Reduced kidney function and hypertension in adolescents with low birth weight, NHANES 1999-2016.

BACKGROUND: Chronic kidney disease (CKD) is a major health problem, and the risk of CKD and hypertension in children born low birth weight (LBW) is under-recognized. We hypothesized that children born with LBW would have a higher prevalence of reduced kidney function and hypertension. METHODS: Using the National Health and Nutrition Examination Survey (NHANES), we conducted a cross-sectional study to evaluate whether LBW (< 2500 g), very low birth weight (VLBW < 1500 g), and large birth weight (BW) (> 4000 g) were associated with kidney disease using 4 different estimating equations. We used the Counahan-Barratt, updated Schwartz, CKiD-U25, and full age spectrum creatinine-based GFR estimating equations to evaluate associations between a history of LBW/VLBW/large BW and reduced kidney function (eGFR < 90 mL/min/1.73 m2) in children. We also assessed blood pressure (BP) using the old and new pediatric hypertension guidelines. RESULTS: Our analysis included 6336 children (age 12-15 years) in NHANES representing over 13 million US individuals. Using the updated Schwartz, the prevalence of reduced kidney function was 30.1% (25.2-35.6) for children born with LBW compared to 22.4% (20.5-24.3) in children with normal BW. Equations yielded different estimates of prevalence of reduced kidney function in LBW from 21.5% for Counahan-Barratt to 35.4% for CKiD-U25. Compared to those with normal BW, participants with LBW and VLBW had a 7.2 and 10.3% higher prevalence of elevated BP and a 2.4 and 14.6% higher prevalence of hypertension, respectively. CONCLUSIONS: Children born with LBW are at higher risk of reduced kidney function and hypertension than previously described. A higher resolution version of the Graphical abstract is available as Supplementary information.

Identification of Novel Genetic Risk Factors for Focal Segmental Glomerulosclerosis in Children: Results From the Chronic Kidney Disease in Children (CKiD) Cohort.

RATIONALE & OBJECTIVE: Focal segmental glomerulosclerosis (FSGS) is a major cause of pediatric nephrotic syndrome, and African Americans exhibit an increased risk for developing FSGS compared with other populations. Predisposing genetic factors have previously been described in adults. Here we performed genomic screening of primary FSGS in a pediatric African American population. STUDY DESIGN: Prospective cohort with case-control genetic association study design. SETTING & PARTICIPANTS: 140 African American children with chronic kidney disease from the Chronic Kidney Disease in Children (CKiD) cohort, including 32 cases with FSGS. PREDICTORS: Over 680,000 common single-nucleotide polymorphisms (SNPs) were tested for association. We also ran a pathway enrichment analysis and a human leucocyte antigen (HLA)-focused association study. OUTCOME: Primary biopsy-proven pediatric FSGS. ANALYTICAL APPROACH: Multivariate logistic regression models. RESULTS: The genome-wide association study revealed 169 SNPs from 14 independent loci significantly associated with FSGS (false discovery rate [FDR]<5%). We observed notable signals for genetic variants within the APOL1 (P=8.6×10-7; OR, 25.8 [95% CI, 7.1-94.0]), ALMS1 (P=1.3×10-7; 13.0% in FSGS cases vs 0% in controls), and FGFR4 (P=4.3×10-6; OR, 24.8 [95% CI, 6.3-97.7]) genes, all of which had previously been associated with adult FSGS, kidney function, or chronic kidney disease. We also highlighted novel, functionally relevant genes, including GRB2 (which encodes a slit diaphragm protein promoting podocyte structure through actin polymerization) and ITGB1 (which is linked to renal injuries). Our results suggest a major role for immune responses and antigen presentation in pediatric FSGS through (1) associations with SNPs in PTPRJ (or CD148, P=3.5×10-7), which plays a role in T-cell receptor signaling, (2) HLA-DRB1∗11:01 association (P=6.1×10-3; OR, 4.5 [95% CI, 1.5-13.0]), and (3) signaling pathway enrichment (P=1.3×10-6). LIMITATIONS: Sample size and no independent replication cohort with genomic data readily available. CONCLUSIONS: Our genetic study has identified functionally relevant risk factors and the importance of immune regulation for pediatric primary FSGS, which contributes to a better description of its molecular pathophysiological mechanisms. PLAIN-LANGUAGE SUMMARY: We assessed the genetic risk factors for primary focal segmental glomerulosclerosis (FSGS) by simultaneously testing over 680,000 genetic markers spread across the genome in 140 children, including 32 with FSGS lesions. Fourteen independent genetic regions were significantly associated with pediatric FSGS, including APOL1 and ALMS1-NAT8, which were previously found to be associated with FSGS and chronic kidney diseases in adults. Novel genes with relevant biological functions were also highlighted, such as GRB2 and FGFR4, which play a role in the kidney filtration barrier and in kidney cell differentiation, respectively. Finally, we revealed the importance of immune regulation in pediatric FSGS through associations involving cell surface proteins presenting antigens to the immune system and interacting with T-cell receptors.

