Prevalência dos marcadores imunológicos Anti-GAD e Anti-IA2 em parentes de primeiro grau de diabéticos do tipo 1 em amostra da população da Grande São Paulo

BACKGROUND: Increasingly accurate prediction of Type1 Diabetes Mellitus (DM1), based on analysis of autoantibody markers, has become possible in first-degree relatives of patients with diabetes (PDM1). These markers indicate autoimmune process against pancreatic islet beta-cells. Anti-GAD and anti-IA2 are considered predictive of DM1, 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 DM1 patients first-degree relatives (PDM1) in a sample of the Brazilian population of Great Sao Paulo City. METHODS: Forty-eight children and adolescents PDM1 with median of age of 14.5 years (range 6.7 to 17.9 years). Anti-GAD and anti-IA2 was mesured 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 PDM1(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 PDM1 and controls. CONCLUSION: The prevalence of anti-GAD has been more prevalent among the PDM1. No differences were observed between prevalences for anti-IA2 showed by PDM1 and controls.