Evaluation of Postprandial To Fasting Insulin Ratio as a Biochemical Marker of Insulin Resistance in Obese Indian Children

Abstract

Background:Insulin resistance in childhood obesity is a well recognised and worrisome complication. Reliable measurements of insulin resistance require invasive or multiple sampling procedures or complex mathematical calculations which are difficult to practice in routine office practice. Objective:This observational study was aimed to evaluate a simple ratio of 120 minute post glucose load (OGTT) insulin to fasting insulin for diagnosis of insulin resistance in obese children having clinical markers of insulin resistance and with a HOMA-IR value suggestive of insulin resistance for age and sex. Methods:Forty Eight obese children and adolescents (35 girls and 34 boys; mean age 10.19 ± 4.23 years and mean BMI 26.17± 3.76) were included in the study. All participants underwent an OGTT. Blood samples were obtained 0 and 120 minutes after oral glucose administration for glucose and insulin measurements, and 2 separate groups were studied in both pubertal and pre-pubertal age group, according to the presence or absence of insulin resistance as per the standard HOMA-IR cut-offs. The ratio of 120 minute and fasting insulin, measurements was termed as insulin resistance Index (Ri) and was calculated for both pre-pubertal and pubertal children with insulin resistance. The accuracy of this measurement in measuring Insulin Resistance and the optimal insulin resistance index (Ri) for diagnosis of insulin resistance was established with a receiver operating characteristic (ROC) curve. Results:The area under the curve for pre-pubertal children was 0.7(close to upper left) and yielded a sensitivity of 76% and specificity of 70% at Ri value of 4.7. The value of positive likelihood ratio comes at 2.53, pretest probability of 0.61, pretest odds of 1.56, post-test odds of 3.95 and post-test probability of 0.78. However ROC plot had area under the curve of only 0.3 in pubertal children (close to bottom right). Conclusion:Ri is a sensitive and specific test for calculation of insulin resistance in pre pubertal children but not accurate in pubertal children.