The diagnostic value of fasting plasma glucose, 2 h plasma glucose after glucose loading, and HbA1C to diabetes mellitus

A total of 6 656 residents aged above 35 years in Hengli, Dongguan, were included in this epidemiologic investigation. A questionnaire survey was performed. Body height, weight, waist circumference, hip circumference, and blood pressure were measured. The plasma lipid, fasting plasma glucose(FPG), HbA1C, and 2 h plasma glucose(2hPG)levels were detected. The test was repeated one week later if only one index was increased without any symptoms of diabetes mellitus. The diagnostic values of FPG, HbA1C, and 2hPG in diabetes mellitus were explored. The results showed that at the first week, 800 subjects were initially diagnosed as cases of diabetes mellitus by only one of the elevated FPG, HbA1Cor 2hPG values. The rates of single elevations of FPG, HbA1C, and 2hPG were 42.0%, 55.3%, and 67.1% respectively. The rates of elevation of FPG+ HbA1C, FPG+ 2h PG value, and HbA1C+ 2hPG value were 68.8%, 79.8%, and 91.0% respectively. Among 800 patients, who had only one elevation of those three indices without symptoms of diabetes mellitus, FPG, HbA1C, and 2hPG were repeated by the second week. The recurrence rate of elevation of FPG, HbA1C, and 2hPG was 27.6%, 74.3%, and 31.4% respectively. 503 individuals had got the final diagnosis of diabetes mellitus, among whom the rates of single elevation in FPG, HbA1C and 2hPG were 55.7%, 76.9%, and 69.8% respectively; and the rates of elevation of FPG+ HbA1C, FPG+ 2hPG, and HbA1C+ 2hPG were 87.3%, 78.7%, and 96.8% respectively. These results suggest that using one index of FPG, HbA1Cor 2hPG may lead to miss diagnosis of diabetes mellitus. The combination of those three indices may reduce miss diagnosis. HbA1C alone is better than the other two indices, and HbA1C+ 2hPG combination was better than the other combinations for diagnosing diabetes mellitus. (Chin J Endocrinol Metab, 2015, 31: 443-446) Key words: Diabetes mellitus; Fasting plasma glucose; 2 h plasma glucose after glucose loading; HbA1C; Diagnosis value