Incidence of hyperglycaemic disorders in children and adolescents with obesity

Introduction
The prevalence of obesity in the paediatric population has increased significantly in recent decades. To date, the rarest metabolic disturbance associated with obesity has been the hyperglycaemia, including diabetes. The aim of the study was to compare the prevalence of hyperglycaemic disorders diagnosed on the basis of (1) the oral glucose tolerance test (OGTT) and (2) the HbA1c value, and to estimate the prevalence of hyperglycaemia in continuous glucose monitoring (CGM) records in adolescents with obesity.

Material and methods
The study included patients aged 9–18 years with obesity (BMI ≥ 95th percentile). The height, body weight, and waist circumference were measured, and the BMI and BMI Z-score were calculated. Sexual maturity was assessed on the Tanner scale. OGTT was performed, and the HbA1c value was measured. Six-day retrospective blinded CGM was performed.

Results
In the group of 143 children (mean age 13.4 years), the severity of obesity positively increased with patients age (r = 0.36 and p < 0.0001). Abdominal obesity was found in 93.4% of children. Based on OGTT, 18.8% of the subjects had hyperglycaemic disorders; impaired glucose tolerance was the most common one (16.1%). Impaired fasting glucose was found in 4 patients (2.8%), and type 2 diabetes was found in 2. The mean HbA1c was 5.4%. HbA1c values ranged from 5.7 to 6.4% in 20.3% of the patients, and it did not exceed 6.4% in any patient. In 27.6% of patients with HbA1c 5.7–6.4%, abnormalities in OGTT were observed (IGT 17.25%, IFG 6.9%, DM2 3.45%). There was a significant discrepancy between OGTT results and HbA1c in the diagnosis of hyperglycaemic disorders (diagnosis agreement – 69.92%). In CGM 1.4% of results were above 140 mg/dl.

Conclusions
Hyperglycaemic disorders are diagnosed in nearly 20% of children with obesity. However, there are significant discrepancies in the diagnosis of glucose disturbances using OGTT and HbA1c. Concordance in the diagnosis of hyperglycaemic disorders was achieved only in 70% of patients. CGM may be useful in the diagnosis of pre-diabetes in people with obesity.