regression models including serum creatinine. Self-reported Black race was significantly associated with 3.5% lower mGFR after adjustment for cystatin C overall but was not significant for those over 12 years. The results were similar after adjustment for body size and socioeconomic factors. The average of creatinine- and cystatin C-based U25 equations was unbiased by self-reported race groups.

LIMITATIONS

Small number of children < 6 years; lean body mass was estimated.

CONCLUSIONS

Differences in the creatinine-mGFR relationship by self-reported race were observed in children and young adults with CKD and were consistent with findings in adults. Smaller and opposite differences were observed for the cystatin C-mGFR relationship, especially in the younger age group. We recommend inclusion of children for future investigations of biomarkers to estimate GFR. Importantly, for GFR estimation among those under 25 years of age, the average of the new U25 creatinine and cystatin C equations without race coefficients yields unbiased estimates of mGFR.

Low variability of plant protein intake in the CKiD cohort does not demonstrate changes in estimated GFR nor electrolyte balance

BACKGROUND

Vegetable or plant-based sources of protein may confer health benefits in children with progressive kidney disease. Our aims were to understand the effect of the proportion of vegetable protein intake on changes in estimated GFR and to understand the effect of the proportion of vegetable protein intake on serum levels of bicarbonate, phosphorus, and potassium.

METHODS

Children with baseline eGFR between 30 and 90 mL/min/1.73 m² were recruited from 59 centers across North America as part of the chronic kidney disease in children (CKiD) study. The percentage of dietary vegetable protein (VP%) was gathered from annual Food Frequency Questionnaires. We performed longitudinal linear mixed models to determine the effect of VP% on eGFR and longitudinal logistic mixed models to determine the effect of VP% on electrolyte balance (potassium, phosphorus, bicarbonate).

RESULTS

Two thousand visits from 631 subjects. Across all dichotomized groups of children (sex, African American race, Hispanic ethnicity, glomerular etiology of CKD, hypertension, anemia, hyperkalemia, hyperphosphatemia, acidosis, BMI < 95th percentile), the median VP% was 32-35%. The longitudinal mixed model analysis did not show any effect of VP% on eGFR electrolyte (bicarbonate, phosphorus, and potassium) abnormalities (p > 0.1).

CONCLUSIONS

A diverse cohort of children with CKD has a narrow and homogeneous intake of vegetable protein. Due to the low variability of plant-based protein in the cohort, there were no associations between the percentage of plant protein intake and changes in eGFR nor electrolyte balance. A higher resolution version of the Graphical abstract is available as Supplementary information.

Neurobehavioral morbidity of pediatric mild sleep-disordered breathing and obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea is associated with neurobehavioral dysfunction, but the relationship between disease severity as measured by the apnea-hypopnea index and neurobehavioral morbidity is unclear. The objective of our study is to compare the neurobehavioral morbidity of mild sleep-disordered breathing versus obstructive sleep apnea.

METHODS

Children 3-12 years old recruited for mild sleep-disordered breathing (snoring with obstructive apnea-hypopnea index < 3) into the Pediatric Adenotonsillectomy Trial for Snoring were compared to children 5-9 years old recruited for obstructive sleep apnea (obstructive apnea-hypopnea 2-30) into the Childhood Adenotonsillectomy Trial. Baseline demographic, polysomnographic, and neurobehavioral outcomes were compared using univariable and multivariable analysis.

RESULTS

The sample included 453 participants with obstructive sleep apnea (median obstructive apnea-hypopnea index 5.7) and 459 participants with mild sleep-disordered breathing (median obstructive apnea-hypopnea index 0.5). By polysomnography, participants with obstructive sleep apnea had poorer sleep efficiency and more arousals. Children with mild sleep-disordered breathing had more abnormal executive function scores (adjusted odds ratio 1.96, 95% CI 1.30-2.94) compared to children with obstructive sleep apnea. There were also elevated Conners scores for inattention (adjusted odds ratio 3.16, CI 1.98-5.02) and hyperactivity (adjusted odds ratio 2.82, CI 1.83-4.34) in children recruited for mild sleep-disordered breathing.

CONCLUSIONS

Abnormal executive function, inattention, and hyperactivity were more common in symptomatic children recruited into a trial for mild sleep-disordered breathing compared to children recruited into a trial for obstructive sleep apnea. Young, snoring children with only minimally elevated apnea-hypopnea levels may still be at risk for deficits in executive function and attention.

