Background: Increasingly accurate prediction of Type I Diabetes Mellitus (DMI), based on analysis of autoantibody markers, has become possible in first-degree relatives of patients with diabetes (PDMI). These markers indicate autoimmune process against pancreatic islet beta-cells. Anti-GAD and anti-IA2 are considered predictive of DMI, whose prevalences are considerably variable in different populations studied. There are few data about the frequency of these markers on the Brazilian population. The aim of this study is determine the prevalence of positivity for anti-GAD and for anti-IA2 among DMI patients first-degree relatives (PDMI) in a sample of the Brazilian population of Great São Paulo City.
Methods: Forty-eight children and adolescents PDMI with median of age of 14.5 years (range 6.7 to 17.9 years). Anti-GAD and anti-IA2 was measured by radioassay (Kronus , USA). The cut-off limit for both antibodies was set at the 99th percentile from normal subjects serum samples (anti-GAD: n=194; Median of age=13.4 yrs; range 9.7 to 64 yrs; anti-IA2: n=71; Median of age=12.6; range 11.1-15.2 yrs). A subject was considered to be positive for anti-IA2 if specific binding exceeded the 99th among the analysis of 71 subjects. The limit to positivity was 1.72 U/ml to anti-GAD and 0.97 U/ml to anti-IA2.
Results: Five PDMI (10.4%) have showed positivity to anti-GAD, with significantly higher prevalence than controls (P<0.01). The anti-IA2 prevalence rate seems to be equivalent between PDMI and controls.
Conclusion: The prevalence of anti-GAD has been more prevalent among the PDMI. No differences were observed between prevalences for anti-IA2 showed by PDMI and controls.