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.