Predicting isolated postchallenge hyperglycaemia: a new approach; Tehran Lipid and Glucose Study (TLGS)
Aims To determine factors predicting isolated postchallenge hyperglycaemia (IPH) defined as fasting plasma glucose (FPG) < 7.0 mmol/l and 2-h plasma glucose (2-hPG) >= 11.1 mmol/l after an oral glucose tolerance test (OGTT) and factors influencing the value of 2-hPG in a population-based study. Materials and methods From 15 005 participants in the Tehran Lipid and Glucose Study (TLGS), we analysed the results of OGTTs in 5386 individuals (2909 women and 2437 men) aged >= 20 years, free of known diabetes and any other disorders influencing glucose metabolism. Logistic and multiple linear regression models were developed to predict IPH and the 2-hPG, respectively. Results The overall prevalence of non-diabetic subjects, IPH and undiagnosed Type 2 diabetes mellitus (FPG >= 7.0 mmol/l) were 94.5% (n = 5088), 2.5% (n = 133) and 3.1% (n = 165), respectively. Of subjects with IPH, 29.3% (n = 39) had FPG levels < 5.6 mmol/l. Factors associated with IPH were FPG (mmol/l) [odds ratio (OR) 11.05, 95% confidence interval (CI) 7.9, 15.4], age >= 40 years (OR 2.0, 95% CI 1.3, 3.2), abnormal waist circumference (OR 2.1, 95% CI 1.4, 3.1) and serum triglycerides >= 1.7 mmol/l (OR 2.0, 95% CI 1.3, 3.1). In the multiple linear regression model, six explanatory factors (FPG, age, female sex, triglycerides, systolic blood pressure, waist circumference) were positively related to 2-hPG. The model could predict 47.7% of total variance of 2-hPG. Conclusions Based on our results in this Iranian population, OGTT can be recommended in subjects with FPG < 7.0 mmol/l in the presence of abnormal waist circumference and triglycerides, age >= 40 years and in particular when FPG is close to 7.0 mmol/l.