GAD65 antibody prevalence and association with c-peptide, HLA class II alleles in Beninese patients with type 1 diabetes

Background: Antibodies to glutamic acid decarboxylase and particularly their isoforms in 65 kDa are one of markers for the diagnosis of the type 1 diabetes (T1D). The aim of this study is to assess the prevalence of GAD65 antibodies (GAD65Ab) and investigate the association of GAD65Ab with C-peptide values, HLA Class II alleles genotyping. The diagnosis of T1D was set up according to American Diabetes Association criteria.Methods: Radioimmunoassay was used to determine the GAD65Ab and C-peptide values. Class II HLA genotyping was performed in 51 patients with T1D and 51 healthy unrelated as control by using the PCR-SSP method. The sensitivity and specificity of the tests were calculated by standard formula.Results: Result revealed that GAD65Ab were present in 74.5% (38/51) of the patients with T1D. There was no significant difference between the positivity or the negativity of GAD65Ab and gender, onset and duration of diabetes, frequencies of HLA-DR4, HLA-DR3-DR4, HLA-DQB1*0201. However, GAD65Ab values are linked to C-peptide concentration (χ2 =15.73, P=0.0001), the presence of HLA-DR3 (χ2 =9.75, P= 0.002), HLA-DQA1*0501 (χ2 =4.09, P= 0.043) alleles. The GAD65Ab test sensitivity and specificity were 74.5% and 94.1%, respectively. The C-peptide test showed a sensitivity around 82.4 % and 86.3 % for the specificity.Conclusions: GAD65Ab showed to be a valuable early predictive marker and is associated with the risk to develop of T1D