Latent autoimmune diabetes in adults (LADA) in South Wales: incidence and characterization

To define the incidence and characteristics of latent autoimmune diabetes in adults (LADA).

We estimated the incidence of LADA by examining the incidence of Type 2 diabetes and calculating the proportion that were antibody positive. The incidence of Type 2 diabetes was calculated by analysis of computer records of 35 out of 36 general practices in Swansea. In addition, thirty-two practices participated in recruiting people with Type 2 diabetes to have glutamic acid decarboxylase (GAD) antibody testing.

The crude proportion of Type 2 patients testing positive for GAD antibodies (GADA) was 4.0% (28/683). This figure did not change when we analysed only the practices that tested more than 60% of all eligible patients. In these practices, 79% (387/487) of all eligible patients were GADA tested and 14/387 [3.6% (95% confidence interval: 2.1-6.1%)] were classified as having LADA. This gives an incidence of LADA of 9 per 100,000 (95% confidence interval: 4.4-17.8 per 100,000) people per year registered with a general practitioner. Patients testing positive for GADA were more likely to have a lower body mass index, other antibodies, to present with acute symptoms and to have higher glycated haemoglobin.

This is the first study of the incidence of LADA in primary care. People with LADA make up a significant proportion of people with apparent Type 2 diabetes. Patients with LADA are likely to be symptomatic, have poorer glycaemic control and have other autoimmune antibodies.