Fasting plasma glucose and glycated haemoglobin in the screening of diabetes and impaired glucose tolerance

The use of fasting plasma glucose (FPG) only has been proposed for the screening and diagnosis of diabetes, but its sensitivity has been reported to be unsatisfactory. The use of HbA(1C), alone or combined with FPG, has been suggested for the screening of diabetes and impaired glucose tolerance (IGT). In a sample of 1215 adult subjects without previously known diabetes, we assessed the sensitivity and specificity of FPG and HbA(1C) in diagnosing diabetes and IGT, determined by oral glucose tolerance test (OGTT). All lean diabetic patients, and 85% of overweight and obese diabetic individuals. had FPGgreater than or equal to7 mmol/l. FPG>6.1 mmol/l had a sensitivity of 98.8% and a specificity of 32.9%; HbA(1C) had a lower specificity and sensitivity for the screening of diabetes. A screening strategy for diabetes based on FPG, with OGTT in all overweight subjects with FPG>6.1 mmol/l, is suggested. Neither FPG nor HbA(1C) is effective in the screening of IGT; although combined FPG and HbA(1C) could be useful for case finding, screening for IGT with OGTT is advisable in all subjects at high risk.