Precision nephrology identified tumor necrosis factor activation variability in minimal change disease and focal segmental glomerulosclerosis.

The diagnosis of nephrotic syndrome relies on clinical presentation and descriptive patterns of injury on kidney biopsies, but not specific to underlying pathobiology. Consequently, there are variable rates of progression and response to therapy within diagnoses. Here, an unbiased transcriptomic-driven approach was used to identify molecular pathways which are shared by subgroups of patients with either minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). Kidney tissue transcriptomic profile-based clustering identified three patient subgroups with shared molecular signatures across independent, North American, European, and African cohorts. One subgroup had significantly greater disease progression (Hazard Ratio 5.2) which persisted after adjusting for diagnosis and clinical measures (Hazard Ratio 3.8). Inclusion in this subgroup was retained even when clustering was limited to those with less than 25% interstitial fibrosis. The molecular profile of this subgroup was largely consistent with tumor necrosis factor (TNF) pathway activation. Two TNF pathway urine markers were identified, tissue inhibitor of metalloproteinases-1 (TIMP-1) and monocyte chemoattractant protein-1 (MCP-1), that could be used to predict an individual's TNF pathway activation score. Kidney organoids and single-nucleus RNA-sequencing of participant kidney biopsies, validated TNF-dependent increases in pathway activation score, transcript and protein levels of TIMP-1 and MCP-1, in resident kidney cells. Thus, molecular profiling identified a subgroup of patients with either MCD or FSGS who shared kidney TNF pathway activation and poor outcomes. A clinical trial testing targeted therapies in patients selected using urinary markers of TNF pathway activation is ongoing.

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.

A review of ferric citrate clinical studies, and the rationale and design of the Ferric Citrate and Chronic Kidney Disease in Children (FIT4KiD) trial.

Pediatric chronic kidney disease (CKD) is characterized by many co-morbidities, including impaired growth and development, CKD-mineral and bone disorder, anemia, dysregulated iron metabolism, and cardiovascular disease. In pediatric CKD cohorts, higher circulating concentrations of fibroblast growth factor 23 (FGF23) are associated with some of these adverse clinical outcomes, including CKD progression and left ventricular hypertrophy. It is hypothesized that lowering FGF23 levels will reduce the risk of these events and improve clinical outcomes. Reducing FGF23 levels in CKD may be accomplished by targeting two key stimuli of FGF23 production-dietary phosphate absorption and iron deficiency. Ferric citrate is approved for use as an enteral phosphate binder and iron replacement product in adults with CKD. Clinical trials in adult CKD cohorts have also demonstrated that ferric citrate decreases circulating FGF23 concentrations. This review outlines the possible deleterious effects of excess FGF23 in CKD, summarizes data from the adult CKD clinical trials of ferric citrate, and presents the Ferric Citrate and Chronic Kidney Disease in Children (FIT4KiD) study, a randomized, placebo-controlled trial to evaluate the effects of ferric citrate on FGF23 in pediatric patients with CKD stages 3-4 (ClinicalTrials.gov Identifier NCT04741646).

