Optimal cut-offs of homeostasis model assessment of insulin resistance to identify dysglycaemia and diabetes

OBJECTIVE: The homeostasis model assessment of insulin resistance (HOMA-IR) has been used extensively as an index of insulin resistance in clinical research. However, the normal reference value in Chinese has not been defined. This study aimed to establish HOMA-IR cut-offs for identifying dysglycaemia and type 2 diabetes mellitus (T2DM) in Southern Chinese, based on the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS), a population-based cohort study with long-term follow-up. METHODS: Data were analysed from 2779 Hong Kong Chinese subjects aged 25 to 74 years from CRISPS 1 (1995- 1996) as baseline and followed up in CRISPS 4 (2010-2012). Normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and T2DM were defined according to the 1998 World Health Organization criteria. In our study, dysglycaemia referred to IFG, IGT, or T2DM. Super-control was defined as subjects who were NGT both at baseline and at CRISPS 4 (n=872). The optimal HOMA-IR cut-offs for dysglycaemia and T2DM were determined by the Youden index on the receiver operating characteristic (ROC) curve. Their sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) were also calculated. RESULTS: The optimal HOMA-IR cut-offs to identify dysglycaemia and T2DM at baseline were 1.37 (area under the ROC [AUC]=0.735; 95% confidence interval [CI], 0.713-0.758; Se, 65.6%; Sp, 71.3%; PPV, 44.9%; NPV, 85.4%) and 1.97 (AUC=0.807; 95% CI, 0.777-0.886; Se, 65.5%; Sp, 82.9%; PPV, 29.8%; NPV, 95.6%), respectively. These cutoffs corresponded closely to the 75th (1.44) and 90th (2.03) percentiles, respectively, of HOMA-IR in the supercontrols. CONCLUSION: HOMA-IR cut-offs, derived from this long-term follow-up study, of 1.4 and 2.0 discriminated dysglycaemia and T2DM respectively from NGT in Southern Chinese. These cut-off values can serve as useful references in clinical research involving the assessment of insulin resistance