Aim of study: to assess the prevalence of markers of autoimmune destruction of pancreatic b-cells (AIDb) in patients classified initially as Type-2 diabetes mellitus (Type-2 DM). Subjects: 250 pati- ents subdivided according to the: 1. BMI and C-peptide, 2. type of treatment. Measured parame- ters: age, BMI, C-peptide, autoantibodies directed against: glutamic acid decarboxylase (GADA), islet cells (ICA), thyrosinphosphatase (IA-2) and insulin (IA-A). Results: GADA (and other AIDb markers) positivity varied from < 5% in patients with overweight /obesity (> 27 kg.m -2 ) and nor- mal/ increased C-peptide (> 0.32 nmol/l) to > 30% in non-obese patients with low C-peptide. Conclu- sion: Proportion of diabetics classified initially as having Type-2DM have had in fact slowly evolving autoimmune (Type-1) diabetes mellitus (LADA). In some patients both AID and insulin resistance may coexist in parallel. Pitfalls in interpretation of results of GADA, such as border positivity and similar, are discussed.

        Key words: NIDDM - Latent autoimmune - Diabetes mellitus - LADA - GADA - ICA - IA-A - C-peptid - Classification.