Longitudinal plasma metabolome patterns and relation to kidney function and proteinuria in pediatric chronic kidney disease.

INTRODUCTION: Understanding plasma metabolome patterns in relation to changing kidney function in pediatric chronic kidney disease (CKD) is important for continued research for identifying novel biomarkers, characterizing biochemical pathophysiology, and developing targeted interventions. There is a limited number of studies of longitudinal metabolomics, and virtually none in pediatric CKD. METHODS: The Chronic Kidney Disease in Children (CKiD) study is a multi-institutional, prospective cohort that enrolled children aged six-months to 16-years with estimated glomerular filtration rate (eGFR) 30-90ml/min/1.73m2. Untargeted metabolomics profiling was performed on plasma samples from the baseline, two-, and four-year study visits. There were technologic updates in the metabolomic profiling platform used between the baseline and follow-up assays. Statistical approaches were adopted to avoid direct comparison of baseline and follow-up measurements.To identify metabolite associations with eGFR or urine protein:creatinine (UPCR) among all three timepoints, we applied linear mixed effects (LME) models. To identify metabolites associated with time, we applied LME models to the two- and four-year follow-up data. We applied linear regression analysis to examine associations between change in metabolite level over time (∆level) and change in eGFR (∆eGFR) and UPCR (∆UPCR). We reported significance based on both the False Discovery Rate (FDR) <0.05 and p<0.05. RESULTS: There were 1156 person-visits (N: baseline=626, 2-year=254, 4-year=276) included. There were 622 metabolites with standardized measurements at all three timepoints. In LME modeling, 406 and 343 metabolites associated with eGFR and UPCR at FDR<0.05 respectively. Among 530 follow-up person-visits, 158 metabolites showed differences over time at FDR<0.05. For participants with complete data at both follow-up visits (N=123), we report 35 metabolites with ∆level∼∆eGFR associations significant at FDR<0.05. There were no metabolites with significant ∆level∼∆UPCR associations at FDR<0.05. We report 16 metabolites with ∆level∼∆UPCR associations at p<0.05 and associations with UPCR in LME modeling at FDR<0.05. CONCLUSION: We characterized longitudinal plasma metabolomic patterns associated with eGFR and UPCR in a large pediatric CKD population. Many of these metabolite signals have been associated with CKD progression, etiology, and proteinuria in previous CKD Biomarkers Consortium studies. There were also novel metabolite associations with eGFR and proteinuria detected.

Psychotropic Medication Usage in Pediatric CKD: Reporting from the Chronic Kidney Disease in Children Cohort.

BACKGROUND: Mental health disorders (MHD) within the pediatric chronic kidney disease (CKD) population are prevalent. The frequency is unknown with which psychotropic medications that commonly treat these conditions are used in this population. METHODS: Data from the Chronic Kidney Disease in Children (CKiD) cohort study were utilized to describe the use of psychotropic medications and patient-related characteristics of use. Medications were classified into 3 groups: antidepressants, CNS stimulants, and antipsychotic/mood stabilizing medications. Participant age, sex, CKD severity, and duration of medication use were ascertained. Medication use was evaluated in parallel with CKD disease type, presence of urological comorbidity, and hypertension. Chi-square tests compared subgroup medication use. RESULTS: Among 1074 CKiD participants (median baseline age 9.8 years), 6% (n=60) of participants used psychotropic medications at study entry with 11% reporting incident use of any medication category (n=120). CNS stimulants were most common at baseline. Antidepressants were more frequent among incident users at 7%. Use of two or more medications was rare (3%). Median eGFR at medication initiation was 45 ml/min|1.73m2. CNS stimulants were reported at a higher rate in males compared to females (p<0.05). CONCLUSIONS: 11% of CKiD patients report incident use of any psychotropic medication, with 7% reporting incident use of antidepressants. Future work is warranted to better ascertain the frequency, safety, and efficacy of psychotropic medication usage in relationship to formal MHD diagnoses in the pediatric CKD population.

A Drosophila model to screen Alport syndrome COL4A5 variants for their functional pathogenicity.

