Background: The glycemic thresholds for diabetes diagnosis have long been at the forefront of discussion. However, no information about glycemic cutoff points has been made available for the Chinese population. The aim of the present study was to examine the association of fasting plasma glucose (FPG), 2-h plasma glucose (2-h PG) and HbA(1)c levels with diabetic retinopathy (DR) and determine the associated cutoff levels in a Chinese population.
Methodology and principal findings: In a cross-sectional population-based sample of 2551 Chinese (representing a population of 1,660,500 in a Beijing district) between 18-79 years of age, the three glycemic measures were measured in a 75 g oral glucose tolerance test, and DR was assessed by two 45° color digital retinal images. The prevalence of DR increased in the ninth decile of each variable, corresponding to an FPG of ≥ 7.2 mmol/l, a 2-h PG of ≥ 10.7 mmol/l, and HbA(1)c of ≥ 6.4%, according to the Joinpoint regression method. After excluding individuals receiving antihyperglycemic medication, the prevalence significantly increased at an FPG of ≥ 6.8 mmol/l, a 2-h PG of ≥ 12.0 mmol/l, and HbA(1)c of ≥ 6.7%. The area under the ROC curve for all three measures showed no significant differences for detecting DR. After excluding individuals receiving antihyperglycemic medication, the three measures also showed no significant differences.
Conclusions and significance: A significant increase in retinopathy prevalence occurs among individuals with FPG ≥ 7.2 mmol/l, 2-h PG ≥ 10.5 mmol/and HbA(1)c ≥ 6.4%; and measuring FPG or HbA(1)c are equally reliable methods as measuring 2-h PG for the diagnosis of diabetes in the Chinese population.