TRIAL REGISTRATION

Pediatric Adenotonsillectomy for Snoring (PATS), NCT02562040; Childhood Adenotonsillectomy Trial (CHAT), NCT00560859.

Health and Dental Insurance and Health Care Utilization Among Children, Adolescents, and Young Adults With CKD: Findings From the CKiD Cohort Study

Rationale & Objective

To understand the association between health and dental insurance status and health and dental care utilization, and their relationship with disease severity in a population with childhood-onset chronic kidney disease (CKD).

Study Design

Observational cohort study.

Settings & Participants

Nine hundred fifty-three participants contributing 4,369 person-visits (unit of analysis) in the United States enrolled in the Chronic Kidney Disease in Children (CKiD) Study from 2005 to 2019.

Exposures

Health insurance (private vs public vs none) and dental insurance (presence vs absence) self-reported at annual visits.

Outcomes

Self-reported suboptimal health care utilization in the past year, defined separately as not visiting a private physician, visiting the emergency room, visiting the emergency room at least twice, being hospitalized, and self-reported suboptimal dental care utilization over the past year, defined as not receiving dental care.

Analytical Approach

Repeated measures Poisson regression models were fit to estimate and compare utilization by insurance type and disease severity at the prior visit. Additional unadjusted and adjusted models were fit, as well as models including interactions between insurance and Black race, maternal education, and income.

Results

Those with public health insurance were more likely to report suboptimal health care utilization across the CKD severity spectrum, and lack of dental insurance was strongly associated with lack of dental care. These relationships varied depending on strata of socioeconomic status and race but the effect measure modification was not significant.

Limitations

Details of insurance coverage were unavailable; reasons for emergency care or type of private physician visited were unknown.

Conclusions

Pediatric nephrology programs may consider interventions to help direct supportive resources to families with public insurance who are at higher risk for suboptimal utilization of care. Insurance providers should identify areas to expand access for families of children with CKD.

Longitudinal Associations between Low Serum Bicarbonate and Linear Growth in Children with CKD

Background

Poor linear growth is a consequence of chronic kidney disease (CKD) that has been linked to adverse outcomes. Metabolic acidosis (MA) has been identified as a risk factor for growth failure. We investigated the longitudinal relationship between MA and linear growth in children with CKD and examined whether treatment of MA modified linear growth.

Methods

To describe longitudinal associations between MA and linear growth, we used serum bicarbonate levels, height measurements, and standard deviation (z scores) of children enrolled in the prospective cohort study Chronic Kidney Disease in Children. Analyses were adjusted for covariates recognized as correlating with poor growth, including demographic characteristics, glomerular filtration rate (GFR), proteinuria, calcium, phosphate, parathyroid hormone, and CKD duration. CKD diagnoses were analyzed by disease categories, nonglomerular or glomerular.

Results

The study population included 1082 children with CKD: 808 with nonglomerular etiologies and 274 with glomerular etiologies. Baseline serum bicarbonate levels ≤22 mEq/L were associated with worse height z scores in all children. Longitudinally, serum bicarbonate levels ≤18 and 19-22 mEq/L were associated with worse height z scores in children with nonglomerular CKD causes, with adjusted mean values of -0.39 (95% CI, -0.58 to -0.2) and -0.17 (95% CI, -0.28 to -0.05), respectively. Children with nonglomerular disease and more severe GFR impairment had a higher risk for worse height z score. A significant association was not found in children with glomerular diseases. We also investigated the potential effect of treatment of MA on height in children with a history of alkali therapy use, finding that only persistent users had a significant positive association between their height z score and higher serum bicarbonate levels.

Conclusions

We observed a longitudinal association between MA and lower height z score. Additionally, persistent alkali therapy use was associated with better height z scores. Future clinical trials of alkali therapy need to evaluate this relationship prospectively.

Overview of the findings and advances in the neurocognitive and psychosocial functioning of mild to moderate pediatric CKD: perspectives from the Chronic Kidney Disease in Children (CKiD) cohort study

The Chronic Kidney Disease in Children (CKiD) prospective cohort study was designed to address the neurocognitive, growth, cardiovascular, and disease progression of children and adolescents with mild to moderate CKD. The study has had continuous funding from NIDDK for 17 years and has contributed significant advances in pediatric CKD. The goals of this educational review are threefold: (1) to provide an overview of the neurocognitive and psychosocial studies from CKiD to date; (2) to provide best practice recommendations for those working with the neurocognitive and psychosocial aspects of pediatric CKD based on CKiD findings; and (3) to help chart future goals and directives for both research and clinical practice. This collection of 22 empirical studies has produced a number of key findings for children and adolescents with mild to moderate CKD. While various studies suggest a relatively positive presentation for this population as a whole, without evidence of significant impairment or deterioration, findings do indicate the presence of neurocognitive dysfunction, emotional-behavioral difficulties, and lower quality of life for many children with CKD. These findings support the promotion of best practices that are accompanied by additional future clinical and research initiatives with this patient population.