Alport syndrome is a hereditary chronic kidney disease, attributed to rare pathogenic variants in either of three collagen genes (COL4A3/4/5) with most localized in COL4A5. Trimeric type IV Collagen α3α4α5 is essential for the glomerular basement membrane that forms the kidney filtration barrier. A means to functionally assess the many candidate variants and determine pathogenicity is urgently needed. We used Drosophila, an established model for kidney disease, and identify Col4a1 as the functional homolog of human COL4A5 in the fly nephrocyte (equivalent of human podocyte). Fly nephrocytes deficient for Col4a1 showed an irregular and thickened basement membrane and significantly reduced nephrocyte filtration function. This phenotype was restored by expressing human reference (wildtype) COL4A5, but not by COL4A5 carrying any of three established pathogenic patient-derived variants. We then screened seven additional patient COL4A5 variants; their ClinVar classification was either likely pathogenic or of uncertain significance. The findings support pathogenicity for four of these variants; the three others were found benign. Thus, demonstrating the effectiveness of this Drosophila in vivo kidney platform in providing the urgently needed variant-level functional validation.

Plasma Metabolomics of Dietary Intake of Protein-Rich Foods and Kidney Disease Progression in Children.

OBJECTIVE: Evidence regarding the efficacy of a low-protein diet for patients with CKD is inconsistent and recommending a low-protein diet for pediatric patients is controversial. There is also a lack of objective biomarkers of dietary intake. The purpose of this study was to identify plasma metabolites associated with dietary intake of protein and to assess whether protein-related metabolites are associated with CKD progression. METHODS: Nontargeted metabolomics was conducted in plasma samples from 484 Chronic Kidney Disease in Children (CKiD) participants. Multivariable linear regression estimated the cross-sectional association between 949 known, nondrug metabolites and dietary intake of total protein, animal protein, plant protein, chicken, dairy, nuts and beans, red and processed meat, fish, and eggs, adjusting for demographic, clinical, and dietary covariates. Cox proportional hazards models assessed the prospective association between protein-related metabolites and CKD progression defined as the initiation of kidney replacement therapy or 50% eGFR reduction, adjusting for demographic and clinical covariates. RESULTS: One hundred and twenty-seven (26%) children experienced CKD progression during 5 years of follow-up. Sixty metabolites were significantly associated with dietary protein intake. Among the 60 metabolites, 10 metabolites were significantly associated with CKD progression (animal protein: n = 1, dairy: n = 7, red and processed meat: n = 2, nuts and beans: n = 1), including one amino acid, one cofactor and vitamin, 4 lipids, 2 nucleotides, one peptide, and one xenobiotic. 1-(1-enyl-palmitoyl)-2-oleoyl-glycerophosphoethanolamine (GPE, P-16:0/18:1) was positively associated with dietary intake of red and processed meat, and a doubling of its abundance was associated with 88% higher risk of CKD progression. 3-ureidopropionate was inversely associated with dietary intake of red and processed meat, and a doubling of its abundance was associated with 48% lower risk of CKD progression. CONCLUSIONS: Untargeted plasma metabolomic profiling revealed metabolites associated with dietary intake of protein and CKD progression in a pediatric population.

Associations between anemia and FGF23 in the CKiD study.

BACKGROUND: Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that plays a central role in chronic kidney disease-mineral bone disorder and is associated with CKD progression and cardiovascular morbidity. Factors related to CKD-associated anemia, including iron deficiency, can increase FGF23 production. This study aimed to assess whether anemia and/or iron deficiency are associated with increased circulating concentrations of FGF23 in the large, well-characterized Chronic Kidney Disease in Children (CKiD) study cohort. METHODS: Hemoglobin concentrations, iron parameters, C-terminal (total) FGF23, intact FGF23, and relevant covariables were measured in cross-sectional analysis of CKiD study subjects. RESULTS: In 493 pediatric patients with CKD (median [interquartile range] age 13 [9, 16] years), the median estimated glomerular filtration rate was 48 [35, 61] ml/min/1.73 m2, and 103 patients (21%) were anemic. Anemic subjects had higher total FGF23 concentrations than non-anemic subjects (204 [124, 390] vs. 109 [77, 168] RU/ml, p < 0.001). In multivariable linear regression modeling, anemia was independently associated with higher total FGF23, after adjustment for demographic, kidney-related, mineral metabolism, and inflammatory covariables (standardized ß (95% confidence interval) 0.10 (0.04, 0.17), p = 0.002). In the subset of subjects with available iron parameters (n = 191), iron deficiency was not associated with significantly higher total FGF23 concentrations. In the subgroup that had measurements of both total and intact FGF23 (n = 185), in fully adjusted models, anemia was significantly associated with higher total FGF23 (standardized ß (95% CI) 0.16 (0.04, 0.27), p = 0.008) but not intact FGF23 (standardized ß (95% CI) 0.02 (-0.12, 0.15), p = 0.81). CONCLUSIONS: In this cohort of pediatric patients with CKD, anemia was associated with increased total FGF23 levels but was not independently associated with elevated intact FGF23, suggesting possible effects on both FGF23 production and cleavage. Further studies are warranted to investigate non-mineral factors affecting FGF23 production and metabolism in CKD.

