Normalization of glomerular filtration rate in obese children

Role of metabolic dysfunction-associated steatotic liver disease and of its genetics on kidney function in childhood obesity

OBJECTIVES

Evidence linked metabolic associated steatotic liver disease (MASLD) to kidney damage with the potential contribution of the I148M variant of the Patatin-like phospholipase containing domain 3 (PNPLA3) gene. We aimed at investigating the relationship of MASLD and of its genetics with kidney function in children with obesity.

METHODS

A comprehensive evaluation including genotyping for the I148M PNPLA3 polymorphism was performed in 1037 children with obesity. Fatty liver (FL) was assessed by liver ultrasound. According to MASLD criteria, subjects with obesity but without FL were included in group 1, while patients with obesity and FL (encompassing one MASLD criterion) were clustered into group 2. Group 3 included patients with obesity, FL, and metabolic dysregulation (encompassing >1 MASLD criterion).

RESULTS

Alanine transaminase levels significantly increased while estimated glomerular filtration rate (eGFR) significantly reduced from group 1 to 3. Group 3 showed a higher percentage of carriers of the I148M allele of the PNPLA3 gene compared to other groups (p < 0.0001). Carriers of group 2 and of group 3 showed reduced eGFR levels than noncarriers of group 2 (p = 0.04) and of group 3 (p = 0.02), respectively. A general linear model for eGFR variance in the study population showed an inverse association of eGFR with both MASLD and PNPLA3 genotypes (p = 0.011 and p = 0.02, respectively). An inverse association of eGFR with MASLD was also confirmed only in carriers (p = 0.006).

CONCLUSIONS

The coexistence of more than 1 MASLD criterion in children with obesity seems to adversely affect kidney function. The PNPLA3 I148M allele further impacts on this association.

Role of subclinical hypothyroidism on kidney damage in children with obesity

BACKGROUND/OBJECTIVES

The interplay of subclinical hypothyroidism (SH) with obesity has been well-documented, while an intriguing but still controversial association with kidney damage (KD) has recently emerged. Given the heightened cardiometabolic risk inherent to pediatric obesity, this might further impact on the overall health of children with obesity. Therefore, we aimed at evaluating the impact of SH on KD in children with obesity.

SUBJECTS/METHODS

We retrospectively examined 355 children with obesity stratified according to presence or absence of SH. KD was defined as reduced estimated glomerular filtration rate (eGFR<90 mL/min/1.73 m2) and/or hypertension, and/or albuminuria (≥30 mg/g urinary creatinine), while SH was defined by thyroid stimulating hormone (TSH) > 4.5μ UI/ml with normal free triiodothyronine and free thyroxine levels.

RESULTS

Children with SH showed a higher KD prevalence than those without SH (p = 0.004). They also had lower eGFR levels than their counterparts without SH (p = 0.001) and showed an adjusted OR to have KD of 2.04 (95% CI: 1.15-3.61; p = 0.015). A general linear model for eGFR variance showed an inverse association of eGFR with TSH levels (p < 0.0001).

CONCLUSIONS

Although preliminary, our data suggested an increased risk of KD in children with obesity and SH.

The Impact of Paediatric Obesity on Drug Pharmacokinetics: A Virtual Clinical Trials Case Study with Amlodipine

The incidence of paediatric obesity continues to rise worldwide and contributes to a range of diseases including cardiovascular disease. Obesity in children has been shown to impact upon the plasma concentrations of various compounds, including amlodipine. Nonetheless, information on the influence of obesity on amlodipine pharmacokinetics and the need for dose adjustment has not been studied previously. This study applied the physiologically based pharmacokinetic modelling and established a paediatric obesity population to assess the impact of obesity on amlodipine pharmacokinetics in children and explore the possible dose adjustments required to reach the same plasma concentration as non-obese paediatrics. The difference in predicted maximum concentration (Cmax) and area under the curve (AUC) were significant between children with and without obesity across the age group 2 to 18 years old when a fixed-dose regimen was used. On the contrary, a weight-based dose regimen showed no difference in Cmax between obese and non-obese from 2 to 9 years old. Thus, when a fixed-dose regimen is to be administered, a 1.25- to 1.5-fold increase in dose is required in obese children to achieve the same Cmax concentration as non-obese children, specifically for children aged 5 years and above.

