Comparison of the Clinical Utility of Two Insulin Resistance Indices: IRI-HOMA and IRI-Belfiore in Diagnosing Insulin Resistance and Metabolic Complications in Children Based on the Results Obtained for the Polish Population

Background: Recognizing insulin resistance (IR) in children remains challenging due to uncertain IRI-HOMA cut-offs and unclear recommendations for evaluating IR based on OGTT. In our study, we compare the effectiveness of IRI-HOMA and IRI-Belfiore (OGTT-based) in detecting IR and its metabolic complications in children. Methods: The analysis included 553 children who were hospitalized at the Department of Endocrinology and Metabolic Diseases of the Polish Mother's Memorial Hospital Research Institute (PMMH-RI) in Lodz, Poland, between 2002 and 2018 due to various reasons-of these, 67.5% were girls. All underwent OGTT for glucose and insulin assessment. IR diagnosis relied on IRI-HOMA and IRI-Belfiore. IR based on IRI-HOMA was evaluated using three criteria: (A) >2.5; (B) >2.67 in boys and >2.22 in girls before puberty and >5.22 and >3.82 during puberty, respectively; (C) >95th percentile according to charts for IRI-HOMA in children. Results: Prepubertal children exhibited significantly lower IRI-HOMA and IRI-Belfiore than their pubertal counterparts (p < 0.00005). IRI-HOMA and IRI-Belfiore values positively correlated with age and BMI SDS value (p < 0.000001 for all calculations). As many as 26% to 46.9% of children with normal IRI-HOMA showed elevated IRI-Belfiore, with notably higher levels of triglycerides, a lower HDL cholesterol fraction, and a lower HDL/total cholesterol ratio in this subgroup. Conclusions: A notable proportion of children exhibited elevated IRI-Belfiore levels despite having normal IRI-HOMA values. This suggests the possibility of peripheral IR preceding hepatic IR in children-omitting an OGTT may therefore lead to overlooking cases of IR. Children diagnosed with IR via OGTT displayed significantly poorer lipid profiles compared to those without IR (characterized by normal values in both IRI-HOMA and IRI-Belfiore). This underscores the ability of OGTT-derived IR indices to identify individuals at risk of developing complications associated with obesity and IR before the onset of metabolic syndrome (MS) symptoms. If IR is already detected in children based on fasting glucose and insulin levels (IRI-HOMA), further evaluation may not be warranted, as OGTT results often simply confirm the diagnosis.