OGTT and random plasma glucose in the prediction of type 1 diabetes and time to diagnosis.

Aims/hypothesis: We assessed the utility of the OGTT and random plasma glucose concentrations in predicting the time to diagnosis of type 1 diabetes.

Methods: A population-derived cohort of 14,876 newborns with HLA-conferred risk of type 1 diabetes were invited to regular follow-up for islet autoantibodies. When two or more autoantibodies were detected, an OGTT was performed once a year and random plasma glucose analysed twice a year. During follow-up, 567 children developed multiple autoantibodies, 255 (45%) of whom were diagnosed with type 1 diabetes, while 312 remained non-diabetic by December 2011.

Results: Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) were risk factors for type 1 diabetes (HR 3.2 [95% CI 1.5, 7.0] and 8.3 [95% CI 6.0, 11.5], respectively). When a random plasma glucose value ≥ 7.8 mmol/l was observed, the HR for diabetes was 6.0 (95% CI 4.3, 8.6). The median time to diagnosis after the detection of IFG was 5.2 years (interquartile range [IQR] 3.4, 6.3); after IGT, 0.7 years (IQR 0.3, 1.9); and, after a random plasma glucose ≥ 7.8 mmol/l, 1.0 years (IQR 0.3, 1.5). In a retrospective analysis, both OGTT-derived 2 h plasma glucose and random plasma glucose started to increase 1.5 years before diagnosis (p < 0.001 and p = 0.004, respectively).

Conclusions/interpretation: Dysglycaemia detected in an OGTT or based on random plasma glucose is a useful marker in the prediction of time to onset of type 1 diabetes in high-risk children. Random plasma glucose is a simple and low-cost measurement with comparable predictive characteristics to that of OGTT-derived 2 h glucose.