Oral glucose tolerance test in children and adolescents: positives and pitfalls

Single Point Insulin Sensitivity Estimator (SPISE) As a Prognostic Marker for Emerging Dysglycemia in Children with Overweight or Obesity

The single point insulin sensitivity estimator (SPISE) is a recently developed fasting index for insulin sensitivity based on triglycerides, high density lipoprotein cholesterol, and body mass index. SPISE has been validated in juveniles and adults; still, its role during childhood remains unclear. To evaluate the age- and sex-specific distribution of SPISE, its correlation with established fasting indexes and its application as a prognostic marker for future dysglycemia during childhood and adolescence were assessed. We performed linear modeling and correlation analyses on a cross-sectional cohort of 2107 children and adolescents (age 5 to 18.4 years) with overweight or obesity. Furthermore, survival analyses were conducted upon a longitudinal cohort of 591 children with overweight/obesity (1712 observations) with a maximum follow-up time of nearly 20 years, targeting prediabetes/dysglycemia as the end point. The SPISE index decreased significantly with age (−0.34 units per year, p < 0.001) among children and adolescents with overweight and obesity. Sex did not have an influence on SPISE. There was a modest correlation between SPISE and established fasting markers of insulin resistance (R = −0.49 for HOMA-IR, R = −0.55 for QUICKI-IR). SPISE is a better prognostic marker for future dysglycemia (hazard ratio (HR) 3.47, 95% confidence interval (CI) 1.60−7.51, p < 0.01) than HOMA-IR and QUICKI-IR (HR 2.44, 95% CI 1.24−4.81, p < 0.05). The SPISE index is a surrogate marker for insulin resistance predicting emerging dysglycemia in children with overweight or obesity, and could, therefore, be applied to pediatric cohorts that lack direct insulin assessment.

High predictability of impaired glucose tolerance by combining cardiometabolic screening parameters in obese children

BACKGROUND

There is debate on which overweight and obese children should be screened for the presence of impaired glucose tolerance (IGT) by oral glucose tolerance testing (OGTT). The objective of the study was to identify risk factors predictive of the presence of IGT.

METHODS

In a cohort of overweight children, who underwent OGTT, we determined the association of anthropometric and laboratory parameters with IGT and whether combining parameters improved the sensitivity of screening for IGT.

RESULTS

Out of 145 patients, IGT was present in 11, of whom two had impaired fasting glucose (IFG). Elevated blood pressure (p=0.025) and elevated liver enzymes (p=0.003) were associated with IGT, whereas IFG was not (p=0.067), screening patients with either one of these parameters predicted IGT with a high sensitivity of 1.00, and a number needed to screen of 5.7.

CONCLUSIONS

Screening all patients with either IFG, presence of elevated blood pressure and elevated liver enzymes, significantly increases predictability of IGT compared to using IFG alone.

Triglycerides-to-HDL cholesterol ratio as screening tool for impaired glucose tolerance in obese children and adolescents

AIMS

To identify metabolic phenotypes at increased risk of impaired glucose tolerance (IGT) in Italian overweight/obese children (n = 148, age 5-10 years) and adolescents (n = 531, age 10-17.9 year).

METHODS

Phenotypes were defined as follows: obesity by the 95th cut-points of the Center for Disease Control body mass index reference standards, impaired fasting glucose (fasting plasma glucose ≥100 mg/dl), high circulating triglycerides (TG), TG/HDL cholesterol ≥2.2, waist-to-height ratio (WTHR) >0.6, and combination of the latter with high TG or TG/HDL cholesterol ≥2.2.

RESULTS

In the 148 obese children, TG/HDL-C ≥ 2.2 (OR 20.19; 95 % CI 2.50-163.28, p = 0.005) and the combination of TG/HDL-C ≥ 2.2 and WTHR > 0.60 (OR 14.97; 95 % CI 2.18-102.76, p = 0.006) were significantly associated with IGT. In the 531 adolescents, TG/HDL-C ≥ 2.2 (OR 1.991; 95 % CI 1.243-3.191, p = 0.004) and the combination with WTHR > 0.60 (OR 2.24; 95 % CI 1.29-3.87, p = 0.004) were associated with significantly increased risk of IGT. In the whole sample, having high TG levels according to the NIH National Heart, Lung and Blood Institute Expert Panel was not associated with an increased risk of presenting IGT.

CONCLUSIONS

TG/HDL-C ratio can be useful, particularly in children, to identify obese young patients at risk of IGT. Its accuracy as screening tool in a general population needs to be verified. The combination of TG/HDL-C ratio and WTHR > 0.6 did not improve prediction. Having high TG according to the NIH definition was not associated with increased risk of developing IGT.

How to screen obese children at risk for type 2 diabetes mellitus?