Kidney damage predictors in children with metabolically healthy and metabolically unhealthy obesity phenotype

BACKGROUND

Obesity and kidney damage have been closely linked in adults, but little is still known in childhood.

OBJECTIVE

To identify predictors of kidney damage in children with metabolically healthy (MHO) and metabolically unhealthy (MUO) obesity phenotypes.

METHODS

We retrospectively examined 396 children with obesity (mean age 10.72 ± 2.71 years, body mass index-standard deviation score, BMI-SDS, 2.23 ± 0.57) stratified according to metabolic phenotypes. Kidney damage was defined as the presence of reduced estimated glomerular filtration rate (eGFR < 90 mL/min/1.73m2) and/or albuminuria (≥ 30 mg/g urinary creatinine).

RESULTS

Kidney damage was found in 20.9% of the study population. Children with kidney damage had higher BMI-SDS, homeostasis model assessment of insulin resistance (HOMA-IR), and inflammation markers levels and increased prevalence of non-alcoholic fatty liver disease (NAFLD) than those without kidney damage (all p < 0.005). MUO and MHO subjects had respectively an odds ratio (OR) to show kidney damage of of 1.92 (95%CI:1.22-3.01; p = 0.005) and 1.05 (95%CI:1.00-1.09; p = 0.028) after adjustments. Moreover, we found that only HOMA-IR was closely associated to kidney damage in MUO group (OR = 2.07;95%CI:1.20-3.57; p = 0.007), while HOMA-IR (OR = 1.15;95%CI:1.02-1.29; p = 0.011) and uric acid (OR = 1.15;95% CI:1.02-1.30; p = 0.010) were the only significant risk factors for kidney damage in MHO group.

CONCLUSION

An increased risk of kidney damage has been observed in children with obesity and in particular in those with MUO phenotype. As their role on kidney function, HOMA-IR should be monitored in MUO children and both HOMA-IR and uric acid in MHO children.

PNPLA3 I148M Polymorphism Influences Renal Function in Children With Obesity and Prediabetes

OBJECTIVE

Nonalcoholic fatty liver disease negatively impacts on renal function with the contribution of the I148 M variant in the patatin-like phospholipase-containing domain 3 (PNPLA3) gene. We hypothesized that children with prediabetes present with a lower estimated glomerular filtration rate (eGFR) than those with normal glucose tolerance (NGT) and that the 148M PNPLA3 allele could play a worsening role. We aimed evaluating the influence of the I148 M PNPLA3 polymorphism on the relationship between the eGFR and prediabetes in children with obesity.

METHODS

One thousand thirty-six children underwent to complete assessment and were genotyped for the I148 M PNPLA3 polymorphism.

RESULTS

Patients with prediabetes showed lower eGFR levels (171.03 ± 40.32 vs. 190.80 ± 41.71 mL/min/1.73 m2; P = .001) and higher prevalence of nonalcoholic fatty liver disease (80% vs. 59%; P = .003) than those with NGT. Children with prediabetes showed lower eGFR levels than those with NGT (150.97 ± 14.56 vs. 192.88 ± 40.09; P < .0001) among carriers of the PNPLA3 148M allele. This was not confirmed among patients homozygous for the PNPLA3 I148 allele. A general linear model for eGFR variance confirmed an inverse and significant association of the eGFR with prediabetes in patients carrying the 148M PNPLA3 allele but not in patients homozygous for the PNPLA3 I148 allele.

CONCLUSIONS

Prediabetes negatively affects renal function in children with obesity. This effect is heightened in patients carrying the PNPLA3 148M allele.

