Population-specific HOMA-IR reference ranges in Iraq: Defining insulin sensitivity in a Middle Eastern cohort

The homeostatic model assessment for insulin resistance (HOMA-IR) is one of the most commonly applied surrogate markers for the measurement of insulin resistance; however, the use of this metric does require sex-specific, age-specific, and body mass index (BMI)-specific reference ranges due to variations among populations and there is a lack of data in countries like Iraq on such reference ranges. The purpose of this investigation was to develop sex-, age-, and BMI-specific reference ranges for HOMA-IR in apparently healthy Iraqi adults aged 18 to 60 years. There were 2,160 participants enrolled in the study who were equally divided into sex-specific groups and age groups (18-30, 31-45, and 46-60 years) and BMI categories (normal weight, overweight, and obesity). In addition to measuring fasting glucose and insulin levels, the HOMA-IR was calculated. Reference ranges, which included the 2.5th and 97.5th percentiles of HOMA-IR, were developed using non-parametric statistical methods based on CLSI EP28-A3c guidelines. The results demonstrated that HOMA-IR values increased as both age and BMI increased (p < 0.001). Also, males consistently had higher HOMA-IR values compared to females within similar subgroups. All between-group comparisons were statistically significant. It is important to use sex-, age-, and BMI-specific reference intervals when interpreting HOMA-IR to avoid misclassifying subjects in clinical and epidemiologic studies. This investigation represents the first large-scale study to identify such reference intervals in Iraq and adds relevant regional data to the global research on the prevalence of insulin resistance.