BACKGROUND

Recommended screening to identify children at risk for diabetes and its precursors impaired glucose tolerance (IGT) and insulin resistance (IR) is fasted plasma glucose (FPG). This study evaluates the added value of fasted plasma insulin (FPI).

METHODS

This study analyzed routinely collected data of an oral glucose tolerance test (OGTT) of 311 obese children (age 10.8 ± 3.2 years). Diabetes and IGT were defined according to the American Diabetes Association criteria, IR as homeostasis model assessment (HOMA)-IR ≥3.4.

RESULTS

Cases diagnosed with an OGTT if FPG ≥5.6 mmol/L, compared with an OGTT performed if FPG ≥5.6 mmol/L or HOMA-IR ≥3.4, were, respectively, 4 (80%) versus 5 (100%) with diabetes, 7 (28%) versus 16 (64%) with IGT, and 0 (0%) versus 93 (100%) with IR.

CONCLUSIONS

Screening with FPG and FPI has equal burden compared with screening with FPG alone, identifies all patients with diabetes, and identifies more patients with precursors of diabetes.

Reproducibility of the oral glucose tolerance test in overweight children

OBJECTIVE

We examined the reproducibility of the oral glucose tolerance test (OGTT) in overweight children and evaluated distinguishing characteristics between those with concordant vs. discordant results.

DESIGN

Sixty overweight youth (8-17 yr old) completed two OGTTs (interval between tests 1-25 d). Insulin sensitivity was assessed by the surrogate measures of fasting glucose to insulin ratio, whole-body insulin sensitivity index, and homeostasis model assessment of insulin resistance, and insulin secretion by the insulinogenic index with calculation of the glucose disposition index (GDI).

RESULTS

Of the 10 subjects with impaired glucose tolerance (IGT) during the first OGTT only three (30%) had IGT during the second OGTT. The percent positive agreement between the first and second OGTT was low for both impaired fasting glucose and IGT (22.2 and 27.3%, respectively). Fasting blood glucose had higher reproducibility, compared with the 2-h glucose. Youth with discordant OGTTs, compared with those with concordant results, were more insulin resistant (glucose/insulin 2.7+/-1.4 vs. 4.1+/-1.8, P=0.006, whole-body insulin sensitivity index of 1.3+/-0.6 vs. 2.2+/-1.1, P=0.003, and homeostasis model assessment of insulin resistance 10.6+/-8.1 vs. 5.7+/-2.8, P=0.001), had a lower GDI (0.45+/-0.58 vs. 1.02+/-1.0, P=0.03), and had higher low-density lipoprotein cholesterol (117.7+/-36.6 vs. 89.9+/-20.1, P=0.0005) without differences in physical characteristics.

CONCLUSIONS

Our results show poor reproducibility of the OGTT in obese youth, in particular for the 2-h plasma glucose. Obese youth who have discordant OGTT results are more insulin resistant with higher risk of developing type 2 diabetes mellitus, as evidenced by a lower GDI. The implications of this remain to be determined in clinical and research settings.

Prevalence of metabolic syndrome in obese Turkish children and adolescents

OBJECTIVE

The aim of our study was to assess the prevalence of metabolic syndrome and the other metabolic features in obese children.

METHODS

We have studied 169 obese children and adolescents (body mass index>95th percentile), 100 prepubertal and 69 pubertal, aged between 7 and 18 years. Each subject was submitted to an oral glucose tolerance test. The diagnosis of impaired glucose tolerance, type 2 diabetes and metabolic syndrome were defined according to modified WHO criteria adapted for children.

RESULTS

Metabolic syndrome was found in 27.2%, with a significantly higher rate among adolescents aged 12-18 years (37.6%) than among children aged 7-11 years (20%) (p < 0.001). There were no significant differences in the prevalence of metabolic syndrome by sex. The prevalences of insulin resistance, glucose intolerance and type 2 diabetes were 29, 19 and 2% among prepubertal children and 56.5, 27.5 and 4.3% among pubertal group, respectively. The prevalence of fasting hyperinsulinemia in pubertal group was significantly higher than prepubertal children (p < 0.001). Hyperinsulinemia was also more frequent in pubertal children with significant difference (20% versus 43.7%, p < 0.001). Hypertension was significantly more common in adolescents (31.8%) than children (15%) with obesity, as expected (p < 0.013). Overall, dyslipidaemia in prepubertal and pubertal groups was identified in 42 and 55%, respectively, with no significant differences (p = 0.085).

CONCLUSIONS

Type 2 diabetes mellitus and metabolic syndrome prevalences among adolescents are quite high in the urban area of Konya, central Anatolia, with abnormal lipid profiles, obesity and nutritional mistakes.