Screening for diabetes mellitus - a two-step approach in individuals with impaired fasting glucose improves detection of those at risk of complications

Aims To compare the new American Diabetes Association (ADA) fasting plasma glucose (FPG) criteria to the 1985 World Health Organization (WHO) 2-h post glucose (2hPG) criteria when used for screening of those with no prior his tory of diabetes mellitus. Methods The study included 3407 subjects without a history of diabetes in w hom both FPG and 2hPG were available from the 1992 Singapore National Healt h Survey. The agreement (kappa) between FPG and 2hPG for the diagnosis of D M was assessed. The optimal cut-off of FPG for the detection of individuals with 2hPG greater than or equal to 11.1 mmol/l was determined by receiver- operating characteristics analysis. Results The prevalence of diabetes diagnosed by FPG alone was 7.3% compared to 8.4% diagnosed by 2hPG. The prevalence of impaired fasting glucose was 8.0%. FPG and 2hPG showed moderate agreement(kappa = 0.646, 95% confidence interval 0.584-0.708). Age, ethnic group and obesity did not affect the deg ree of agreement. Of those with 2hPG greater than or equal to 11.1 mmol/l, 40.8% had FPG in the non-diabetic range while 24.8% of those with FG greate r than or equal to 7.0 mmol/l had 2hPG in the non-diabetic range. The optim al FPG for the detection of 2hPG greater than or equal to 11.1 mmol/l was 6 .1 mmol/l. Oral glucose tolerance tests (OGTT) in those with 6.0 mmol/ < FP G < 7.0 mmol/l resulted in the diagnosis of diabetes in 90.7% of individual s at risk of microvascular complications. Conclusions FPG provides a simple screening test for diabetes, which shows moderate agreement with the 2hPG. A two-step strategy of OGTT in those with impaired fasting glucose improves the detection of at-risk individuals. Ho wever, diabetes should not be diagnosed on a single test. The test should b e repeated on another day if an individual tests positive for diabetes.