ANTI-CAD ANTIBODIES IN CHINESE PATIENTS WITH YOUTH AND ADULT-ONSET IDDM AND NIDDM

An autoimmune basis for the pathogenesis of insulin-dependent diabetes mellitus (IDDM) is supported by the frequent presence of autoantibodi es - islet cell antibodies (ICAs) and GAD antibodies (GADab). However, in Chinese patients with clinical IDDM, a low prevalence of ICAs was observed. In non-insulin-dependent diabetic (NIDDM) patients, it has b een suggested that the presence of GADab may identify a subset of late nt autoimmune diabetes in adults (LADA). We determined the frequency o f GADab in a large group of 134 IDDM and 168 NIDDM Chinese patients, a nd assessed the relation with ICAs status. Results showed that 39.6% I DDM and 16.1% NIDDM patients had GADab, and 20.1% and 4.8%, respective ly had detectable ICAs. Frequency of GADab positivity was not influenc ed by whether the patients had youth or adult-onset IDDM or NIDDM, or by duration of diabetes. NIDDM patients seropositive for GADab shared similar clinical characteristics and fasting C-peptide levels with tho se who were GADab negative. Presence of GADab therefore did not serve to identify a subgroup of patients with latent or slow-onset IDDM. Hal f (53%) of our IDDM patients had neither GADab nor ICAs. The reason fo r this observation is unclear. One theory is that other autoantigens y et to be identified may be contributory. Alternatively, in the Chinese , autoimmunity may not be the major factor in the pathogenesis of IDDM .