Autoantibodies to Glutamic Acid Decarboxylase and Insulin in Islet Cell Antibody Positive Presymptomatic Type 1 Diabetes Mellitus: Frequency and Segregation by Age and Gender

The frequency of antibodies to glutamic acid decarboxylase (GAD) and insulin (IAA) in presymptomatic Type 1 diabetes mellitus with a positive test for antibodies to islet cell antigen (ICA) was examined. Thirty‐two persons positive for ICA (> 10 JDF units) were tested 2 to 48 months before their ascertained onset of Type 1 diabetes. ICA was quantitated by immunofluorescence as JDF units, anti‐GAD by radioimmunoprecipitation and anti‐insulin by radioimmunoassay. There was a positive test for anti‐GAD in 25 (78%), and for IAA in 23 (72%), of the 32 prediabetic ICA‐positive subjects. Stratification according to age at the onset of diabetes showed differing frequencies of anti‐GAD and IAA in the prediabetic stage. Thus the positivity rate for anti‐GAD for 18 subjects older than 10 years at onset of diabetes was 83%, and for 14 aged 10 or younger at onset was 71%; conversely, the rate for IAA for 18 subjects older than 10 at onset was 56% and for 14 aged 10 or less at time of onset was 93% (p = 0.01). The frequency of anti‐GAD was higher in females (88%) than males (71%) whereas the frequency of IAA was higher in males (82%) than in females (60%). Since autoantibodies to GAD and insulin occur in presymptomatic Type 1 diabetes with differences in frequencies by age and gender, the stimuli to autoimmunity may operate differently at different ages, and may also be gender‐related. 1994 Diabetes UK