Role of Matsuda Index in Identifying Patients at Risk for Cystic Fibrosis-Related Diabetes Development

Background: Cystic fibrosis-related diabetes (CFRD) is a frequent comorbidity in individuals with cystic fibrosis (CF). While insulin secretion defects are the primary mechanism in CFRD pathophysiology, insulin resistance may contribute as an additional risk factor. Early detection of insulin resistance may help identify patients at higher risk for earlier CFRD development. Objective: The aim of this study was to evaluate the ability of the Matsuda Index to identify insulin resistance in pediatric CF patients and to compare it with HOMA-IR as complementary indicators of glucose metabolism. Methods: In this cross-sectional study, fifty children with CF aged 6-16 years were included. The study involved measuring anthropometric data, fasting insulin, fasting glucose levels, glycated hemoglobin (HbA1c), and C-peptide. An assessment of glucose and insulin levels was performed on the patients through an oral glucose tolerance test (OGTT) at 0, 60, and 120 min. The Matsuda Index was computed, wherein a threshold of ≤4.5 signifies the presence of insulin resistance. Statistical analyses were conducted to compare insulin resistance and sensitivity across groups, using t-tests, correlation, and ANOVA. Results: Among the 50 observed patients, the average Matsuda index score was 17.08 with a standard deviation of 11.16. Eleven individuals (22%) exhibited insulin resistance with a Matsuda Index ≤ 4.5. These patients showed significantly higher insulin levels at 60 and 120 min during the OGTT, with statistically significant p-values of 0.008 and 0.002, respectively. Conclusions: The Matsuda Index may serve as a useful adjunctive tool to help identify insulin resistance in pediatric CF patients, particularly during puberty. Early detection of insulin resistance through the Matsuda Index may facilitate risk stratification and enable timely interventions that could potentially delay the onset or progression of CFRD. However, it should be noted that the ≤4.5 cut-off value was derived from adult studies, and its validity in pediatric CF populations has not been established, which represents a limitation of our finding.