Characterizing Pharmacokinetics in Children With Obesity-Physiological, Drug, Patient, and Methodological Considerations

Childhood obesity is an alarming public health problem. The pediatric obesity rate has quadrupled in the past 30 years, and currently nearly 20% of United States children and 9% of children worldwide are classified as obese. Drug distribution and elimination processes, which determine drug exposure (and thus dosing), can vary significantly between patients with and without obesity. Obesity-related physiological changes, such as increased tissue volume and perfusion, altered blood protein concentrations, and tissue composition can greatly affect a drug's volume of distribution, which might necessitate adjustment in loading doses. Obesity-related changes in the drug eliminating organs, such as altered enzyme activity in the liver and glomerular filtration rate, can affect the rate of drug elimination, which may warrant an adjustment in the maintenance dosing rate. Although weight-based dosing (i.e., in mg/kg) is commonly practiced in pediatrics, choice of the right body size metric (e.g., total body weight, lean body weight, body surface area, etc.) for dosing children with obesity still remains a question. To address this gap, the interplay between obesity-related physiological changes (e.g., altered organ size, composition, and function), and drug-specific properties (e.g., lipophilicity and elimination pathway) needs to be characterized in a quantitative framework. Additionally, methodological considerations, such as adequate sample size and optimal sampling scheme, should also be considered to ensure accurate and precise top-down covariate selection, particularly when designing opportunistic studies in pediatric drug development. Further factors affecting dosing, including existing dosing recommendations, target therapeutic ranges, dose capping, and formulations constraints, are also important to consider when undergoing dose selection for children with obesity. Opportunities to bridge the dosing knowledge gap in children with obesity include modeling and simulating techniques (i.e., population pharmacokinetic and physiologically-based pharmacokinetic [PBPK] modeling), opportunistic clinical data, and real world data. In this review, key considerations related to physiology, drug parameters, patient factors, and methodology that need to be accounted for while studying the influence of obesity on pharmacokinetics in children are highlighted and discussed. Future studies will need to leverage these modeling opportunities to better describe drug exposure in children with obesity as the childhood obesity epidemic continues.

Development and Evaluation of a Virtual Population of Children with Obesity for Physiologically Based Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVE

While one in five children in the USA are now obese, and more than three-quarters receive at least one drug during childhood, there is limited dosing guidance for this vulnerable patient population. Physiologically based pharmacokinetic modeling can bridge the gap in the understanding of how pharmacokinetics, including drug distribution and clearance, changes with obesity by incorporating known obesity-related physiological changes in children. The objective of this study was to develop a virtual population of children with obesity to enable physiologically based pharmacokinetic modeling, then use the novel virtual population in conjunction with previously developed models of clindamycin and trimethoprim/sulfamethoxazole to better understand dosing of these drugs in children with obesity.

METHODS

To enable physiologically based pharmacokinetic modeling, a virtual population of children with obesity was developed using national survey, electronic health record, and clinical trial data, as well as data extracted from the literature. The virtual population accounts for key obesity-related changes in physiology relevant to pharmacokinetics, including increased body size, body composition, organ size and blood flow, plasma protein concentrations, and glomerular filtration rate. The virtual population was then used to predict the pharmacokinetics of clindamycin and trimethoprim/sulfamethoxazole in children with obesity using previously developed physiologically based pharmacokinetic models.

RESULTS

Model simulations predicted observed concentrations well, with an overall average fold error of 1.09, 1.24, and 1.53 for clindamycin, trimethoprim, and sulfamethoxazole, respectively. Relative to children without obesity, children with obesity experienced decreased clindamycin and trimethoprim/sulfamethoxazole weight-normalized clearance and volume of distribution, and higher absolute doses under recommended pediatric weight-based dosing regimens.

CONCLUSIONS

Model simulations support current recommended weight-based dosing in children with obesity for clindamycin and trimethoprim/sulfamethoxazole, as they met target exposure despite these changes in clearance and volume of distribution.

Creatinine-based GFR-estimating equations in children with overweight and obesity

BACKGROUND

With the increasing prevalence of childhood obesity and related development of chronic kidney disease (CKD), there is a critical need to understand how best to assess kidney function in children with obesity. Since serum creatinine (SCr) is recommended as marker of first choice for GFR estimation, we evaluated and compared creatinine-based GFR equations in children with overweight and obesity.

METHODS

Six hundred children with overweight and obesity (53.5% female; mean age 12.20 ± 3.28 years; mean BMI z-score 3.31 ± 0.75) were included from the Centre for Overweight Adolescent and Children's Healthcare (COACH).

