Frequency of islet cell autoantibodies (IA-2 and GAD) in young Brazilian type 1 diabetes patients

Abstract

Type 1 diabetes, as an autoimmune disease, presents several islet cellspecific autoantibodies such as islet cell antibody (ICA), anti-insulin, anti-glutamic acid decarboxylase (GAD) and the antibody (Ab) against tyrosine phosphatase (PTP)-like protein known as ICA-512 (IA-2). In order to determine the frequency of the anti-GAD and anti-IA-2 autoantibodies in Brazilian type 1 diabetes patients we studied 35 diabetes mellitus (DM) type 1 patients with recent-onset disease (£12 months) and 37 type 1 diabetes patients with long-duration diabetes (>12 months) who were compared to 12 children with normal fasting glucose. Anti-GAD 65 and anti-IA-2 autoantibodies were detected with commercial immunoprecipitation assays. The frequency of positive results in recent-onset DM type 1 patients was 80.0% for GADAb, 62.9% for IA-2Ab and 82.9% for GADAb and/or IA-2Ab. The longduration type 1 diabetes subjects presented frequencies of 54.1% for GADAb and IA-2Ab, and 67.5% for GAD and/or IA-2 antibodies. The control group showed no positive cases. Anti-GAD and IA-2 assays showed a high frequency of positivity in these Brazilian type 1 diabetes patients, who presented the same prevalence as a Caucasian population.

Relationship between the prevalence of anti-glutamic acid decarboxylase autoantibodies and duration of type 1 diabetes mellitus in Brazilian patients

“…It is known that GADA tend to be less frequent in Black African patients with T1D (23). On the other hand, previous Brazilian studies have found a similar prevalence of GADA positivity in Brazilian and Caucasian European T1D (5,24). Finally, we believe that the lack of patients with a very recent diagnosis (<12 months) could be a major factor explaining the low prevalence of GADA in our study population, especially in the group with a shorter duration of the disease.…”

“…Even though the drop of prevalence in the first year of the disease is a possible explanation, most previous studies have reported a higher frequency of GADA in patients with T1D with a shorter duration of the disease regardless of whether this category comprised only individuals diagnosed for less than 1 year (5,12) or included patients with the duration of disease up to five years (25,26). Interestingly, studies that consider <2 or <5 years of disease in the recent diagnosis category have demonstrated a relatively lower prevalence of the antibody in these groups (54.9-56%), closer to our results (25,26).…”

“…Antibodies against GAD are detected in 50-85% of T1D patients with a recent diagnosis (3). Although some investigators have shown a higher prevalence of GADA in newly diagnosed patients than in individuals with a longer duration of diabetes, persistent positive results are found in many cases (3)(4)(5)(6)(7). As a matter of fact, GADA appears to be the ideal immune marker in patients already treated with insulin and with long-standing disease.…”

Latent autoimmune diabetes in adults (LADA): usefulness of anti-GAD antibody titers and benefit of early insulinization

“…This assay was previously evaluated by the laboratory, and the intra-assay and interassay coefficients of variation were 3.1 and 3.5%, respectively, for normal reference values. Sensitivity was 80% for type 1 diabetic patients with a recent diagnosis (15). The assay kits achieved good discrimination between cases and controls with an area under the curve and 90% adjusted sensitivity above the 75 th percentile for both, as recommended for a good quality assay (16).…”

Diabetes autoimune em adultos: características clínicas e autoanticorpos

“…Existem poucas referências considerando estes aspectos e a prevalência de anticorpos em diabéticos no nosso meio (21)(22)(23)(24)(25)(26)(27). Nós testamos autoanticorpos anti-GAD, anti-insulina e anti-ilhotas pancreáticas em pacientes com DM de início na idade adulta, com características clínicas iniciais de DM2, pertencentes a população com origem racial mista, composta de brancos (caucasianos), índios e negros com os seguintes objetivos: estabelecer a prevalência de LADA numa população de DM2 e caracterizar o fenótipo desse grupo.…”