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 β‐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 β‐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 β‐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 β‐cell function. Amongst the 241 patients without detectable β‐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 β‐cell function 8 years after diagnosis whereas 5.8% with β‐cell failure lacked islet autoimmunity, both at diagnosis and at follow‐up.