Evaluation of novel candidate filtration markers from a global metabolomic discovery for glomerular filtration rate estimation.

Creatinine and cystatin-C are recommended for estimating glomerular filtration rate (eGFR) but accuracy is suboptimal. Here, using untargeted metabolomics data, we sought to identify candidate filtration markers for a new targeted assay using a novel approach based on their maximal joint association with measured GFR (mGFR) and with flexibility to consider their biological properties. We analyzed metabolites measured in seven diverse studies encompasing 2,851 participants on the Metabolon H4 platform that had Pearson correlations with log mGFR and used a stepwise approach to develop models to < -0.5 estimate mGFR with and without inclusion of creatinine that enabled selection of candidate markers. In total, 456 identified metabolites were present in all studies, and 36 had correlations with mGFR < -0.5. A total of 2,225 models were developed that included these metabolites; all with lower root mean square errors and smaller coefficients for demographic variables compared to estimates using untargeted creatinine. Seventeen metabolites were chosen, including 12 new candidate filtration markers. The selected metabolites had strong associations with mGFR and little dependence on demographic factors. Candidate metabolites were identified with maximal joint association with mGFR and minimal dependence on demographic variables across many varied clinical settings. These metabolites are excreted in urine and represent diverse metabolic pathways and tubular handling. Thus, our data can be used to select metabolites for a multi-analyte eGFR determination assay using mass spectrometry that potentially offers better accuracy and is less prone to non-GFR determinants than the current eGFR biomarkers.

Pubertal luteinizing hormone levels in children with chronic kidney disease and association with change in glomerular filtration rate.

BACKGROUND: Children with chronic kidney disease (CKD) are at risk for abnormalities in pubertal development. We aimed to describe the timing of pubertal onset by luteinizing hormone (LH) levels and the association between hormonal onset of puberty with changes in GFR. METHODS: Data from the Chronic Kidney Disease in Children (CKiD) study were collected prospectively. GFR was estimated at annual visits and measured by iohexol clearance every other year. LH was measured from stored repository serum samples in a nested sample of 124 participants. Hormonal onset of puberty was defined as LH level greater than or equal to 0.3 IU/L. A mixed effects model with random intercepts and slopes was used to compare the slope of decline of GFR before and after hormonal onset of puberty. The model was adjusted for age, glomerular disease diagnosis, baseline proteinuria on the log scale, and BMI. RESULTS: Median age at hormonal onset of puberty was 9.9 years (IQR 8.1, 11.9) in girls and 10.2 years (IQR 9.2, 11.0) in boys. The mixed effects model showed faster decline in both estimated GFR and measured GFR in boys after hormonal onset of puberty (p < 0.001), and a similar but attenuated accelerated estimated GFR decline was observed for girls with no difference for measured GFR. CONCLUSIONS: LH levels in the post-pubertal range were observed prior to clinical manifestations of puberty in children with CKD. Hormonal onset of puberty was associated with faster decline in GFR, particularly among boys with CKD.

Antihypertensive medication nonadherence and target organ damage in children with chronic kidney disease.

