Clinical Investigation Of Idiopathic Type 1 Diabetes

Part I Diagnosis and Clinical Characteristics of Idiopathic Type 1 DiabetesObjective: To establish a diagnostic procedure for idiopathic type 1 diabetes, and to disclose the clinical characteristics of idiopathic type 1 diabetes in the present study population.Design: Cross-sectional study and hospital-based case-control studyParticipants and methods: Sixty-eight patients with unprovoked ketosis or ketoacidosis at presentation participated in our study. Step 1, they were tested for GAD-Ab^ IA-2Ab and IAA with radioligand assay. Step 2, those who were negative for the presence of these 3 antibodies were tested for TGA and TPO antibodies with RIA. Step 3, those who were negative for all detected antibodies were genotyped in term of HLA-DQA1 and DQB1 with sequence-based genotyping (SET) method. Autoantibody-negative patients were subdivided into group A (with HLA-DQ risk alleles) and group B (without type 1 diabetes susceptible alleles) .Clinical characteristics, including age, sex, mode of presentation, BMK islet beta-cell function and current treatment were compared between autoantibody-positive and -negative patients and between group A and B.Results: The 50%(34/68) patients were found to be positive for 1 or more islet autoantibodies. From patients who were negative for islet autoantibodies, one was found to be positive for TPO-Ab. That was, Among the 68 cases, 51.5% (35/68) were positive for autoantibodies, while 48.5% (33/68)were negative for all the antibodies tested. As for genetic analysis, 20 of the 33 seronegative patients carried 1-4 HLA-DQ risk alleles, while the other 13 did not carry any type 1 diabetes susceptible alleles tested. Compared with autoantibody-nagative patients, younger age of onset , less obesity , more severe DKA and lower C peptide were found in autoantibody-positive patients . Compared with group B, less BMI, more severe DKA, lower C peptide were observed in group A. Duringfollow-up, 69.2%(9/13) patients in group B ceased insulin therapy and maintain acceptable glycemic control by either diet or oral hypoglycemic agents (OHA), while only 35% (7/20) patients in group A ceased insulin therapy and treated with OHA. Among those who keeped on using insulin, the patients in group A needed higher dose than that in group B.Conclusion: l)Autoantibody-negative diabetic patients displayed more type lA-like features if carrying susceptible HLA-DQ genotypes. Only those who were autoantibody negative and did not carry susceptible HLA-DQ genotypes can be diagnosed as type IB diabetes. 2)Idopathic type 1 diabetes does existed in Chinese. And atypical diabetes mellitus (ADM) was the most common phenotype of idiopatic type 1 diabetes in our study population.