RESULTS

Serum creatinine (SCr), normalized using Q-age polynomials obtained from reference values, results in median and mean SCr/Q value close to "1" for all age groups, and 96.5% of the children have a SCr/Q within the reference band [0.67-1.33], corresponding to the 2.5th and 97.5th percentile. eGFR CKiD (bedside Schwartz equation) and Schwartz-Lyon decreased with age, whereas eGFR EKFC and modified CKD-EPI40 showed no age-dependency, but the distribution of eGFR values was not symmetrical. eGFR CKiD under 25 (CKiDU25) demonstrated no age-dependency but major sex differences were observed. eGFR FAS age, FAS height, and adjusted-creatinine revised Lund-Malmö (LMR18) showed a relatively symmetrical distribution and no age-dependency.

CONCLUSIONS

Serum creatinine (SCr) values of children with overweight and obesity are mostly within the reference range for children. Normalization of SCr using reference Q-age polynomials works very well in this cohort. After evaluation of the different equations, we suggest that FAS age, FAS height, and LMR18 are the preferred creatinine-based GFR-estimating equations in children with overweight and obesity.

CLINICALTRIAL

gov; Registration Number: NCT02091544. A higher resolution version of the Graphical abstract is available as Supplementary information.

Obesity Facts and Their Influence on Renal Function Across the Life Span

Obesity is a chronic disease, with a rapidly increasing prevalence worldwide. Body mass index (BMI) provides the most useful population-level measure of overweight and obesity. For adults, overweight is defined as a BMI (Kg/m²) ≥ 25, and obesity as a BMI ≥ 30, for non-Asians and ≥ 27.5 for Asians. Abdominal obesity can be defined as a waist circumference equal to or higher than 102 cm for men and ≥88 cm for women. The definition of children and adolescents BMI changes with age and sex. Obesity may be exogenous or endogenous obesity, the latter is multifactorial and predominantly manifested during childhood. Presently, overweight and obesity are linked to more deaths worldwide than underweight. The total kidney glomerular filtration rate (GFR) is determined by the sum of nephrons and the GFR within each nephron or single nephron GFR. In clinical practice, GFR is more frequently calculated by GFR estimating equations based upon the plasma levels of creatinine, cystatin C, or both. The measured value of plasma creatinine is strongly influenced by non-GFR factors, by its tubular and gastrointestinal secretion, and by the problems associated with the lack of standardization of creatinine's laboratory assay discrediting it as an ideal GFR biomarker. Unlike creatinine, cystatin C plasma levels are mainly determined by GFR. Obesity may affect the kidney, via development of systemic arterial hypertension and/or diabetes mellitus, or directly, by ectopic accumulation of adipose tissue in the kidney. As obesity is a clinical condition associated with altered body composition, creatinine may not be the ideal biomarker for GFR measurement in obese individuals.

Relation of glomerular filtration to insulin resistance and related risk factors in obese children

BACKGROUND AND OBJECTIVE

Childhood obesity is associated with later development of significant renal morbidity. We evaluated the impact of the degree of insulin sensitivity on estimated glomerular filtration rate (eGFR) and determined the factors associated with eGFR in obese children. We further tested the relation of eGFR to clinical outcomes such as blood pressure and microalbuminuria.

MATERIALS AND METHODS

We evaluated the relation of whole body insulin sensitivity and estimated glomerular filtration rate (eGFR) across the spectrum of obesity in children and adolescents. eGFR was calculated using the iCARE formula, which has been validated in obese children with varying glucose tolerance.

RESULTS

1080 children and adolescents with overweight and obesity (701 females and 379 males) participated. Insulin sensitivity was a strongly negatively associated with (B = -2.72, p < 0.001) eGFR), even after adjustment for potential confounders. Male sex emerged to be significantly associated with eGFR with boys having greater values than girls (B = 18.82, p < 0.001). Age was a positively associated (B = 2.86, p < 0.001) with eGFR. Whole body and hepatic insulin sensitivity decreased across eGFR quartiles. Adjusted eGFR was tightly positively associated with systolic blood pressure (B = 0.09, p = 0.003) and negatively associated with the presence of microalbuminuria (B = -2.18, p = 0.04).