Gluten-Free Diet in Childhood Difficult-to-Treat Nephrotic Syndrome: A Pilot Feasibility Study.

Introduction: Minimal change disease in childhood can follow a frequently relapsing or steroid-dependent course in up to 40% of cases. Second-line immunosuppressive medications that are used to manage these patients are associated with significant adverse effects. There is a need for safer alternative treatments for difficult-to-treat nephrotic syndrome. Therefore, we conducted an open-label feasibility study to assess the safety and efficacy of a gluten-free diet as treatment for pediatric patients with difficult-to-treat nephrotic syndrome. As a second aim, we sought to determine if the plasma zonulin concentration can identify those who are more likely to respond to this intervention. Methods: Seventeen patients were placed on a gluten-free diet for 6 months. A positive response was defined as a 50% reduction in the relapse rate compared to the preceding 6 months or the ability to discontinue 1 immunosuppressive drug. Results: Five (29%) participants had a positive response to the dietary intervention. The gluten-free diet was well tolerated with no clinical or laboratory adverse events. Plasma zonulin concentration was elevated in patients who failed to benefit from the gluten-free diet. Discussion/Conclusion: A gluten-free diet may be a useful adjunctive intervention for patients with difficult-to-treat nephrotic syndrome that can be implemented prior to resorting to second-line immunosuppressive therapy. Development of the plasma zonulin level as a biomarker to predict efficacy would facilitate rational use of a gluten-free diet in the management of nephrotic syndrome.

Association of early dysnatremia with mortality in the neonatal intensive care unit: results from the AWAKEN study.

OBJECTIVE: To determine the association of dysnatremia in the first postnatal week and risk of acute kidney injury (AKI) and mortality. STUDY DESIGN: A secondary analysis of 1979 neonates in the AWAKEN cohort evaluated the association of dysnatremia with (1) AKI in the first postnatal week and (2) mortality, utilizing time-varying Cox proportional hazard models. RESULT: Dysnatremia developed in 50.2% of the cohort and was not associated with AKI. Mortality was associated with hyponatremia (HR 2.15, 95% CI 1.07-4.31), hypernatremia (HR 4.23, 95% CI 2.07-8.65), and combined hypo/hypernatremia (HR 6.39, 95% CI 2.01-14.01). In stratified models by AKI-status, hypernatremia and hypo/hypernatremia increased risk of mortality in neonates without AKI. CONCLUSION: Dysnatremia within the first postnatal week was associated with increased risk of mortality. Hypernatremia and combined hypo/hypernatremia remained significantly associated with mortality in neonates without AKI. This may reflect fluid strategies kidney injury independent of creatinine and urine-output defined AKI, and/or systemic inflammation.

Patterns of recombinant growth hormone therapy use and growth responses among children with chronic kidney disease.

BACKGROUND: Recombinant growth hormone (rGH) is an efficacious therapy for growth failure in children with chronic kidney disease (CKD). We described rGH use and estimated its relationship with growth and kidney function in the Chronic Kidney Disease in Children (CKiD) cohort. METHODS: Participants included those with growth failure, prevalent rGH users, and rGH initiators who did not meet growth failure criteria. Among those with growth failure, height z scores and GFR were compared between rGH initiators and non-initiators across 42 months. Inverse probability weights accounted for differences in baseline variables in weighted linear regressions. RESULTS: Among 148 children with growth failure and no previous rGH therapy, 42 (28%) initiated rGH therapy. Of the initiators, average age was 8.9 years, height z score was 2.50 standard deviations (SDs) (0.6th percentile), and GFR was 44 ml/min/1.73m2. They were compared to 106 children with growth failure who never initiated therapy (8.8 years, -2.33 SDs, and 51 ml/min/1.73m2). At 30 and 42 months after rGH, height increased +0.26 (95%CI: -0.11, +0.62) and +0.35 (95%CI: -0.17, +0.87) SDs, respectively, relative to those who did not initiate rGH. rGH was not associated with GFR. CONCLUSIONS: Participants with growth failure receiving rGH experienced significant growth, although this was attenuated relative to RCTs, and were more likely to have higher household income and lower GFR. A substantial number of participants, predominantly boys, without diagnosed growth failure received rGH and had the highest achieved height relative to mid-parental height. Since rGH was not associated with accelerated GFR decline, increasing rGH use in this population is warranted.

