gms | German Medical Science

Objective: The aim of this analysis is to compare screening strategies with haemoglobin A1c (A1C), fasting plasma glucose (FPG) or combined measures in the identification of individuals at high risk for diabetes.

Methods: Applying American Diabetes Association (ADA) thresholds for FPG and A1C screening, 6,803 subjects free of diabetes were classified as non-diabetic, pre-diabetic and possibly diabetic by FPG (<100, 100-125 and >125mg/dl) and A1C (<5.7, 5.7-6.4 and >6.4%) [1]. Hazard ratios, sensitivity and specificity were estimated for individuals with pre-diabetes with respect to incident diabetes in the following five years. Areas under the receiver operating characteristic curves (AUC) were estimated for levels of FPG≤125mg/dl and A1C≤6.4% in diabetes prediction.

Results: Although FPG and A1C screenings poorly agreed in classifying individuals as pre-diabetic, hazard ratios [95% confidence interval] for incident diabetes were similarly increased in univariate models in the two pre-diabetic groups: FPG 100-125mg/dl, 4.72 [3.69; 6.05]; A1C 5.7-6.4%, 3.97 [3.05; 5.23]. A1C and FPG had comparable AUCs (FPG, 0.732; A1C, 0.725) and consequently similar five-year sensitivities and specificities for their pre-diabetes definitions (when the lower cut-off for A1C-defined pre-diabetes was increased to a level between 5.8% and 5.9%). Combining A1C and FPG increased the AUC to 0.778, and a further increase to 0.817 was seen with additional inclusion of conventional risk factors.

Conclusions: FPG and A1C have comparable (yet insufficient) abilities in identifying individuals at high risk for diabetes. Effectiveness of a diabetes screening program could be improved by a risk score including FPG and A1C.