Investigations: autoAtbs (anti-islet cell, anti-GAD [specific but not sensitive]; also: anti-insulin, anti-Tyr phosphatases, anti-IA-2, anti- IA-2 beta, anti-ZnT8), specific HLA polymorphisms (DR3 DQ2 [~90% of T1DM cases], DR4-DQ8), other genetic polymorphisms (preproinsulin. PTPN22 gene, CTLA-4), viral serology (viral-specific Atbs)