CONCLUSIONS

eGFR tends to increase with greater degrees of insulin resistance in children and adolescents representing hyperfiltration and is associated with cardiovascular risk factors. Longitudinal studies are needed to determine the natural history of childhood insulin resistance related hyperfiltration in regards to future kidney disease.

Renal length z-score for the detection of dysfunction in children with solitary functioning kidney

AIM

To evaluate whether renal length z-scores predict renal dysfunction in children with a solitary functioning kidney (SFK).

METHODS

In a single-centre retrospective cohort of children with SFK, we correlated body mass index z-scores, extracellular volume and lean body mass to renal length z-scores. We grouped these z-scores to other markers of renal dysfunction (proteinuria, hypertension, extracellular volume and abnormal estimated glomerular function rate [eGFR]) and analysed renal length z-score with multivariate analysis, receiver-operated characteristics (ROC) plots and Youden's index to determine an appropriate cut-off.

RESULTS

111 children had a median follow-up 5.08 years, eGFR 80.8 mL/min/1.73 m² , and age at last follow-up 7.4 (3.8-13.4 years). The median renal length z-scores of those without any renal dysfunction (n = 37, 25.1%) were greater (+3.66, interquartile range 3.02-4.47) than those with renal dysfunction (median 3.11, interquartile range 1.76-4.11, P = .0107, Mann-Whitney test). Using a cut-off of z-score of >+1.911, the odds ratio for having no renal dysfunction was 0.07 (95% CI 0.002-0.459, P = .0010). However, accuracy of the renal length z-score was poor (ROC curve 0.6488).

CONCLUSION

In this cohort of children with SKF, using the renal length z-score as a biomarker of renal dysfunction at 7 years of age is not recommended.

Mismatch between poor fetal growth and rapid postnatal weight gain in the first 2 years of life is associated with higher blood pressure and insulin resistance without increased adiposity in childhood: the GUSTO cohort study

BACKGROUND

Using longitudinal ultrasounds as an improved fetal growth marker, we aimed to investigate if fetal growth deceleration followed by rapid postnatal weight gain is associated with childhood cardiometabolic risk biomarkers in a contemporary well-nourished population.

METHODS

We defined fetal growth deceleration (FGD) as ultrasound-measured 2nd-3rd-trimester abdominal circumference decrease by ≥0.67 standard deviation score (SDS) and rapid postnatal weight gain (RPWG) as 0-2-year-old weight increase by ≥0.67 SDS. In the GUSTO mother-offspring cohort, we grouped 797 children into four groups of FGD-only (14.2%), RPWG-only (23.3%), both (mismatch, 10.7%) or neither (reference, 51.8%). Adjusting for confounders and comparing with the reference group, we tested associations of these growth groups with childhood cardiometabolic biomarkers: magnetic resonance imaging (MRI)-measured abdominal fat (n = 262), liver fat (n = 216), intramyocellular lipids (n = 227), quantitative magnetic resonance-measured overall body fat % (BF%) (n = 310), homeostasis model assessment of insulin resistance (HOMA-IR) (n = 323), arterial wall thickness (n = 422) and stiffness (n = 443), and blood pressure trajectories (ages 3-6 years).

RESULTS

Mean±SD birthweights were: FGD-only (3.11 ± 0.38 kg), RPWG-only (3.03 ± 0.37 kg), mismatch (2.87 ± 0.31 kg), reference (3.30 ± 0.36 kg). FGD-only children had elevated blood pressure trajectories without correspondingly increased BF%. RPWG-only children had altered body fat partitioning, higher BF% [BF = 4.26%, 95% confidence interval (CI) (2.34, 6.19)], HOMA-IR 0.28 units (0.11, 0.45)] and elevated blood pressure trajectories. Mismatch children did not have increased adiposity, but had elevated ectopic fat, elevated HOMA-IR [0.29 units (0.04,0.55)] and the highest blood pressure trajectories. Associations remained even after excluding small-for-gestational-age infants from analyses.

CONCLUSIONS

Fetal growth deceleration coupled with rapid postnatal weight gain was associated with elevated childhood cardiometabolic risk biomarkers without correspondingly increased BF%.