Assessing the integrity of auditory processing and sensory memory in adults with cystinosis (CTNS gene mutations).

BACKGROUND: Cystinosis, a rare lysosomal storage disease, is characterized by cystine crystallization and accumulation within tissues and organs, including the kidneys and brain. Its impact on neural function appears mild relative to its effects on other organs, but therapeutic advances have led to substantially increased life expectancy, necessitating deeper understanding of its impact on neurocognitive function in adulthood. We previously demonstrated intact auditory sensory processing, accompanied by mild sensory memory difficulties, in children and adolescents with cystinosis. METHODS: We investigated whether further progressive decrements in these processes would be observed in adults with cystinosis, comparing high-density auditory-evoked potential (AEP) recordings from adults with cystinosis (N = 15; ages: 19-38 years) to those of age-matched controls (N = 17). We employed a duration oddball paradigm with different stimulation rates, in which participants passively listened to regularly occurring standard tones interspersed with infrequently occurring deviant tones. Analyses focused on AEP components reflecting auditory sensory-perceptual processing (N1 and P2), sensory memory (mismatch negativity, MMN), and attentional orienting (P3a). RESULTS: Overall, adults with cystinosis produced highly similar sensory-perceptual AEP responses to those observed in controls suggesting intact early auditory cortical processing. However, significantly increased P2 and P3a amplitudes and reduced MMN at slower stimulation rates were observed, suggesting mild-to-moderate changes in auditory sensory memory and attentional processing. While cognitive testing revealed lower scores on verbal IQ and perceptual reasoning in cystinosis, these did not correlate with the AEP measures. CONCLUSIONS: These neurophysiological data point to the emergence of subtle auditory processing deficits in early adulthood in cystinosis, warranting further investigation of memory and attentional processes in this population, and of their consequences for perceptual and cognitive function.

APOL1 genotype-associated morphologic changes among patients with focal segmental glomerulosclerosis.

BACKGROUND: The G1 and G2 alleles of apolipoprotein L1 (APOL1) are common in the Black population and associated with increased risk of focal segmental glomerulosclerosis (FSGS). The molecular mechanisms linking APOL1 risk variants with FSGS are not clearly understood, and APOL1's natural absence in laboratory animals makes studying its pathobiology challenging. METHODS: In a cohort of 90 Black patients with either FSGS or minimal change disease (MCD) enrolled in the Nephrotic Syndrome Study Network (58% pediatric onset), we used kidney biopsy traits as an intermediate outcome to help illuminate tissue-based consequences of APOL1 risk variants and expression. We tested associations between APOL1 risk alleles or glomerular APOL1 mRNA expression and 83 light- or electron-microscopy traits measuring structural and cellular kidney changes. RESULTS: Under both recessive and dominant models in the FSGS patient subgroup (61%), APOL1 risk variants were significantly correlated (defined as FDR <0.1) with decreased global mesangial hypercellularity, decreased condensation of cytoskeleton, and increased tubular microcysts. No significant correlations were detected in MCD cohort. Independent of risk alleles, glomerular APOL1 expression in FSGS patients was not correlated with morphologic features. CONCLUSIONS: While APOL1-associated FSGS is associated with two risk alleles, both one and two risk alleles are associated with cellular/tissue changes in this study of FSGS patients. Our lack of discovery of a large group of tissue differences in FSGS and no significant difference in MCD may be due to the lack of power but also supports investigating whether machine learning methods may more sensitively detect APOL1-associated changes.

