HbA_1c values for defining diabetes and impaired fasting glucose in Asian Indians

Aim: To determine the glycosylated haemoglobin (HbA_1c) cut-points for diabetes and impaired fasting glucose (IFG) among Asian Indians. Methods: Participants (n = 525) were a random sample selected from the India Health Study. Based on history and fasting plasma glucose (FPG), participants were classified into known diabetes, newly diagnosed diabetes (NDD), impaired fasting glucose (IFG) [ADA and WHO criteria] or normal fasting glucose (NFG). Receiver Operating Characteristic curves were used to identify the optimum sensitivity and specificity for defining HbA_1c cut-points for NDD and IFG against the FPG criteria. Results: There were 64 participants with a known history of diabetes. Of the remaining 461, IFG was present in 44.7% (ADA) and 18.2% (WHO), and 10.4% were NDD. Mean HbA_1c were 5.4 (±0.04)% for NFG; 5.7 (±0.06)% among IFG-ADA, 5.8 (±0.09)% among IFG-WHO; 7.5 (±0.33)% for NDD and 8.4 (±0.32)% for known diabetes. Optimal HbA_1c cut-point for NDD was 5.8% (sensitivity = 75%, specificity = 75.5%, AUC = 0.819). Cut-point for IFG (ADA) was 5.5% (sensitivity = 59.7%, specificity = 59.9%, AUC = 0.628) and for IFG (WHO) was 5.6% (sensitivity = 60.7%, specificity = 65.1%, AUC = 0.671). Conclusion: In this study population from north and south regions of India, the HbA_1c cut-point that defines NDD (≥5.8%) was much lower than that proposed by an international expert committee and the American Diabetes Association (≥6.5%). A cut-point of ≥5.5% or ≥5.6% defined IFG, and was slightly lower than the ≥5.7% for high risk proposed, but accuracy was less than 70%.