Evaluation of the new fasting plasma glucose cutpoint of 7.0 mmol/l in detection of diabetes mellitus in the Thai population.

To determine whether a fasting plasma glucose (FPG) cutpoint of 7.0 mmol/l can be appropriately used for detection of diabetes mellitus (DM) in the Thai population, different FPG cutpoints were evaluated for their efficacy in the diagnosis of DM. A plasma glucose level of > or = 11.1 mmol/l at 2 h after a 75-g oral glucose tolerance test (OGTT) was used as the gold standard criterion for diagnosis of DM. OGTT was performed in 496 subjects who were at risk of developing diabetes. They were 120 males and 376 females, 14-76 years old (mean +/- S.D. = 45.0 +/- 12.2 years). Plasma glucose level was determined in NaF preserved plasma using the glucose oxidase method. Diagnosis of DM was made in 22.8% of cases by the gold standard criterion as compared to 4.2% by using FPG values of > or = 7.8 mmol/l. The sensitivity of the FPG cutpoint of 7.8 mmol/l was 18.6%. Diagnosis of DM using FPG > or = 7.0 mmol/l improved the sensitivity to 33.6% with a positive predictive value of 100% and highest Youden's index of 0.836. The receiver operating characteristic curve of FPG revealed the best cutpoint to lie between 5.6-6.0 mmol/l. A FPG cutpoint of < 6.0 mmol/l over-estimated the prevalence of diabetes. DM and impaired glucose tolerance were noted in 65.6 and 29.5% of the subjects who had FPG values between 6.0 and 6.9 mmol/l, respectively. We conclude that FPG cutpoint of 7.0 mmol/l is applicable to a high risk Thai population for detection of DM. OGTT is recommended for definitive determination of glucose tolerance status in those individuals with FPG values between 6.0 and 6.9 mmol/l.