Analysis of Active and Passive Tobacco Exposures and Blood Pressure in US Children and Adolescents.

Importance: Hypertension is a leading cause of cardiovascular disease in adults; preclinical associations between hypertension and cardiovascular disease are seen in childhood. Nicotine is a known toxin, but its association with pediatric hypertension is unclear. Objective: To test the hypothesis that tobacco exposure is associated with the presence of elevated blood pressure in US children and adolescents and that this association is dose dependent. Design, Setting, and Participants: This cross-sectional study used data from the 2007 to 2016 National Health and Nutrition Examination Survey (NHANES), a population-based nationally representative sample of US children and adolescents. Children were eligible if they were aged 8 to 19 years at the time of participation in the main NHANES study. Exclusion criteria included those of the main NHANES study, inability to complete testing, or missing questionnaires. Of the 10 143 participants in NHANES aged 8 to 19 during the study years, 8520 were included in the analysis. Analysis was conducted from October 12, 2019, to July 9, 2020. Exposures: Tobacco exposure, defined as serum cotinine levels greater than 0.05 µg/L, or reporting living with a smoker or smoking themselves. Main Outcomes and Measures: Elevated blood pressure, classified as greater than 90% for a child's age, sex, and height according to the 2017 American Academy of Pediatrics Clinical Practice Guidelines. The a priori hypothesis that there is a positive association between tobacco exposure and elevated blood pressure in the study population was tested. Analysis included logistic regression with adjustment for possible confounders. Subgroup and sensitivity analyses were conducted. Results: A total of 8520 children were included in the analysis, representing 41 million US children. The mean (SD) age of the participants was 13.1 (0.05) years, 51% (95% CI, 49%-52%) were male, and 58% (95% CI, 54%-62%) were non-Hispanic White individuals. Participants with any tobacco smoke exposure were more likely than those without exposure to be older (mean [SD] age, 13.3 [0.07] years vs 12.8 [0.06] years), male (53% [95% CI, 51%-55%] vs 49% [95% CI, 47%-50%]), and non-Hispanic Black individuals (19% [95% CI, 16%-22%] vs 10% [95% CI, 8%-12%]). The odds of having elevated blood pressure was 1.31 (95% CI, 1.06-1.61) for any tobacco exposure after adjustment; odds were similar across subgroups and remained significant in multiple sensitivity analyses. Conclusions and Relevance: This study suggests that tobacco exposure is associated with elevated blood pressure in US children and adolescents. This modifiable risk factor represents a target for further research into reducing hypertension in children and adolescents.

Longitudinal outcomes of body mass index in overweight and obese children with chronic kidney disease.

BACKGROUND: Longitudinal changes in body mass index (BMI) among overweight and obese children with chronic kidney disease (CKD) are not well characterized. We studied longitudinal trajectories and correlates of these trajectories, as results may identify opportunities to optimize health outcomes. METHODS: Longitudinal changes in age-sex-specific BMI z-scores over 1851 person-years of follow-up were assessed in 524 participants of the Chronic Kidney Disease in Children Study. A total of 353 participants were categorized as normal (BMI > 5th to < 85th percentile), 56 overweight (BMI ≥ 85th to 95th percentile) and 115 obese (BMI ≥ 95th percentile) based on the average of three BMI measurements during the first year of follow-up. Studied covariates included age, sex, race, CKD etiology, corticosteroid usage, household income, and maternal education. RESULTS: In unadjusted analysis, BMI z-scores decreased over time in elevated BMI groups (overweight: mean = - 0.06 standard deviations (SD) per year, 95% CI: - 0.11, - 0.01; obese: mean = - 0.04 SD per year, 95% CI: - 0.07, - 0.01). Among obese children, only age was associated with change in BMI z-score; children < 6 years had a mean decrease of 0.19 SD during follow-up (95% CI: - 0.30, - 0.09). Socioeconomic factors were not associated with change in BMI. CONCLUSION: Overweight and obese children with CKD demonstrated a significant annual decline in BMI, though the absolute change was modest. Among obese children, only age < 6 years was associated with significant decline in BMI. Persistence of elevated BMI in older children and adolescents with CKD underscores the need for early prevention and effective intervention.