BACKGROUND: Nonadherence is common in children with chronic kidney disease (CKD). This may contribute to inadequate blood pressure control and adverse outcomes. This study examined associations between antihypertensive medication nonadherence, ambulatory blood pressure monitoring (ABPM) parameters, kidney function, and cardiac structure among children with CKD. METHODS: We performed secondary analyses of data from the CKD in Children (CKiD) study, including participants with treated hypertension who underwent ABPM, laboratory testing, and echocardiography biannually. Nonadherence was defined by self-report of any missed antihypertensive medication 7 days prior to the study visit. Linear regression and mixed-effects models were used to assess the association of nonadherence with baseline and time-updated ABPM profiles, estimated glomerular filtration rate (eGFR), urine protein to creatinine ratio (UPCR), and left ventricular mass index (LVMI). RESULTS: Five-hundred and eight participants met inclusion criteria, followed for a median of 2.9 years; 212 (42%) were female, with median age 13 years (IQR 10-16), median baseline eGFR 49 (33-64) ml/min/1.73 m2 and median UPCR 0.4 (0.1-1.0) g/g. Nonadherence occurred in 71 (14%) participants. Baseline nonadherence was not significantly associated with baseline 24-h ABPM parameters (for example, mean 24-h SBP [ß - 0.1, 95% CI - 2.7, 2.5]), eGFR (ß 1.0, 95% CI - 0.9, 1.2), UCPR (ß 1.1, 95% CI - 0.8, 1.5), or LVMI (ß 0.6, 95% CI - 1.6, 2.9). Similarly, there were no associations between baseline nonadherence and time-updated outcome measures. CONCLUSIONS: Self-reported antihypertensive medication nonadherence occurred in 1 in 7 children with CKD. We found no associations between nonadherence and kidney function or cardiac structure over time. A higher resolution version of the Graphical abstract is available as Supplementary information.

Regional Variation in Hemoglobin Distribution Among Individuals With CKD: the ISN International Network of CKD Cohorts.

Introduction: Despite recognized geographic and sex-based differences in hemoglobin in the general population, these factors are typically ignored in patients with chronic kidney disease (CKD) in whom a single therapeutic range for hemoglobin is recommended. We sought to compare the distribution of hemoglobin across international nondialysis CKD populations and evaluate predictors of hemoglobin. Methods: In this cross-sectional study, hemoglobin distribution was evaluated in each cohort overall and stratified by sex and estimated glomerular filtration rate (eGFR). Relationships between candidate predictors and hemoglobin were assessed from linear regression models in each cohort. Estimates were subsequently pooled in a random effects model. Results: A total of 58,613 participants from 21 adult cohorts (median eGFR range of 17-49 ml/min) and 3 pediatric cohorts (median eGFR range of 26-45 ml/min) were included with broad geographic representation. Hemoglobin values varied substantially among the cohorts, overall and within eGFR categories, with particularly low mean hemoglobin observed in women from Asian and African cohorts. Across the eGFR range, women had a lower hemoglobin compared to men, even at an eGFR of 15 ml/min (mean difference 5.3 g/l, 95% confidence interval [CI] 3.7-6.9). Lower eGFR, female sex, older age, lower body mass index, and diabetic kidney disease were all independent predictors of a lower hemoglobin value; however, this only explained a minority of variance (R2 7%-44% across cohorts). Conclusion: There are substantial regional differences in hemoglobin distribution among individuals with CKD, and the majority of variance is unexplained by demographics, eGFR, or comorbidities. These findings call for a renewed interest in improving our understanding of hemoglobin determinants in specific CKD populations.

Circulating Metabolomic Associations with Neurocognitive Outcomes in Pediatric CKD.

BACKGROUND: Children with CKD are at risk for impaired neurocognitive functioning. We investigated metabolomic associations with neurocognition in children with CKD. METHODS: We leveraged data from the Chronic Kidney Disease in Children (CKiD) study and the Neurocognitive Assessment and Magnetic Resonance Imaging Analysis of Children and Young Adults with Chronic Kidney Disease (NiCK) study. CKiD is a multi-institutional cohort that enrolled children aged 6 months to 16 years with eGFR 30-90 ml/min per 1.73 m 2 ( n =569). NiCK is a single-center cross-sectional study of participants aged 8-25 years with eGFR<90 ml/min per 1.73 m 2 ( n =60) and matched healthy controls ( n =67). Untargeted metabolomic quantification was performed on plasma (CKiD, 622 metabolites) and serum (NiCK, 825 metabolites) samples. Four neurocognitive domains were assessed: intelligence, attention regulation, working memory, and parent ratings of executive function. Repeat assessments were performed in CKiD at 2-year intervals. Linear regression and linear mixed-effects regression analyses adjusting for age, sex, delivery history, hypertension, proteinuria, CKD duration, and glomerular versus nonglomerular diagnosis were used to identify metabolites associated with neurocognitive z-scores. Analyses were performed with and without adjustment for eGFR. RESULTS: There were multiple metabolite associations with neurocognition observed in at least two of the analytic samples (CKiD baseline, CKiD follow-up, and NiCK CKD). Most of these metabolites were significantly elevated in children with CKD compared with healthy controls in NiCK. Notable signals included associations with parental ratings of executive function: phenylacetylglutamine, indoleacetylglutamine, and trimethylamine N-oxide-and with intelligence: γ -glutamyl amino acids and aconitate. CONCLUSIONS: Several metabolites were associated with neurocognitive dysfunction in pediatric CKD, implicating gut microbiome-derived substances, mitochondrial dysfunction, and altered energy metabolism, circulating toxins, and redox homeostasis.

