Continuous glucose monitoring and HbA1c in the evaluation of glucose metabolism in children at high risk for type 1 diabetes mellitus

•High-risk children show increased glycemic variation in CGM compared to controls.•Increased time spent ⩾7.8 mmol/l in CGM is a characteristic feature among autoantibody-positive children.•Increased evening glucose levels are present in high-risk children.•Glucose measured by CGM and SMBG are useful indicators of dysglycemia.

AimsContinuous glucose monitoring (CGM) parameters, self-monitored blood glucose (SMBG), HbA1c and oral glucose tolerance test (OGTT) were studied during preclinical type 1 diabetes mellitus.MethodsTen asymptomatic children with multiple (⩾2) islet autoantibodies (cases) and 10 age and sex-matched autoantibody-negative controls from the Type 1 Diabetes Prediction and Prevention (DIPP) Study were invited to 7-day CGM with Dexcom G4 Platinum Sensor. HbA1c and two daily SMBG values (morning and evening) were analyzed. Five-point OGTTs were performed and carbohydrate intake was assessed by food records. The matched pairs were compared with the paired sample t-test.ResultsThe cases showed higher mean values and higher variation in glucose levels during CGM compared to the controls. The time spent ⩾7.8 mmol/l was 5.8% in the cases compared to 0.4% in the controls (p = 0.040). Postprandial CGM values were similar except after the dinner (6.6 mmol/l in cases vs. 6.1 mmol/l in controls; p = 0.023). When analyzing the SMBG values higher mean level, higher evening levels, as well as higher variation were observed in the cases when compared to the controls. HbA1c was significantly higher in the cases [5.7% (39 mmol/mol) vs. 5.3% (34 mmol/mol); p = 0.045]. No differences were observed in glucose or C-peptide levels during OGTT. Daily carbohydrate intake was slightly higher in the cases (254.2 g vs. 217.7 g; p = 0.034).ConclusionsGlucose levels measured by CGM and SMBG are useful indicators of dysglycemia during preclinical type 1 diabetes mellitus. Increased evening glucose values seem to be common in children with preclinical type 1 diabetes mellitus.