COVID-19 in Children With Kidney Disease: A Report of 2 Cases.

The presentation of novel coronavirus disease 2019 (COVID-19) in children with kidney disease is largely unknown. We report on 2 children with kidney disease not receiving long-term immunosuppression who were hospitalized due to COVID-19. The first case is an infant with end-stage kidney disease secondary to bilateral cystic dysplastic kidneys and posterior urethral valves receiving peritoneal dialysis, with a history of prematurity previously requiring mechanical ventilation in the neonatal intensive care unit, who presented with fever, hypertension, and emesis. He had no respiratory symptoms and recovered with supportive care. His hypertension was managed well with amlodipine. The second case is a child with steroid-sensitive nephrotic syndrome who presented with a relapse of nephrotic syndrome with concurrent peritonitis and sepsis caused by Streptococcus agalactiae. He was treated with antibiotics and prophylactic anticoagulation therspy. Steroid therapy was initiated after 48 hours of antibiotic therapy. Neither child required mechanical ventilation or developed COVID-19-related multisystem inflammatory syndrome.

Proteinuria Reduction and Kidney Survival in Focal Segmental Glomerulosclerosis.

RATIONALE & OBJECTIVE: Remission of proteinuria has been shown to be associated with lower rates of kidney disease progression among people with focal segmental glomerulosclerosis (FSGS). The goal of this study was to evaluate whether reductions in proteinuria after treatment are associated with greater kidney survival. STUDY DESIGN: Cohort analysis of clinical trial participants. SETTING & PARTICIPANTS: Patients with steroid-resistant FSGS enrolled in a randomized treatment trial that compared cyclosporine with mycophenolate mofetil plus dexamethasone. PREDICTORS: Reduction in proteinuria measured during 26 weeks after initiating treatment. OUTCOMES: Repeated assessments of estimated glomerular filtration rate (eGFR) and time to a composite outcome of kidney failure or death assessed between 26 weeks and 54 months after randomization. ANALYTICAL APPROACH: Multivariable linear mixed-effects models with participant-specific slope and intercept to estimate the association of change in proteinuria over 26 weeks while receiving treatment with the subsequent slope of change in eGFR. Multivariable time-varying Cox proportional hazards models were used to estimate the association of changes in proteinuria with time to the composite outcome. RESULTS: 138 of 192 trial participants were included. Changes in proteinuria over 26 weeks were significantly related to eGFR slope. A 1-unit reduction in log-transformed urinary protein-creatinine ratio was associated with a 3.90mL/min/1.73m2 per year increase in eGFR (95% CI, 2.01-5.79). This difference remained significant after adjusting for complete remission. There was an analogous relationship between time-varying proteinuria and time to the composite outcome: the HR per 1-unit reduction in log-transformed urinary protein-creatinine ratio was 0.23 (95% CI, 0.12-0.44). LIMITATIONS: Limited to individuals with steroid-resistant FSGS followed up for a maximum of 5 years. CONCLUSIONS: These findings provide evidence for the benefit of urinary protein reduction in FSGS. Reductions in proteinuria warrant further evaluation as a potential surrogate for preservation of kidney function that may inform the design of future clinical trials.

The longitudinal relationship between patient-reported outcomes and clinical characteristics among patients with focal segmental glomerulosclerosis in the Nephrotic Syndrome Study Network.

