Diagnostic value of fasting capillary glucose, fructosamine and glycosylated haemoglobin in detecting diabetes and other glucose tolerance abnormalities compared to oral glucose tolerance test

New diagnostic criteria for diabetes mellitus recommend lowering of the fasting plasma glucose to 7.0 mmol/l. In contrast to recommendations of the American Diabetes Association (ADA), WHO recommends using the oral glucose tolerance test (OGTT) in clinical practice. In this study, based on OGTT results and WHO 1998 criteria, we determined if measuring fasting capillary glycaemia (FCG) along with fructosamine and/or glycosylated haemoglobin allows the detection of glucose tolerance abnormalities better than FCG alone. OGTT was performed in 538 patients. Serum fructosamine was determined in 480 of the patients, and glycosylated haemoglobin in 234 of the patients. According to WHO 1998 criteria, the patients were divided into groups due to glucose tolerance abnormalities. Fructosamine correlated stronger with 2-h post-load glucose concentrations than with FCG. HbA1c correlated stronger with FCG than with 2-h post-load glucose. Combined use of fructosamine and FCG predicted 2-h post-load glucose better than combined use of FCG and HbA1c. Receiver operating characteristic curve analyses showed that FCG was the best criterion in discriminating diabetes. Combined use of FCG and fructosamine slightly improved the ability to discriminate glucose tolerance abnormalities from normal glucose tolerance. FCG is the most effective predictor of 2-h post-load glucose and the best criterion for discriminating diabetes and other glucose tolerance abnormalities from normal glucose tolerance. Fructosamine is a potentially useful post-load glycaemia index. OGTT is irreplaceable in identification of patients with high post-load glycaemia.