Islet antibodies and remaining beta-cell function 8 years after diagnosis of diabetes in young adults: a prospective follow-up of the nationwide Diabetes Incidence Study in Sweden.

OBJECTIVES: To establish the prevalence of remaining beta-cell function 8 years after diagnosis of diabetes in young adults and relate the findings to islet antibodies at diagnosis and 8 years later.
DESIGN: Population-based cohort study.
SETTING: Nationwide from all Departments of Medicine and Endocrinology in Sweden.
SUBJECTS: A total of 312 young (15-34 years old) adults diagnosed with diabetes during 1987-88. MAIN OUTCOME MEASURE: Plasma connecting peptide (C-peptide) 8 years after diagnosis. Preserved beta-cell function was defined as measurable C-peptide levels. Three islet antibodies - cytoplasmic islet cell antibodies (ICA), glutamic acid decarboxylase antibodies and tyrosine phosphatase antibodies - were measured.
RESULTS: Amongst 269 islet antibody positives (ab+) at diagnosis, preserved beta-cell function was found in 16% (42/269) 8 years later and these patients had a higher body mass index (median 22.7 and 20.5 kg m-2, respectively; P = 0.0003), an increased frequency of one islet antibody (50 and 24%, respectively; P = 0.001), and a lower prevalence of ICA (55 and 6%, respectively; P = 0.007) at diagnosis compared with ab+ without remaining beta-cell function. Amongst the 241 patients without detectable beta-cell function at follow-up, 14 lacked islet antibodies, both at diagnosis and at follow-up.
CONCLUSIONS: Sixteen per cent of patients with autoimmune type 1 diabetes had remaining beta-cell function 8 years after diagnosis whereas 5.8% with beta-cell failure lacked islet autoimmunity, both at diagnosis and at follow-up.