Nonalcoholic fatty liver disease and eGFR levels could be linked by the PNPLA3 I148M polymorphism in children with obesity

BACKGROUND

PNPLA3 I148M polymorphism has an effect on modulation of estimated glomerular filtration rate (eGFR) in nonobese nondiabetic adults and in children with histologically confirmed nonalcoholic fatty liver disease (NAFLD).

OBJECTIVES

The objective of the study is to explore the impact of PNPLA3 I148M polymorphism on eGFR in children with obesity with and without NAFLD.

METHODS

We genotyped 591 patients with obesity for PNPLA3 I148M polymorphism. Anthropometrical, biochemical, and instrumental data were collected. NAFLD was defined by the presence of ultrasound-detected liver steatosis and/or ALT levels greater than 40 IU/L.

RESULTS

Patients with NAFLD showed significantly lower eGFR levels compared with subjects without NAFLD. Children with PNPLA3 MM genotype showed lower eGFR levels compared with those with either PNPLA3 IM or II genotypes both in the presence and absence of NAFLD. A general linear model for eGFR variance, including gender, duration of obesity, PNPLA3 genotypes, HOMA, BMI-SDS, LDL-C, and triglycerides as covariates, confirmed an inverse association between eGFR and PNPLA3 genotype only in the presence of NAFLD.

CONCLUSIONS

Children with obesity and PNPLA3 MM genotype show lower eGFR levels compared with other genotypes, with a major effect of this polymorphism in the presence of NAFLD.

The effect of one year lifestyle intervention on eGFR in children and adolescents with overweight, obesity and morbid obesity

Obesity causes modifications in the kidneys reversed by weight loss in adults. There is little data on renal function and effects of weight loss in children with obesity. The aim of this prospective study was to examine renal function and effect of a lifestyle intervention in children with overweight, obesity and morbid obesity. Two hundred forty-five children (age 12.4 ± 3.3 years, 40% boys, BMI z-score 3.46 ± 0.70) participating in an out-patient lifestyle intervention were included. Children with at least 12 months follow-up (n = 144 (58.8%)) were included in the longitudinal study. Anthropometry, blood analysis and blood pressure measurements were performed at baseline and follow-up. Glomerular filtration rate (GFR) was estimated using the Schwartz and FAS equation. eGFR was de-indexed using body surface area. Different cut-off points for defining glomerular hyperfiltration were used for stratification. Depending on the definition and equation used, glomerular hyperfiltration was present in 2% to 18% of the participants. After intervention, de-indexed eGFR decreased significantly in children with baseline glomerular hyperfiltration, depending on the eGFR equation and definition for glomerular hyperfiltration used. No associations of changes in eGFR with changes in BMI z-score, blood pressure or parameters of glucose and lipid metabolism were found. In conclusion, after one year of lifestyle intervention, eGFR decreases in hyperfiltrating children and adolescents with overweight, obesity and morbid obesity. eGFR and changes over time in children with obesity depend on eGFR equation used and on de-indexing for body surface area.

Comorbidities in primary versus secondary school children with obesity and responsiveness to lifestyle intervention

CONTEXT

Childhood obesity increases the risk of diseases as diabetes, cardiovascular disease and non-alcoholic fatty liver disease.

OBJECTIVE

To evaluate the prevalence of comorbidities in school-age children with obesity and to compare its prevalence and the effect of a lifestyle intervention between children in primary and secondary school and between boys and girls.

DESIGN

Cross-sectional analysis and lifestyle intervention.

SETTING

Centre for Overweight Adolescent and Children's Healthcare.

PATIENTS

Comorbidities were evaluated in 149 primary and 150 secondary school children with (morbid) obesity (162 girls). The effect of lifestyle intervention was studied in 82 primary and 75 secondary school children.

INTERVENTION

One-year interdisciplinary lifestyle intervention.

