Glycated serum proteins and glucose tolerance.

Glycated serum proteins (GSP), stable glycated hemoglobin (HbA1c) together with some metabolic parameters were evaluated in 120 subjects, 30 with normal glucose tolerance (NGT), 30 with impaired glucose tolerance (IGT), 30 with non-insulin-dependent diabetes mellitus (NIDD), and 30 with insulin-dependent diabetes mellitus (IDD). GSP levels were significantly higher in IGT, NIDD and IDD than in NGT. HbA1c levels were not significantly higher in IGT in comparison with NGT, but were significantly higher in NIDD and in IDD than in NGT and IGT. GSP correlated better than HbA1c with all metabolic parameters considered. Taking into account the distribution of the values, GSP showed a smaller overlap than HbA1c in all four groups studied. Moreover, only 9 subjects (30%) with IGT showed GSP levels above the normal range. Therefore, GSP assay is able to distinguish between normal and diabetic subjects but is unable by itself to discriminate subjects with normal from those with reduced glucose tolerance.