Combining Fasting Plasma Glucose with Gamma-glutamyl Transferase Improves the Sensitivity to Predict Incident Diabetes in Asian Indian Men with Impaired Glucose Tolerance.
OBJECTIVE
To study the associations of baseline gamma-glutamyltransferase (GGT) and alanine transaminase (ALT) with incident diabetes among Asian Indian men with impaired glucose tolerance (IGT).


METHODS
In a 2 year prospective, randomised, controlled primary prevention study of diabetes, among 537 IGT men aged 35-55 years, 123 incident diabetes (DM) cases occurred. Anthropometric {body mass index (BMI), waist circumference (WC)}, and laboratory measurements (fasting, 30 min and 2 hr plasma glucose (2 hr PG), HbA1c and plasma insulin, lipid profile, ALT, GGT) were estimated at baseline (Clinical Trial Identification No: NCT00819455). Predictive associations of baseline GGT and ALT values during the study were assessed using appropriate statistical methods.


RESULTS
Baseline GGT but not ALT was significantly higher in incident diabetes cases. Mean (95% CI) GGT decreased in subjects who reverted to normal glucose tolerance (NGT), whereas it increased in subjects who deteriorated to diabetes (NGT:-3.5 (-6.4 to -0.6); IGT:0.3 (-3.0 to 2.4); DM:8.3 (3.6 to 13.0) UL(-1); P < 0.0001). The risk of DM significantly increased with increasing baseline GGT after adjusting for confounders such as BMI, alcohol drinking, 2 hr PG and insulin resistance (2.02[1.35-3.02]; P = 0.001). Receiver operating characteristic curve showed that the model comprising of baseline fasting plasma glucose (FPG) and GGT (area-under-curve(AUC)[95% CI]: 0.668 [0.613-0.722]; P < 0.0001) was equally sensitive in identifying subjects with risk of diabetes as compared to 2 hr PG (AUC [95% CI]: 0.670 [0.614-0.725]; P < 0.0001) and HbA1c (AUC [95% CI]: 0.677 [0.619-0.734]; P < 0.0001) alone.


CONCLUSIONS
GGT was an independent predictor of incident diabetes. Combination of GGT and FPG offers a simple and sensitive tool to identify subjects at high risk of developing diabetes.