RESULTS

Insulin resistance (37%), impaired glucose tolerance (IGT) (3%), dyslipidemia (48%), hypertension (7%) and elevated liver transaminase levels (54%) were already common in primary school children. Glomerular hyperfiltration and insulin resistance were more prevalent in secondary school children. IGT was more prevalent in girls.The change in BMI z-score after intervention was greater in primary school children (primary vs. secondary: -0.25±0.32 vs. -0.11±0.47), even as the change in LDL cholesterol concentrations (primary vs. secondary: -0.30(-0.70;0.10) vs. -0.10(-0.40;0.30)) and systolic blood pressure z-score (primary vs. secondary: -0.32±1.27 vs. 0.24±1.3). The change in BMI z-score, but not in comorbidities, was greater in boys (boys vs. girls: -0.33±0.45 vs. -0.05±0.31).

CONCLUSIONS

The presence of comorbidities is already evident in primary school children with obesity. The effect of a lifestyle intervention on these comorbidities is greater in primary compared to secondary school children, stressing the need for early interventions.

Educational review: measurement of GFR in special populations

IMPORTANCE

Changes in kidney function are typically followed by the sequential estimation of glomerular filtration rate (eGFR). Formulae for eGFR work well on a population basis, but there are well-known conditions where they do not work.

OBJECTIVE

The purpose of this review is to summarize the existing literature on special populations in the pediatric age range and provide recommendations on how to estimate GFR in these populations.

FINDINGS

The reliability of creatinine depends on muscle mass, while cystatin C (not widely available) is limited by inflammation and changes in protein catabolism. Various dietary factors can alter eGFR. Renal function in neonates changes drastically every day, and there are currently no satisfactory reference intervals for routine pediatric use. Gender effects and conditions such as wasting disease and obesity require alternative ways to obtain eGFR. In oncology patients, chemotherapy may negatively affect renal function, and nuclear GFR measurements may be necessary. For body builders, high muscle mass may lead to underestimation of eGFR using creatinine.

CONCLUSIONS AND RELEVANCE

Clinicians should be aware of special populations that may yield misleading eGFRs with conventional creatinine-based formulae, and that the alternative methods may be more appropriate for some populations.

Anthropometric and Biochemical Determinants of Estimated Glomerular Filtration Rate in a Large Cohort of Obese Children

OBJECTIVE

We aimed to investigate which clinical and metabolic factors could influence the estimated glomerular filtration rate (eGFR) levels, evaluating a large population of obese children without suspect of primary kidney disease.

DESIGN

Retrospective, cross-sectional study.

SETTING

Pediatric university department.

SUBJECTS

We enrolled 2,957 obese children and adolescents consecutively attending our department between January 2000 and 2017. Inclusion criteria were body mass index (BMI) > 95th percentile and eGFR > 90 mL/min/1.73 m2. Exclusion criteria were secondary forms of obesity, eGFR < 90 mL/min/1.73 m2, proteinuria/hematuria at urine dipstick, or consumption of any medication.

INTERVENTIONS

Weight, waist circumference, height, waist to height ratio (W/Hr), BMI-standard deviation score (SDS), pubertal stage, systolic blood pressure (SBP) and diastolic blood pressure (DBP), duration of obesity, insulin, eGFR, and homeostasis model assessment (HOMA-IR) were obtained. A general linear model was performed for a multiple variable analysis.

MAIN OUTCOME MEASURE

The population was divided in tertiles for BMI-SDS, W/Hr, SBP- and DBP-SDS, HOMA-IR, and duration of obesity. We compared eGFR levels among these tertiles.

RESULTS

The eGFR levels significantly increased across both BMI-SDS and W/Hr tertiles. Conversely the eGFR levels significantly decreased across SBP-SDS, HOMA-IR, and duration of obesity tertiles. No significant differences in eGFR levels across DBP-SDS tertiles were detected. Pubertal patients presented significantly lower eGFR values compared with prepubertal patients. A general linear model for eGFR variance including as covariates W/Hr, HOMA-IR, duration of obesity, pubertal stage, BMI-SDS, and SBP-SDS (model R2 39.7%; model P < .00001) was performed. It confirmed a direct association of eGFR values with BMI-SDS and an indirect association with HOMA-IR, duration of obesity, pubertal stage, and SBP-SDS.

CONCLUSIONS

We showed a positive correlation of eGFR with both BMI-SDS and a negative one with SBP-SDS, HOMA-IR, pubertal stage, and duration of obesity. The duration of obesity was the variable most significantly associated to eGFR levels.