Identifying central obesity as determinant of regression-to-normoglycaemia in patients with impaired fasting glucose

Abstract

Background: Fasting plasma glucose (FPG) is the most popular screening test for diabetes mellitus (DM) in Hong Kong primary care setting. Individuals with impaired fasting glucose (IFG) are commonly encountered. Objectives: To explore the determinants of regression-to-normoglycaemia among primary care patients with IFG based on non-invasive variables, and to establish a nomogram for the prediction of regression from IFG. Methods: This cohort study consisted of 1,197 primary care patients with confirmed IFG status. These subjects were invited to repeat a FPG test and 75-gram 2-hour oral glucose tolerance test (2h-OGTT) to determine the glycemic change within a period of 18 months. Normoglycaemia was defined as FPG<5.6 mmol/L and 2h-OGTT<7.8 mmol/L. Stepwise logistic regression model was developed to predict the regression-to-normoglycaemia with non-invasive variables, using a randomly selected training dataset (810 subjects). The model was validated on the remaining testing dataset (387 subjects). Area under the receiver-operating-characteristic-curve (AUC) and Hosmer-Lemeshow test were used to evaluate discrimination and calibration of the model. A nomogram was constructed based on the model. Results: 180 subjects (15.0%) had normoglycaemia based on the repeated FPG and 2h-OGTT results at follow-up. Subjects without central obesity or hypertension, with moderate-to-high level physical activity and a lower baseline FPG level were more likely to regress to normoglycaemia. The prediction model, including central obesity in combination with physical activity, base FPG level, and hypertension, had acceptable discrimination (AUC=0.705) and calibration (p=0.840). Conclusion: Central obesity is one of the key determinants of regression-to-normoglycaemia among IFG patients. The simple-to-use nomogram could facilitate identification of subjects with low-risk of progression to DM, thus aid in clinical decision-making and resource prioritization in the primary care setting.