Comparison of serum fructosamine and blood glucose concentrations as indices of glycaemic control in non-insulin dependent diabetic out-patients

The usefulness and validity of blood glucose measurement as an index of diabetic control were assessed with reference to serum fructosamine. Two hundred and twenty-eight non-insulin dependent diabetic out-patients were studied in the usual clinical setting. Fasting blood glucose (FBG) concentration was positively correlated with serum fructosamine (r = 0.42, t = 6.78 p less than 0.01). On the basis of their serum fructosamine concentrations, patients were divided into 3 groups. They were good control (fructosamine less than or equal to 288 umol/l), acceptable control (fructosamine less than or equal to 320 umol/l) and poor control groups (fructosamine greater than 320 umol/l). The mean fasting blood glucose concentration was significantly higher in the latter than the former 2 groups. However, at each level of control, there was a wide range of FBG concentrations. Thus, the value of FBG in predicting glycaemic control is limited. Its positive predictive value was only 32%, and its overall accuracy as an index of diabetic control was only 58% though its negative predictive value was high (93%). In 162 patients with poor diabetic control as indicated by their serum fructosamine concentrations, 81 (50%) of them had FBG less than 10 mmol/l on their clinic visit day. Fasting blood glucose is therefore not a reliable measure of good diabetic control, though it is useful in predicting poor control. FBG is simple to measure, cheap and rapidly available on clinic day, thus ensuring its continuing use. Doctors should be aware of its limitations and should not rely solely on FBG to assess diabetic control.
Study site: Diabetic clinic, Hospital Mentakab, Pahang, Malaysia