Latent autoimmune diabetes in adults in a population-based cohort of Polish patients with newly diagnosed diabetes mellitus a value higher than 1 U/ml according to recom- mendations for the kit. Binding percentage of 125I- insulin higher than mean value ±3 SD was consid- ered positive for IAA. Available RIA commercial kits were used for GADA and IAA measurements. Beta cell function and insulin sensitivity were estimat- ed by homeostatic model assessment (HOMA2). Terms and classifications Patients were classified as having type 1 diabetes if insulin treatment was started within 6 months of diagnosis. Diagnosis of LADA was made accord- ing to the criteria proposed by the Immunology Dia- betes Society and Action LADA [1]. Those who were aged ≥ 30 years at diagnosis, autoantibody posi- tive, and insulin independent during the first 6 months after diagnosis were considered to have LADA. Participants who were GADA or IAA negative and insulin independent for 6 months or more after diagnosis were considered to have type 2 diabetes. Statistical analysis The incidence was calculated as the number of new cases of disease in a defined group of people over a specific time. Data are shown as mean ± SD. The Mann-Whitney U test and Spearman correla- tion test were applied. A p value of < 0.05 was con- sidered statistically significant. Results Incidence rate of diabetes in Bialystok population In 2003, 231 cases of newly diagnosed diabetes in a population of 188 738 inhabitants in the 20 to 65 years age range were found. The incidence of known diabetes in this population was therefore 1.22 per 1000 per year (95% confidence interval (CI) 1.07-1.39 per 1000 per year). Characteristics of the study participants Two hundred and twelve patients (212) partici- pated in the study. This represents 91% of the sam- ple collection. Among 212 participants, 54.2% were males. The mean HbA1c was 7.2 ±1.9%. The mean body mass index (BMI) in the whole diabetic pop- ulation was 29.2 ±5.4%. Percentage of GADA/IAA autoantibody positivity The percentage of GADA/IAA-positive patients in this cohort was 10.3% (n = 22; 95% CI 0.66-1.54). Anti-glutamic acid decarboxylase antibody was present in 7.0% (n = 15; 95% CI 4.11-11.4), and IAA in 4.5% (n = 9; 95% CI 2.07-7.79) of people with newly diagnosed diabetes. Clinical features associated with GADA/IAA autoantibody positivity In all groups, the presence of autoantibody was correlated with the age at diagnosis (r = –0.187, p < 0.05), body mass index (BMI) (r = –0.182, p < 0.05), waist (r = 0.214, p < 0.05), fasting C peptide (r = –0.300, p < 0.0001), fasting insulin (r = –0.213, p < 0.0001), HOMA 2% B (r = –0.219, p < 0.01), HOMA2-IR (r = 0.303, p < 0.001). Subtypes of diabetes In our cohort, 87.7% (n = 186; 95% CI 7.57-10.1) were diagnosed with type 2 diabetes. Latent autoimmune diabetes in adults was diagnosed in 8.9% (n = 19; 95% CI 5.55-13.74). Subtype of dia- betes in relation to auto-antibodies: the majority (63%) of patients with LADA had anti-GAD anti- bodies (n = 12); IAA were present in eight patients with LADA. One patient had both antibodies GADA and IAA. Up to 36% of patients diagnosed with LADA had IAA present. The diagnosis of type 1 diabetes was made in 3.3% of individuals (n = 7; 95% CI 1.44-6.54). Among them, three subjects were positive for autoimmune antibody (n = 2 GADA, n = 1 both GADA and IAA) and four negative. Characteristics of LADA and type 2 diabetes Patients with LADA were compared to those with type 2 diabetes and were found to be younger at the time of diagnosis, had lower BMI, waist cir- cumstance, fasting C peptide level and insulin, low- er beta cell function (HOMA 2%B) and at the same time were less insulin resistance than patients with type 2 diabetes (HOMA2-IR). Characteristics of LADA and type 2 diabetes are depicted in Table I. Discussion This is the first study to examine the epidemiol- ogy of LADA in the Polish population. We identified and tested more than 90% of newly diagnosed cas- es of diabetes during 1 year in the Bialystok area. The incidence of LADA was 10 per 100 000 per year and was similar to that described for the population living in South Wales (9 per 100 000 per year) [5]. The proportion of LADA among newly diagnosed patients with diabetes was 8.9%. Taking into account that in this study the majority of patients were diagnosed with type 2 diabetes, the observed proportion is similar to that found in the UKPDS, Finish and Swedish studies [2-4], and higher than detected in the Horn study, mainly due to the dif- ferent age of the population tested [15]. Compared to patients with type 2 diabetes, patients with LADA were younger at the time of diagnosis, had lower BMI, waist circumstance, Arch Med Sci 3, June / 2012 493