Results showed that 16% T1D, 93% T2D and 96% non-diabetic controls had C-peptide ≥0.2 nmol/l on the fasting sample. PGCP was measured in 22 T1D and 14% had PGCP levels ≥0.32 nmol/l showing some form of endogenous insulin secretion. ***The different diabetes study groups were based on WHO diabetes classification (1980s); therefore a higher chance of misclassification within the diabetes groups. Here, CPQ is linked to type 2 diabetes mellitus.