Now valid is fasting plasma glucose as a parameter of glycemic control in non-insulin-using patients with type 2 diabetes?

OBJECTIVE - To assess the value of fasting blood glucose as a parameter for glycemic control in type 2 diabetic patients not using insulin. RESEARCH DESIGN AND METHODS - In 1,020 type 2 diabetic patients treated wit h diet or oral hypoglycemic agents (OHAs), measurements of fasting plasma g lucose (FPG) and HbA(1c) were taken. In 617 patients, the measurement could be repeated after 3 months. Cross-sectional correlation coefficients were calculated for the association between HbA(1c) and FPG. Receiver-operating characteristic (ROC)-curve analyses were applied to examine the performance of FPG as a diagnostic test for Hba(1c). Longitudinally, the change in FPG was compared with the change in HbA(1c), with both correlation measures an d ROC curve analyses. RESULTS - Correlation coefficients between HbA(1c) and FPG and between FPG change and HbA(1c) change were 0.77 and 0.65, respectively. ROC curve analy sis showed that HbA(1c) is difficult to predict from FPG values: 66% of the patients with good HbA(1c) (<7.0%) were identified as such by FPG values < 7.8 mmol/l. As a test for HbA(1c) change, FPG change performed moderately: the highest combined values of sensitivity and specificity (87.7 and 57%, r espectively) were reached at a cutoff point of zero in the range of FPG cha nge values. CONCLUSIONS - FPG and HbA(1c) values that do not correspond are not rare in type 2 diabetic patients on diet or OHA. treatment. HbA(1c) is difficult t o predict from FPG values, and even more difficult is the prediction of HbA (1c) changes from FPG changes.