Measurement of GAD Antibody and HLA Antigens in Classification of Diabetes

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Since acute-onset insulin-dependent diabetes mellitus (IDDM) usually demonstrates a greater number of HLA antigens related to IDDM than slowly progressive IDDM (SPIDDM), the type of diabetes may be affected by a dosage effect of HLA antigens. The purpose of this study is to elucidate the dosage effect of HLA antigens in modifying the type of diabetes. We assayed antibodies to glutamic acid decarboxylase (GADab) in 253 non-insulin-dependent diabetes mellits (NIDDM) patients and 17 IDDM patients. We assayed HLA antigens (class I A, B, C antigens, class II DR, DQ antigens) in 7 of 8 GADab-positive NIDDM patients and 3 GADab-positive acute-onset IDDM patients, whose disease etiologies may be related to the background of autoimmunity. We tried to score the association of HLA antigens with IDDM as positive or negative in each patient. If the patients had one HLA antigen related to IDDM, they were given one point. If they had one HLA antigen showing a negative association with IDDM, one point was subtracted from the score. HLA scores of GADab-positive patients with NIDDM tended to have a lower score, but exceptionally there were a few higher HLA scores among NIDDM patients. Both GADab-positive and negative IDDM patients tended to have higher HLA scores.Our results suggest that measurement of HLA antigens as well as GADab can be of clinical value in predicting the type of diabetes. Moreover, it may be possible to detect patients who should receive insulin during the early stage of GADab-positive NIDDM.