20/ (fasting C-peptide × fasting plasma glucose) as a novel marker for insulin resistance in obese children and adolescents

BACKGROUND: Insulin resistance (IR) constitutes a critical pathophysiological mechanism linking pediatric obesity to type 2 diabetes mellitus (T2DM) and cardiovascular disease. Recent investigations in adult populations have proposed 20/ fasting C-peptide × fasting plasma glucose (20/ (Fcpep X FBG)) as a good biomarker for IR. We aimed to evaluate the diagnostic utility of this novel index in detecting IR among obese pediatric patients. METHODS: This case-control study included 100 children (50 obese and 50 controls), aged 6-16 years. Anthropometric, clinical, and laboratory assessments were performed, including fasting blood glucose, fasting serum insulin, fasting C-peptide, and lipid profile. IR was evaluated using HOMA-IR, HbA1c, TyG index, and 20/ (Fcpep X FBG). RESULTS: Obese children demonstrated significantly elevated metabolic parameters, including body mass index (BMI), HOMA-IR, and fasting C-peptide. The (20/Fcpep x FBG) index was significantly lower in obese subjects (0.10 ± 0.04 vs. 0.18 ± 0.05, p < 0.001) and exhibited strong inverse correlations with HOMA-IR, BMI, TyG index, and HbA1c. 20/ Fcpep X FBG can significantly predict IR at a cut-off ≤0.164 with 86.67% sensitivity, 85% specificity. CONCLUSIONS: The 20/ (Fcpep X FBG) index represents a convenient and accurate biomarker for IR detection in obese pediatric populations, demonstrating robust correlations with established metabolic indicators. IMPACT: Insulin resistance (IR) constitutes a critical pathophysiological mechanism linking pediatric obesity to type 2 diabetes mellitus (T2DM) and cardiovascular disease. Homeostatic model assessment of insulin resistance (HOMA-IR) and Triglyceride glucose (TyG) index serve as the established surrogate markers; recent investigations in adult populations have proposed 20/ fasting C-peptide × fasting plasma glucose (20/ (Fcpep X FBG) as a superior alternative. However, its utility in pediatric patients with obesity has not been evaluated. We found that the (20/ (Fcpep X FBG) is a promising and reliable marker for detecting IR in obese children and adolescents.