COL17A1 and diabetes mellitus: BP180 NC16A ELISA, BP230 ELISA, and full-length BP180 ELISA detected BP autoantibodies in 1.8%, 2.2%, and 10.9% of 221 DM patients with DPP4i treatment, respectively, whereas these assays detected BP autoantibodies in 0%, 7.4%, and 5.6% of 54 DM patients without DPP4i treatment, respectively.