Association Between Dialysis Facility Ownership and Mortality Risk in Children With Kidney Failure.

Importance: In adults, treatment at profit dialysis facilities has been associated with a higher risk of death. Objective: To determine whether profit status of dialysis facilities is associated with the risk of death in children with kidney failure treated with dialysis and whether any such association is mediated by differences in access to transplant. Design, Setting, and Participants: This retrospective cohort study reviewed US Renal Data System records of 15 359 children who began receiving dialysis for kidney failure between January 1, 2000, and December 31, 2019, in US dialysis facilities. The data analysis was performed between May 2, 2022, and June 15, 2023. Exposure: Time-updated profit status of dialysis facilities. Main Outcomes and Measures: Adjusted Fine-Gray models were used to determine the association of time-updated profit status of dialysis facilities with risk of death, treating kidney transplant as a competing risk. Cox proportional hazards regression models were also used to determine time-updated profit status with risk of death regardless of transplant status. Results: The final cohort included 8465 boys (55.3%) and 6832 girls (44.7%) (median [IQR] age, 12 [3-15] years). During a median follow-up of 1.4 (IQR, 0.6-2.7) years, with censoring at transplant, the incidence of death was higher at profit vs nonprofit facilities (7.03 vs 4.06 per 100 person-years, respectively). Children treated at profit facilities had a 2.07-fold (95% CI, 1.83-2.35) higher risk of death compared with children at nonprofit facilities in adjusted analyses accounting for the competing risk of transplant. When follow-up was extended regardless of transplant status, the risk of death remained higher for children treated in profit facilities (hazard ratio, 1.47; 95% CI, 1.35-1.61). Lower access to transplant in profit facilities mediated 67% of the association between facility profit status and risk of death (95% CI, 45%-100%). Conclusions and Relevance: Given the higher risk of death associated with profit dialysis facilities that is partially mediated by lower access to transplant, the study's findings indicate a need to identify root causes and targeted interventions that can improve mortality outcomes for children treated in these facilities.

Application of GFR estimating equations to children with normal, near-normal, or discordant GFR.

BACKGROUND: The objective was to determine the extent that eGFR formulas correspond to measured plasma iohexol clearance (iGFR) in children with normal or near normal kidney function, particularly how different eGFR formulas yield discordant results. METHODS: iGFR from 2 (iGFR-2pt) and 4 (iGFR-4pt) time points along with creatinine and/or cystatin C-based eGFR were measured in children with mild CKD, stages 1-2. eGFR was calculated using 6 equations: 3 under 25 (U25) formulas from the Chronic Kidney Disease in Children (CKiD) study, the full age-combined cystatin C (cysC) and creatinine spectrum (FAS-combined), the European Kidney Function Consortium (EKFC-creatinine) equation, and the Chronic Kidney Disease Epidemiology Collaboration (CKD-epi) cysC-based equation. RESULTS: Twenty-nine children were included, of which 22 had discordant creatinine vs. cystatin C-based eGFR by ≥ 15mL/min/1.73 m2. Overall, the FAS-combined had the least bias, while the U25 most accurately identified children with an eGFR < 90 mL/min/1.73 m2. When Cr-eGFR was ≥ 15 mL/min higher than CysC-eGFR, the U25 creatinine eGFR was closest to iGFR-4pt. When CysC eGFR was higher, the U25-combined was closest to iGFR-4pt. CONCLUSION: The formulas that most closely approximated the measured GFR varied depending on the pattern of discordant eGFR results. Based on the results, we recommend using the CKiD U25-combined formula to screen for children with a low GFR. Either the CKiD U25-combined or FAS-combined would be recommended for changes in eGFR longitudinally. However, because all formulas were discordant from the iGFR-4pt in over a third of participants, further refinement of pediatric eGFR formulas is needed at the normal/near-normal range. A higher resolution version of the Graphical abstract is available as Supplementary information.

