The potential impact and optimal cut-points of using glycated haemoglobin, HbA1c, to detect people with impaired glucose regulation in a UK multi-ethnic cohort

Introduction Recommended diagnostic cut-points to detect impaired glucose regulation (IGR, also termed prediabetes impaired fasting glucose and/or impaired glucose tolerance based on WHO 1999 criteria) are HbA1c 6 0-6 4% and 5 7-6 4% from an International Expert Committee and American Diabetes Association, respectively We investigated the impact on prevalence/phenotype from using these criteria compared to IGR detected on oral glucose tolerance testing (OGTT) and determined optimal HbA1c cut-points for IGR in a multi-ethnic cohort Methods Analysis of 8696 participants in the LEADER study of primary care individuals aged 40-75 years without diabetes, in Leicestershire (UK) who underwent OGTT and had HbA1c measured Results Use of OGTT detected less people with IGR (n = 1407, 16 2%) compared to HbA1c 6 06 4% (n = 1610, 18 5%) and HbA1c 5 7-6 4%(n = 3904, 44.9%), a 1 1- and 2 8-fold increase in prevalence, respectively There were 930 (10 7%) and 534 (6 1%) people with IGR on OGTT not detected using HbA1c 6 0-6 4% and 5 7-6 4%, respectively From ROC curve analysis, the optimal cut-point for detecting IGR in white Europeans was HbA1c >= 5 8%, sensitivity/specificity 61 5%/67.9%, but in south Asians HbA1c >= 6 0%, sensitivity/specificity 63 8%/69 4% Conclusion Recommended HbA1c cut-points to detect IGR significantly increase numbers detected, however introduce a change in people identified Using HbA1c 6 0-6 4% lacks sensitivity in white Europeans, but is a reasonable option in south Asians (C) 2010 Elsevier Ireland Ltd All rights reserved