OGTT testing in paediatric obesity: can fasting glucose and HbA1c guide us?

Cullingford David J; Munibah Bashir; Blair Joanne C; Senthil Senniappan

doi:10.1530/endoabs.111.P147

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Endocrine Abstracts (2025) 111 P147 | DOI: 10.1530/endoabs.111.P147

BSPED2025 Poster Presentations Obesity 2 (7 abstracts)

OGTT testing in paediatric obesity: can fasting glucose and HbA1c guide us?

David J Cullingford ^1,2 , Munibah Bashir ¹ , Joanne C Blair ^1,3 & Senthil Senniappan ¹

Author affiliations

¹Department of Endocrinology, Alder Hey Children’s Hospital, Liverpool, United Kingdom; ²University of Western Australia, Perth, Australia; ³Honorary Professor, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom

Objective: Whilst oral glucose tolerance tests (OGTT) are routinely used to assess for diabetes mellitus and impaired glucose tolerance (IGT) in paediatric obesity, they are costly, time consuming, can be unpleasant and have poor reproducibility. Some studies have suggested lower fasting plasma glucose (FPG) and HbA1c thresholds for predicting diabetes/IGT risk. We assessed the FPG and HbA1c thresholds with the greatest sensitivity for detecting IGT on OGTT.

Method: Retrospective analysis of children undergoing OGTT at a single paediatric tertiary institution from 2020-2025. Patient age, body mass index (BMI) standard deviation score (SDS), ethnicity, FPG, 2-hour glucose and HbA1c were recorded. IGT was defined as 7.8-11 mmol/l and hyperglycaemia as ≥11.1 mmol/l. Incremental changes in FPG and HbA1c cut-offs for screening were assessed for corresponding sensitivity and specificity for detecting an abnormal OGTT result.

Results: OGTT’s from 307 patients, (150 female, mean age 12.9 +/- 3.2 years) were paired with HbA1c, with 11.2% having IGT or hyperglycaemia. In participants under 10-years-old, 1/56 had hyperglycaemia, with an HbA1c of 54 mmol/mol (diabetes range). For those over 10-years-old, the highest sensitivity threshold was HbA1c ≥35 mmol/mol or FPG ≥5 mmol/l, giving 100% sensitivity (specificity 35.6%) for those aged 10-13 years, and 84.2% sensitivity (specificity 40%) ≥14 years. All cases of hyperglycaemia, and all but 3 cases of IGT screened positive (Table 1). BMI SDS and ethnicity were not significantly different between those with and without IGT.

Table 1: OGTT results
		Negative screen			Positive screen
	Normal	IGT	Hyper-glycaemia	Normal	IGT	Hyper-glycaemia	p
≥10 years (n = 251)	83	3	0	136	22	7	<0.001
10-13 years (n = 117)	37	0	0	67	10	3	0.009
≥14 years (n = 134)	46	3	0	69	12	4	0.042
P-value reflects difference in frequency of abnormal OGTT based on positive or negative screens (chi-square analysis).

Conclusion: Routine screening with OGTT has a low yield in those under 10-years-old. IGT is uncommon in those without FPG <5 mmol and HbA1c <35 mmol/mol, particularly in those under 14-years-old. Reserving OGTT for those with FPG/HbA1c above these thresholds or strong clinical suspicion of diabetes could be considered, reducing testing by approximately one third. Prospective studies to validate these thresholds are recommended.