Glycated haemoglobin as a screening test for abnormal glucose homeostasis in childhood obesity

Abstract

To estimate the proportion of type 2 diabetes mellitus and abnormal glucose homeostasis in childhood obesity and assess the predictive role of HbA1c as a diagnostic marker compared with oral glucose tolerance testing (OGTT). A retrospective study in a tertiary paediatric hospital. Data were collected on all overweight or obese children who underwent routine OGTT between 2012 and 2016. Ethnicity, anthropometry, comorbidities and other risk factors associated with diabetes were recorded systematically. Fasting venous glucose, insulin and HbA1c values, along with 120-min venous glucose were recorded. Receiver operating characteristic (ROC) curve analysis was performed to derive optimum thresholds of HbA1c for detection of type 2 diabetes, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT). Predictive HbA1c thresholds forthe detection of abnormal glucose homeostasis in children with obesity were calculated. Of 156 children, 13 (8%, 10 female, 10 Asian) had type 2 diabetes, 95 (61%) had normal glucose tolerance, 18 (12%) had isolated IFG, 19 (12%) had isolated IGT, and another 11 (7%) had both IFG and IGT. The proportion of abnormal glucose homeostasis was 39%. ROC curve analysis demonstrated that HbA1c ≥42mmol/mol (6.0%) predicted type 2 diabetes (specificity 95%, sensitivity 85%) but performed moderately for IFG (specificity 46%, sensitivity 78%) and IGT (specificity 78%, sensitivity 55%). Despite HbA1c being a less-sensitive diagnostic tool compared with OGTT for children with IFG and IGT, it is reliable in detecting type 2 diabetes in asymptomatic children with obesity, instead of the labour- and cost-intensive OGTT.