Islet autoantibodies in Latvian subjects with non-insulin-dependent diabetes mellitus: slow-onset type 1 diabetes or polyendocrine autoimmunity?

In Latvia diabetes mellitus is diagnosed using the WHO's clinical criteria; assays for the detection of autoantibodies are not available, and hence slowly progressive autoimmune diabetes is likely to be missed. Autoantibodies against glutamic acid decarboxylase (GAD65) and protein tyrosine phosphatase (IA-2) among patients with clinically diagnosed NIDDM identify group of patients with slow-onset type 1 diabetes or LADA. The aim of this study was to estimate the risk of polyendocrine autoimmunity among clinically diagnosed NIDDM patients from Latvia. One hundred NIDDM patients and 100 healthy controls were tested for GAD65 and IA-2 autoantibodies as well as 21-hydroxylase (21-OH) and tissue transglutaminase (TTG) antibodies by RIA assay. Age at onset was greater than or equal to 30 years, and duration of disease less than 5 years. Of 100 patients, 85 were on oral hypoglycemic agents and 15 were on insulin. Body mass index (BMI) under 19 was recorded in 1% (1 of 100 cases), while overweight (BMI > 25.5 in females and 27 in males) was documented in 45% (45 of 100 cases). GAD65 antibodies were found in 30 of 100 (30%) and IA-2 antibodies in 40 of 100 (40%) patients. Either GAD65 or IA-2 antibodies were found in 55 of 100 (55%). None of the patients carried antibodies against 21-OH and only 1 of 100 (1%) carried antibodies against TTG. From the results obtained in our study we conclude that in Latvian adult NIDDM subjects, islet autoantibodies identify groups of slow-onset type 1 diabetes but not polyendocrine antoimmunity.