BACKGROUND: Understanding the relationship between clinical and patient-reported outcomes (PROs) will help support clinical care and future clinical trial design of novel therapies for focal segmental glomerulosclerosis (FSGS). METHODS: FSGS patients ≥8 years of age enrolled in the Nephrotic Syndrome Study Network completed Patient-Reported Outcomes Measurement Information System PRO measures of health-related quality of life (HRQoL) (children: global health, mobility, fatigue, pain interference, depression, anxiety, stress and peer relationships; adults: physical functioning, fatigue, pain interference, sleep impairment, mental health, depression, anxiety and social satisfaction) at baseline and during longitudinal follow-up for a maximum of 5 years. Linear mixed-effects models were used to determine which demographic, clinical and laboratory features were associated with PROs for each of the eight children and eight adults studied. RESULTS: There were 45 children and 114 adult FSGS patients enrolled that had at least one PRO assessment and 519 patient visits. Multivariable analyses among children found that edema was associated with global health (-7.6 points, P = 0.02) and mobility (-4.2, P = 0.02), the number of reported symptoms was associated with worse depression (-2.7 per symptom, P = 0.009) and anxiety (-2.3, P = 0.02) and the number of emergency room (ER) visits in the prior 6 months was associated with worse mobility (-2.8 per visit, P < 0.001) and fatigue (-2.4, P = 0.03). Multivariable analyses among adults found the number of reported symptoms was associated with worse function in all eight PROMIS measures and the number of ER visits was associated with worse fatigue, pain interference, sleep impairment, depression, anxiety and social satisfaction. Laboratory markers of disease severity (i.e. proteinuria, estimated glomerular filtration rate and serum albumin) did not predict PRO in multivariable analyses, with the single exception of complete remission and better pain interference scores among children (+9.3, P = 0.03). CONCLUSIONS: PROs provide important information about HRQoL for persons with FSGS that is not captured solely by the examination of laboratory-based markers of disease. However, it is critical that instruments capture the patient experience and FSGS clinical trials may benefit from a disease-specific instrument more sensitive to within-patient changes.

Low Serum Bicarbonate and CKD Progression in Children.

BACKGROUND AND OBJECTIVES: Studies of adults have demonstrated an association between metabolic acidosis, as measured by low serum bicarbonate levels, and CKD progression. We evaluated this relationship in children using data from the Chronic Kidney Disease in Children study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: The relationship between serum bicarbonate and a composite end point, defined as 50% decline in eGFR or KRT, was described using parametric and semiparametric survival methods. Analyses were stratified by underlying nonglomerular and glomerular diagnoses, and adjusted for demographic characteristics, eGFR, proteinuria, anemia, phosphate, hypertension, and alkali therapy. RESULTS: Six hundred and three participants with nonglomerular disease contributed 2673 person-years of follow-up, and 255 with a glomerular diagnosis contributed 808 person-years of follow-up. At baseline, 39% (237 of 603) of participants with nonglomerular disease had a bicarbonate level of ≤22 meq/L and 36% (85 of 237) of those participants reported alkali therapy treatment. In participants with glomerular disease, 31% (79 of 255) had a bicarbonate of ≤22 meq/L, 18% (14 of 79) of those participants reported alkali therapy treatment. In adjusted longitudinal analyses, compared with participants with a bicarbonate level >22 meq/L, hazard ratios associated with a bicarbonate level of <18 meq/L and 19-22 meq/L were 1.28 [95% confidence interval (95% CI), 0.84 to 1.94] and 0.91 (95% CI, 0.65 to 1.26), respectively, in children with nonglomerular disease. In children with glomerular disease, adjusted hazard ratios associated with bicarbonate level ≤18 meq/L and bicarbonate 19-22 meq/L were 2.16 (95% CI, 1.05 to 4.44) and 1.74 (95% CI, 1.07 to 2.85), respectively. Resolution of low bicarbonate was associated with a lower risk of CKD progression compared with persistently low bicarbonate (≤22 meq/L). CONCLUSIONS: In children with glomerular disease, low bicarbonate was linked to a higher risk of CKD progression. Resolution of low bicarbonate was associated with a lower risk of CKD progression. Fewer than one half of all children with low bicarbonate reported treatment with alkali therapy. Long-term studies of alkali therapy's effect in patients with pediatric CKD are needed.

