ABSTRACT
In order to analyze the different parameters used in the interpretation of C-peptide response in a functional test, we compared a group of 26 type 1 diabetics aged 21.1 + 8.2 years, with a diabetes duration of 7.9 + 6.7 months, with a group of 24 non-diabetic subjects aged 25.0 + 4.4 years. A standard mixed meal of 317 kcal was used as a stimulus. Blood sampling for C-peptide determinations was performed at regular intervals. Although all the studied C-peptide variables were significantly lower in the diabetic group (P<0.0001), some overlapping of parameters was observed between the two groups. The highest degree of overlapping was found for basal value (BV) (30.8 percent) and percent increase (42.31 percent), and the lowest for incremental area, absolute increase, peak value (PV) (3.8 percent), and total area (7.7 percent) (X2 = 31.6, P<0.0001). We did not observe a definite pattern in the time of maximum response among the 21 diabetics who showed an increase in C-peptide levels after the stimulus. In this group, however, there was a highly significant number of late responses (120 min) (X2 = 5.7, P<0.002). Although BV showed a significant correlation with PV (rs = 0.95, P<0.0001), the basal levels of C-peptide did not differentiate the groups with and without response to the stimulus. We conclude that the diabetic group studied showed delayed and reduced C-peptide responses, and that the functional test can be an important tool for the evaluation of residual beta cell function.