INS and diabetes mellitus: According to our previously mentioned criteria, the best cut-off point of non-stimulated C-peptide was 0.95 ng/mL, while the predictive indices for insulin use were 0.8 for sensitivity and 0.92 for specificity at DM diagnosis, 0.83 for sensitivity and 0.92 for specificity at one year after DM diagnosis, and 0.84 for sensitivity and 0.94 for specificity at two years after DM diagnosis (Table 2).