Associations between collagen X biomarker and linear growth velocity in a pediatric chronic kidney disease cohort.

BACKGROUND: Collagen X biomarker (CXM) is a novel biomarker of linear growth velocity. We investigated whether CXM correlated with measured growth velocity in children with impaired kidney function. METHODS: We used data from children aged 2 through 16 years old enrolled in the Chronic Kidney Disease in Children (CKiD) study. We assessed the association between CXM level and growth velocity based on height measurements obtained at study visits using linear regression models constructed separately by sex, with and without adjustment for CKD covariates. Linear mixed-effects models were used to capture the between-individual and within-individual CXM changes over time associated with concomitant changes in growth velocity from baseline through follow-up. RESULTS: A total of 967 serum samples from 209 participants were assayed for CXM. CXM correlated more strongly in females compared to male participants. After adjustment for growth velocity and CKD covariates, only proteinuria in male participants affected CXM levels. Finally, we quantified the between- and within-participant associations between CXM level and growth velocity. A between-participant increase of 24% and 15% in CXM level in females and males, respectively, correlated with a 1 cm/year higher growth velocity. Within an individual participant, on average, 28% and 13% increases in CXM values in females and males, respectively, correlated with a 1 cm/year change in measured growth. CONCLUSIONS: CXM measurement is potentially a valuable aid for monitoring growth in pediatric CKD. However, future research, including studies of CXM metabolism, is needed to clarify whether CXM can be a surrogate of growth in children with CKD. A higher resolution version of the Graphical abstract is available as Supplementary information.

Clinical course and management of children with IgA vasculitis with nephritis.

BACKGROUND: IgA vasculitis is the most common vasculitis in children and is often complicated by acute nephritis (IgAVN). Risk of chronic kidney disease (CKD) among children with IgAVN remains unknown. This study aimed to describe the clinical management and kidney outcomes in a large cohort of children with IgAVN. METHODS: This observational cohort study used the PEDSnet database to identify children diagnosed with IgAV between January 1, 2009, and February 29, 2020. Demographic and clinical characteristics were compared among children with and without kidney involvement. For children followed by nephrology, clinical course, and management patterns were described. Patients were divided into four categories based on treatment: observation, renin-angiotensin-aldosterone system (RAAS) blockade, corticosteroids, and other immunosuppression, and outcomes were compared among these groups. RESULTS: A total of 6802 children had a diagnosis of IgAV, of whom 1139 (16.7%) were followed by nephrology for at least 2 visits over a median follow-up period of 1.7 years [0.4,4.2]. Conservative management was the most predominant practice pattern, consisting of observation in 57% and RAAS blockade in 6%. Steroid monotherapy was used in 29% and other immunosuppression regimens in 8%. Children receiving immunosuppression had higher rates of proteinuria and hypertension compared to those managed with observation (p < 0.001). At the end of follow-up, 2.6 and 0.5% developed CKD and kidney failure, respectively. CONCLUSIONS: Kidney outcomes over a limited follow-up period were favorable in a large cohort of children with IgAV. Immunosuppressive medications were used in those with more severe presentations and may have contributed to improved outcomes. A higher resolution version of the Graphical abstract is available as Supplementary information.

Development of an adaptive clinical web-based prediction tool for kidney replacement therapy in children with chronic kidney disease.

