AUTOANTIBODIES TO GLUTAMIC-ACID DECARBOXYLASE AND PHENOTYPIC FEATURESASSOCIATED WITH EARLY INSULIN-TREATMENT IN INDIVIDUALS WITH ADULT-ONSET DIABETES-MELLITUS

We investigated the association of serum antibodies to glutamic acid d ecarboxylase (GADab) with early start of insulin treatment (less than or equal to 1 year from diagnosis, or less than or equal to 2 years fr om diagnosis) using data from a representative sample of 374 adult-ons et insulin-treated individuals from the Tasmanian Diabetes Register. F urthermore, we examined whether this association was stronger than the phenotypic characteristics (age at diagnosis, sex, family history of diabetes, level of obesity, duration of diabetes) often used for diabe tes classification. In this cohort, 35.9 % of males and 38.5 % of fema les were GADab positive. Within the first year from diagnosis, 78.4 % of GADab positive people compared to 44.0 % of GADab negative people ( p < 0.001) had started insulin treatment. Univariate associations with insulin treatment less than or equal to 1 year from diagnosis include d GADab positivity, no family history of diabetes, lower BMI for men, and GADab positivity and lower BMI for women. In multivariate models, significant associations with insulin treatment less than or equal to 1 year from diagnosis included a family history of diabetes (OR = 0.47 , 95 % CI = 0.23-0.95) and GADab positivity (OR = 2.19, 95 % CI = 1.01 -4.73) for men, but only GADab positivity (OR = 7.53, 95 % CI = 3.09-1 8.30) for women. Age at diagnosis was not associated with insulin trea tment less than or equal to 1 year or less than or equal to 2 years fr om diagnosis for either sex. These findings indicate that a positive G ADab test result is strongly associated with start of insulin treatmen t within 1 or 2 years from diagnosis, more so than characteristics suc h as level of obesity and age at diagnosis. (C) 1998 John Wiley & Sons , Ltd.