Here we investigated the prevalence rates and titration of BP-IgG autoantibodies using three different ELISA systems—BP180 NC16A ELISA, full-length BP180 ELISA (BP180-FL ELISA), and BP230 ELISA—for diagnosing BP in 275 cases of T2DM treated with or without DPP-4i. This evidence concerns the gene COL17A1 and type 2 diabetes mellitus.