Endocrine Abstracts

Introduction: The incidence of Type 2 Diabetes Mellitus (T2DM) is rapidly increasing within the paediatric community, prompting searches for a simple and effective screening tool. Oral glucose tolerance test (OGTT) is the gold standard but is poorly accessible in the community. HbA1c offers an alternative which can be easily performed, but cut-offs for children have been extrapolated directly from the adult American Diabetes Association (ADA) diagnostic criteria. There is limited data for the accuracy of HbA1c as a screening tool in the paediatric population.

Aim: To assess the accuracy and utility of HbA1c as a DM screening tool against the gold standard (OGTT) in the paediatric population.

Method: Over five years, 70 patients undergoing OGTT at our hospital were found to have diabetes or pre-diabetes; 46 also had concurrent HbA1c tested. OGTT results classed as impaired fasting glucose (IFG, fasting plasma glucose ≥6.1 and <7 mmol/L), impaired glucose tolerance (IGT, 2hour plasma glucose ≥7.8 and <11.1 mmol/L) and diabetes mellitus (FPG ≥ 7 mmol/L or 2hPG ≥11.1) were compared with HbA1c categories as per ADA criteria.

Results: As can be seen in the table, there was no difference in HbA1c results between IFG, IGT and DM (defined by OGTT) groups (chi square = 3.94, P=0.41). The sensitivity of HbA1c for detection of DM was only 23%, with a specificity of <77%. Sensitivity of HbA1c for IFG and IGT was similarly low, at 48%.

Conclusions: Our results demonstrate that ADA HbA1c cutoffs are insufficiently sensitive to identify those with pre-diabetes and T2DM in adolescent patients. It is likely that at the point of abnormal HbA1C detection in children, beta-cell reserve may be more significantly compromised with later detection of glycaemic dysfunction. OGTT must remain the screening test of choice for all paediatric patients at risk of dysglycaemia. Further analysis is required to determine accuracy of HbA1C thresholds specific to the UK paediatric population with more subtle glycaemic problems.