Fluctuations in GAD65 antibodies after clinical diagnosis of IDDM in young children

OBJECTIVE - To investigate whether the presence of GAD antibodies at onset of IDDM correlates to a more aggressive rate of β-cell destruction after clinical onset. RESEARCH DESIGN AND METHODS - We studied GAD antibodies at onset of disease, after 1 year, and after 6 years in 33 consecutively referred children (mean age 8.08, range 1.7-16.3). In a subset of 11 patients, GAD antibodies were studied very frequently. The correlation between GAD antibodies and clinical parameters, including glycosylated hemoglobin, residual insulin secretion, and insulin dosage, was evaluated. RESULTS - GAD antibody titers were highly variable. Four patients became GAD antibody positive weeks to years after clinical onset. Other patients switched between testing positive and negative for GAD antibodies shortly after clinical onset. No correlation was found between the presence of GAD antibodies and the rate of β-cell destruction, but patients with high GAD antibody indexes at onset had significantly higher glycosylated hemoglobin levels. CONCLUSIONS - GAD antibodies at clinical onset do not predict the rate of β-cell destruction in young children with newly diagnosed IDDM. The highly variable GAD antibody levels suggest variation of the autoimmune process.