Clinicians need improved prediction models to estimate time to kidney replacement therapy (KRT) for children with chronic kidney disease (CKD). Here, we aimed to develop and validate a prediction tool based on common clinical variables for time to KRT in children using statistical learning methods and design a corresponding online calculator for clinical use. Among 890 children with CKD in the Chronic Kidney Disease in Children (CKiD) study, 172 variables related to sociodemographics, kidney/cardiovascular health, and therapy use, including longitudinal changes over one year were evaluated as candidate predictors in a random survival forest for time to KRT. An elementary model was specified with diagnosis, estimated glomerular filtration rate and proteinuria as predictors and then random survival forest identified nine additional candidate predictors for further evaluation. Best subset selection using these nine additional candidate predictors yielded an enriched model additionally based on blood pressure, change in estimated glomerular filtration rate over one year, anemia, albumin, chloride and bicarbonate. Four additional partially enriched models were constructed for clinical situations with incomplete data. Models performed well in cross-validation, and the elementary model was then externally validated using data from a European pediatric CKD cohort. A corresponding user-friendly online tool was developed for clinicians. Thus, our clinical prediction tool for time to KRT in children was developed in a large, representative pediatric CKD cohort with an exhaustive evaluation of potential predictors and supervised statistical learning methods. While our models performed well internally and externally, further external validation of enriched models is needed.

Trajectories of eGFR after kidney transplantation according to trajectories of eGFR prior to kidney replacement therapies in children with chronic kidney disease.

BACKGROUND: In children with chronic kidney disease (CKD), certain risk factors are associated with faster eGFR decline and earlier kidney failure. Whether these factors have lingering effects on post-transplant eGFR trajectory remains unclear. We characterized pre- and post-transplant eGFR trajectories in pediatric kidney transplant recipients by their pre-kidney replacement therapy (KRT) risk factors. METHODS: We studied eGFR trajectories before KRT initiation and after transplantation among Chronic Kidney Disease in Children (CKiD) Study participants. We used mixed-effects models to compare pre-KRT versus post-transplant eGFR trajectories within individual participants by 7 pre-KRT risk factors: glomerular/non-glomerular etiology, race, preemptive transplant, proteinuria, albuminuria, and systolic/diastolic blood pressure (SBP/DBP). RESULTS: We analyzed 1602 pre-KRT and 592 post-transplant eGFR measurements from 246 transplant recipients. Mean annual eGFR decline was decreased from 18.0% pre-KRT (95%CI, 16.1-19.8) to 5.0% post-transplant (95%CI, 3.3-6.7). All 7 pre-KRT risk factors showed strong associations with faster pre-KRT eGFR decline, but not with post-transplant eGFR decline; only albuminuria, high SBP, and high DBP reached statistical significance with notably attenuated associations. In our multivariable model of the pre-KRT risk factors, post-transplant eGFR decline was more rapid only when albuminuria and high SBP were both present. CONCLUSIONS: eGFR decline substantially slows down after transplant even among children with rapidly progressing forms of CKD. Nonetheless, those who had albuminuria and high SBP before KRT might continue to show faster eGFR decline after transplant, specifically when both risk factors were present. This subgroup might benefit from intensive pre-transplant management for at least one of the two risk factors. A higher resolution version of the Graphical abstract is available as Supplementary information.

Effect of Age on Hypertension Recognition in Children With Chronic Kidney Disease: A Report From the Chronic Kidney Disease in Children Study.

BACKGROUND: Young age has been associated with poorer control of hypertension in children with chronic kidney disease (CKD). Using data from the CKiD Study (Chronic Kidney Disease in Children), we examined the relationship between age, hypertensive blood pressure (BP) recognition, and pharmacologic BP control in children with nondialysis-dependent CKD. METHODS: Participants included 902 CKiD Study participants with CKD stages 2 to 4. A total of 3550 annual study visits met inclusion criteria and participants were stratified by age (0 to <7, ≥7 to <13, ≥13 to ≤18 years). Generalized estimating equations to account for repeated measures were applied to logistic regression analyses to evaluate the association of age with unrecognized hypertensive BP and medication use. RESULTS: Children <7 years of age had a higher prevalence of hypertensive BP and a lower prevalence of antihypertensive medication use compared with older children. At visits where participants <7 years of age had hypertensive BP readings, 46% had unrecognized, untreated hypertensive BP compared with 21% of visits for children ≥13 years of age. The youngest age group was associated with higher odds of unrecognized hypertensive BP (adjusted odds ratio, 2.11 [95% CI, 1.37-3.24]) and lower odds of antihypertensive medication use among those with unrecognized hypertensive BP (adjusted OR, 0.51 [95% CI, 0.27-0.996]). CONCLUSIONS: Children younger than 7 years of age with CKD are more likely to have both undiagnosed and undertreated hypertensive BP. Efforts to improve BP control in young children with CKD are needed to minimize development of cardiovascular disease and slow CKD progression.