Urinary Epidermal Growth Factor as a Marker of Disease Progression in Children With Nephrotic Syndrome.

INTRODUCTION: Childhood-onset nephrotic syndrome has a variable clinical course. Improved predictive markers of long-term outcomes in children with nephrotic syndrome are needed. This study tests the association between baseline urinary epidermal growth factor (uEGF) excretion and longitudinal kidney function in children with nephrotic syndrome. METHODS: The study evaluated 191 participants younger than 18 years enrolled in the Nephrotic Syndrome Study Network, including 118 with their first clinically indicated kidney biopsy (68 minimal change disease; 50 focal segmental glomerulosclerosis) and 73 with incident nephrotic syndrome without a biopsy. uEGF was measured at baseline for all participants and normalized by the urine creatinine (Cr) concentration. Renal epidermal growth factor (EGF) mRNA was measured in the tubular compartment microdissected from kidney biopsy cores from a subset of patients. Linear mixed models were used to test if baseline uEGF/Cr and EGF mRNA expression were associated with change in estimated glomerular filtration rate (eGFR) over time. RESULTS: Higher uEGF/Cr at baseline was associated with slower eGFR decline during follow-up (median follow-up = 30 months). Halving of uEGF/Cr was associated with a decrease in eGFR slope of 2.0 ml/min per 1.73 m2 per year (P < 0.001) adjusted for age, race, diagnosis, baseline eGFR and proteinuria, and APOL1 genotype. In the biopsied subgroup, uEGF/Cr was correlated with EGF mRNA expression (r = 0.74; P < 0.001), but uEGF/Cr was retained over mRNA expression as the stronger predictor of eGFR slope after multivariable adjustment (decrease in eGFR slope of 1.7 ml/min per 1.73 m2 per year per log2 decrease in uEGF/Cr; P < 0.001). CONCLUSION: uEGF/Cr may be a useful noninvasive biomarker that can assist in predicting the long-term course of kidney function in children with incident nephrotic syndrome.

Grip strength in children with chronic kidney disease.

BACKGROUND: The relationship between muscle strength and chronic kidney disease (CKD) in children is unknown. This study aims to quantify the association between grip strength (GS) and kidney function and to explore factors associated with grip strength in children and adolescents with CKD. METHODS: We included 411 children (699 GS assessments) of the Chronic Kidney Disease in Children (CKiD) study. They were matched by age, sex, and height to a healthy control from the National Health and Nutrition Examination Survey to quantify the relationship between GS and CKD. Linear mixed models were used to identify factors associated with GS among CKD patients. RESULTS: Median GS z-score was - 0.72 (IQR - 1.39, 0.11) among CKD patients with CKD stages 2 through 5 having significantly lower GS than CKD stage 1. Compared with healthy controls, CKiD participants had a decreased GS z-score (- 0.53 SD lower, 95% CI - 0.67 to - 0.39) independent of race/ethnicity and body mass index. Factors associated with reduced GS included longer duration of CKD, pre-pubertal status, delayed puberty, neuropsychiatric comorbidities, need of feeding support, need for alkali therapy, and hemoglobin level. Decreased GS was also associated with both a lower frequency and intensity of physical activity. CONCLUSIONS: CKD is associated with impaired muscle strength in children independent of growth retardation and BMI. Exposure to CKD for a prolonged time is associated with impaired muscle strength. Potential mediators of the impact of CKD on muscle strength include growth retardation, acidosis, poor nutritional status, and low physical activity. Additional studies are needed to assess the efficacy of interventions targeted at these risk factors.