Poster Presentation The 13th International Congress of the Immunology of Diabetes Society 2013

Late detection of latent autoimmune diabetes in adults associated with lower GAD antibody concentration (#78)

Spiros Fourlanos 1 , Leonard C Harrison 2 , Peter G Colman 1
  1. Royal Melbourne Hospital, Parkville, Victoria, Australia
  2. Walter & Eliza Hall Institute, Melbourne, Victoria, Australia

Background and Aim: 
Latent autoimmune diabetes in adults (LADA) is a slowly progressive form of adult-onset type 1 diabetes characterized by the presence of circulating islet autoantibodies, classically glutamic acid decarboxylase antibody positivity (GADA). Even though in newly detected autoimmune diabetes, GADA concentration is reported to inversely correlate with beta-cell function, in classical type 1 diabetes, the islet autoantibody concentration is recognized to decrease over time due to loss of beta cell mass and associated antigenic drive. Over time in patients with LADA, we hypothesize the GADA concentrations may decrease due to declining beta-cell mass. We therefore aimed to compare GADA concentration in LADA diagnosed early versus late. Methods: One hundred patients with LADA diagnosed at the Royal Melbourne Hospital were analysed for GADA concentration and the timing of detecting islet autoimmunity. GADA concentration was compared in LADA detected ‘Early’ (within 10 years of diabetes diagnosis) compared to ‘Late’ (after 10 years of diabetes diagnosis). Results: The median age of the entire cohort of LADA was 47.5 years (n=100, M=54, F=46).  In the ‘Early’ detection group (n=51) the median time to detection of islet autoimmunity 0.7 years) whilst in the ‘Late’ group (n=49) the median time to detection of islet autoimmunity 12.9 years.  There was no difference in the median age at diagnosis of diabetes in the ‘Early’ group (median age 47.5 years) versus the ‘Late’ group (median age 47.6years). (GADA concentration was significantly lower in the ‘Late’ group compared to the ‘Early’ group (median IQR 61 [42-89] vs. 38 [12-78], P=0.033). There was no significant difference in IA2 Ab positivity or concentration between the two groups. Conclusion: Immunity to GAD may lessen with longer duration LADA. In long standing diabetes in adulthood lack of islet autoantibody positivity may not preclude the possibility of autoimmune diabetes.