Using Machine Learning to Identify Metabolomic Signatures of Pediatric Chronic Kidney Disease Etiology

BACKGROUND

Untargeted plasma metabolomic profiling combined with machine learning (ML) may lead to discovery of metabolic profiles that inform our understanding of pediatric CKD causes. We sought to identify metabolomic signatures in pediatric CKD based on diagnosis: FSGS, obstructive uropathy (OU), aplasia/dysplasia/hypoplasia (A/D/H), and reflux nephropathy (RN).

METHODS

Untargeted metabolomic quantification (GC-MS/LC-MS, Metabolon) was performed on plasma from 702 Chronic Kidney Disease in Children study participants (n: FSGS=63, OU=122, A/D/H=109, and RN=86). Lasso regression was used for feature selection, adjusting for clinical covariates. Four methods were then applied to stratify significance: logistic regression, support vector machine, random forest, and extreme gradient boosting. ML training was performed on 80% total cohort subsets and validated on 20% holdout subsets. Important features were selected based on being significant in at least two of the four modeling approaches. We additionally performed pathway enrichment analysis to identify metabolic subpathways associated with CKD cause.

RESULTS

ML models were evaluated on holdout subsets with receiver-operator and precision-recall area-under-the-curve, F1 score, and Matthews correlation coefficient. ML models outperformed no-skill prediction. Metabolomic profiles were identified based on cause. FSGS was associated with the sphingomyelin-ceramide axis. FSGS was also associated with individual plasmalogen metabolites and the subpathway. OU was associated with gut microbiome-derived histidine metabolites.

CONCLUSION

ML models identified metabolomic signatures based on CKD cause. Using ML techniques in conjunction with traditional biostatistics, we demonstrated that sphingomyelin-ceramide and plasmalogen dysmetabolism are associated with FSGS and that gut microbiome-derived histidine metabolites are associated with OU.

The Similarities and Differences Between Glomerular vs. Non-glomerular Diagnoses on Intelligence and Executive Functions in Pediatric Chronic Kidney Disease: A Brief Report

Pediatric chronic kidney disease (CKD) appears to be a heterogeneous group of conditions, but this heterogeneity has not been explored with respect to its impact on neurocognitive functioning. This study investigated the neurocognitive functioning of those with glomerular (G) vs. non-glomerular (NG) diagnoses. Data from the North American CKiD Study were employed and the current study included 1,003 children and adolescents with mild to moderate CKD. The G Group included 260 participants (median age = 14.7 years) and the NG Group included 743 individuals (median age = 9.0 years). Neurocognitive measures assessed IQ, inhibitory control, attention regulation, problem solving, working memory, and overall executive functioning. Data from all visits were included in the linear mixed model analyses. After adjusting for sociodemographic and CKD-related covariates, results indicated no differences between the diagnostic groups on measures of IQ, problem solving, working memory, and attention regulation. There was a trend for the G group to receive better parent ratings on their overall executive functions (p < 0.07), with a small effect size being present. Additionally, there was a significant G group X hypertension interaction (p < 0.003) for inhibitory control, indicating that those with both a G diagnosis and hypertension performed more poorly than the NG group with hypertension. These findings suggest that the separation of G vs. NG CKD produced minimal, but specific group differences were observed. Ongoing examination of the heterogeneity of pediatric CKD on neurocognition, perhaps at a different time point in disease progression or using a different model, appears warranted.

Nocturnal Dipping and Left Ventricular Mass Index in the Chronic Kidney Disease in Children Cohort

BACKGROUND AND OBJECTIVES

The physiologic nocturnal BP decline is often blunted in patients with CKD; however, the consequences of BP nondipping in children are largely unknown. Our objective was to determine risk factors for nondipping and to investigate if nondipping is associated with higher left ventricular mass index in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a cross-sectional analysis of ambulatory BP monitoring and echocardiographic data in participants of the Chronic Kidney Disease in Children study. Multivariable linear and spline regression analyses were used to evaluate the relationship of risk factors with dipping and of dipping with left ventricular mass index.

