1301-P: Glucagon Stimulation Test—Is It Time for an Easy Interpretation Proposal?

Background and Aims. Guidelines suggest the use of c-peptide in case of ambiguous diabetes. Glucagon stimulation test (GST), with the intravenous administration of glucagon 1 mg, is a 10-minutes test and it is suitable in clinical practice. It can describe residual beta-cell function although an easy way to identify from this test the type of diabetes or need for insulin in the short term is not available. The aims of this pilot study were to describe c-peptide response during GST and to identify classes of subjects corresponding to different types of diabetes or need of insulin.

Methods: We retrospectively recorded c-peptide levels of adults with ambiguous diabetes who underwent to GST. We divided subjects in 4 classes according to basal c-peptide (BCP) and to mean stimulated c-peptide increase (SCPi): class 1 (BCP <0.5 and SCPi <0.7 mmol/L from basal levels); class 2 (BCP <0.5 mmol/L and SCPi ≥0.7 mmol/L), class 3 (BCP ≥0.5 mmol/L and SCPi <0.7 mmol/L); class 4 (BCP ≥0.5 mmol/L and SCPi ≥0.7 mmol/L). Data about antibody positivity for anti-GAD and I.C.A. (Ab+) and need for insulin within two months were recorded.

Results: We enrolled 61 subjects, age 48.4 (14.6) years [mean (standard deviation)]. 7 subjects (11%) were included in class 1. Mean basal c-peptide was 0.3 mmol/L. 5 subjects (71%) were Ab+ and all required insulin. None of the participants were included in class 2. 18 subjects (29.5%) were included in class 3. Mean basal c-peptide was 1.0 mmo/L. 11 (61%) of class 3 subjects were Ab+ and required insulin within 2 months. 36 subjects (59.5%) were included in class 4. Mean basal c-peptide was 1.8 mmol/L. 5 (13%) of them required insulin therapy within 2 months and 4 (11%) were Ab+. Class 1 and 3 presented with lower BMI than class 4 (p<0.001).

Conclusions: In those preliminary data subjects in class 1 are more likely type 1 diabetes, while subjects in class 3 are more likely T1DM or LADA requiring insulin in the short term. Those preliminary data suggest an easy interpretation for GST to include it more frequently in clinical practice.