Combination Use Of HbA_1c And Plasma Glucose Improves The Efficiency Of HbA_1c In Diagnosing Diabetes In Chinese With Increased Risk For Diabetes

Objective: To evaluate whether combination of fasting plasma glucose (FPG) or 2h plasma glucose (2h-PG) after 75-g glucose load with HbA1c are effective in diagnosing diabetes in Chinese subjects with increased risk for diabetes.Research design and methods: A total of 1151 Chinese people with increased risk for diabetes were randomly included. All subjects had an OGTT test and HbA1c measurement. Receiver operating characteristic (ROC) curve analysis was performed to determine the sensitivity and specificity of either plasma glucose or HbA1c in diagnosing diabetes. Kappa (?) statistic was calculated as a measure of agreement between different diagnostic methods .Results: When OGTT was used as the reference test (i.e., FPG≥7.0 mmol/l and/or 2h-PG≥11.1 mmol/l) for diabetes diagnosis, the optimal values of HbA1c, FPG and 2h-PG in diagnosing diabetes are 6.1%, 6.9 mmol/l and 11.1 mmol/l, respectively. Applying the dual optimal cutpoint of FPG≥6.9 mmol/l and HbA1c≥6.1% or the dual optimal cutpoint of 2h-PG≥11.1 mmol/l and HbA1c≥6.1% for diabetes diagnosis, the specificity approached 99.6% and 100%, respectively. Which were much higher than that for HbA1c alone(89.1%). Patients diagnosed by the method of combination of FPG≥6.9 mmol/l and HbA1c≥6.1% or the method of combination of 2h-PG≥11.1 mmol/l and HbA1c≥6.1% had significantly higher FPG, 2h-PG, HbA1c and HOMA-IR (P<0.0001) than those of patients diagnosed by the other four diagnostic methods (FPG≥6.9 mmol/l alone, 2h-PG≥11.1 mmol/l alone, HbA1c≥6.1% alone and OGTT). While there were no significant differences in FPG, 2h-PG, HbA1c and HOMA-IR in patients diagnosed with diabetes by the method of combination of FPG≥6.9 mmol/l and HbA1c≥6.1% and the method of combination of 2h-PG≥11.1 mmol/l and HbA1c≥6.1% . There is high agreement for diabetes diagnosis between combination of FPG≥6.9 mmol/l or of 2h-PG≥11.1 mmol/l with HbA1c≥6.1% and OGTT (?=0.69, 95% CI 0.65-0.73 or ?=0.80, 95% CI 0.76-0.83, respectively ).Conclusions: Combination use of FPG or 2h-PG with HbA1c improves the specificity of HbA1c alone in diabetes diagnosis in Chinese high risk subjects, which results reduced false posotives. Both the method of FPG≥6.9 mmol/l+ HbA1c≥6.1% and the method of 2h-PG≥11.1 mmol/l+ HbA1c≥6.1% are effective methods for diabetes diagnosis.