RESULTS

Within 552 participants, mean age was 11 (±4) years, mean eGFR was 53 (±20) ml/min per 1.73 m², and 41% were classified as nondippers. In participants with nonglomerular CKD, female sex and higher sodium intake were significantly associated with less systolic and diastolic dipping (P≤0.05). In those with glomerular CKD, Black race and greater proteinuria were significantly associated with less systolic and diastolic dipping (P≤0.05). Systolic dipping and diastolic dipping were not significantly associated with left ventricular mass index; however, in spline regression plots, diastolic dipping appeared to have a nonlinear relationship with left ventricular mass index. As compared with diastolic dipping of 20%-25%, dipping of <20% was associated with 1.41-g/m^2.7-higher left ventricular mass index (95% confidence interval, -0.47 to 3.29), and dipping of >25% was associated with 1.98-g/m^2.7-higher left ventricular mass index (95% confidence interval, -0.77 to 4.73), although these relationships did not achieve statistical significance.

CONCLUSIONS

Black race, female sex, and greater proteinuria and sodium intake were significantly associated with blunted dipping in children with CKD. We did not find a statistically significant association between dipping and left ventricular mass index.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_12_20_CJN09810721.mp3.

Using a Multi-Institutional Pediatric Learning Health System to Identify Systemic Lupus Erythematosus and Lupus Nephritis: Development and Validation of Computable Phenotypes

BACKGROUND AND OBJECTIVES

Performing adequately powered clinical trials in pediatric diseases, such as SLE, is challenging. Improved recruitment strategies are needed for identifying patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Electronic health record algorithms were developed and tested to identify children with SLE both with and without lupus nephritis. We used single-center electronic health record data to develop computable phenotypes composed of diagnosis, medication, procedure, and utilization codes. These were evaluated iteratively against a manually assembled database of patients with SLE. The highest-performing phenotypes were then evaluated across institutions in PEDSnet, a national health care systems network of >6.7 million children. Reviewers blinded to case status used standardized forms to review random samples of cases (n=350) and noncases (n=350).

RESULTS

Final algorithms consisted of both utilization and diagnostic criteria. For both, utilization criteria included two or more in-person visits with nephrology or rheumatology and ≥60 days follow-up. SLE diagnostic criteria included absence of neonatal lupus, one or more hydroxychloroquine exposures, and either three or more qualifying diagnosis codes separated by ≥30 days or one or more diagnosis codes and one or more kidney biopsy procedure codes. Sensitivity was 100% (95% confidence interval [95% CI], 99 to 100), specificity was 92% (95% CI, 88 to 94), positive predictive value was 91% (95% CI, 87 to 94), and negative predictive value was 100% (95% CI, 99 to 100). Lupus nephritis diagnostic criteria included either three or more qualifying lupus nephritis diagnosis codes (or SLE codes on the same day as glomerular/kidney codes) separated by ≥30 days or one or more SLE diagnosis codes and one or more kidney biopsy procedure codes. Sensitivity was 90% (95% CI, 85 to 94), specificity was 93% (95% CI, 89 to 97), positive predictive value was 94% (95% CI, 89 to 97), and negative predictive value was 90% (95% CI, 84 to 94). Algorithms identified 1508 children with SLE at PEDSnet institutions (537 with lupus nephritis), 809 of whom were seen in the past 12 months.

CONCLUSIONS

Electronic health record-based algorithms for SLE and lupus nephritis demonstrated excellent classification accuracy across PEDSnet institutions.

Decreased Neural Connectivity in the Default Mode Network Among Youth and Young Adults With Chronic Kidney Disease

An increasing amount of literature has indicated that chronic kidney disease (CKD) is associated with cognitive deficits that increase with worsening disease severity. Although abnormalities in brain structure have been widely documented, few studies to date have examined the functioning of brain areas associated with the specific cognitive domains affected by CKD (namely, attention and executive functions). Furthermore, few studies have examined functional connectivity among CKD youth who are relatively early in the course of the disease. The present study used functional magnetic resonance imaging to examine the resting state connectivity in 67 youth with CKD (mean age, 17 y) and 58 age-matched healthy controls. Using seed-based multiple regression, decreased connectivity was observed within the anterior cingulate portion of the default mode network. In addition, decreased connectivity within the dorsolateral prefrontal cortex, paracingulate gyrus, and frontal pole were correlated significantly with disease severity. These data indicate that connectivity deficits in circuits implementing attentional processes may represent an early marker for cognitive decline in CKD.