Padoa, Carolyn J.Rheeder, PaulPirie, Fraser J.Motala, Ayesha A.Van Dyk, Jacobus C.Crowther, Nigel J.2020-03-312020-12Padoa, C.J., Rheeder, P., Pirie, F.J. et al. 2020, 'Identification of a subgroup of black South Africans with type 1 diabetes who are older at diagnosis but have lower levels of glutamic acid decarboxylase and islet antigen 2 autoantibodies', Diabetic Medicine, vol. 37, no. 12, pp. 2067-2074.0742-3071 (print)1464-5491 (online)10.1111/dme.14204http://hdl.handle.net/2263/73886AIMS : To compare the age at diagnosis and prevalence of islet autoantibody [glutamic acid decarboxylase (65 kDa) 65 and islet antigen 2] positivity in black and white participants with type 1 diabetes in South Africa, and to analyse the relationship between age at diagnosis and the presence of autoantibodies. METHODS : Participants were recruited from diabetes outpatient departments and autoantibodies to glutamic acid decarboxylase (65 kDa) and islet antigen 2 were measured by enzyme‐linked immunosorbent assay. RESULTS : We recruited 472 (353 black and 119 white) participants with type 1 diabetes. Age at diagnosis of diabetes was later in black (19.7 ± 10.5) than in white participants (12.7 ± 10.8 years; P < 0.001) with a median (interquartile range) disease duration of 5.0 (2.0–10.0) and 8.5 (4.0–20.0) years (P < 0.001), respectively. An older age at diagnosis (≥ 21 years) was more frequent in black (152 of 340, 45%) than in white participants (24 of 116, 21%; P < 0.001). The prevalence of islet antigen 2 autoantibodies was 19% (66/352) in black and 41% in white participants (48/118; P < 0.001). There was no significant difference in glutamic acid decarboxylase (65 kDa) autoantibody positivity between black (212/353, 60%) and white participants (77/117, 66%; P = 0.269). In black, but not white, participants the prevalence of both glutamic acid decarboxylase (65 kDa) and islet antigen 2 autoantibody positivity was significantly lower in participants diagnosed at age ≥ 21 years (P < 0.001 for both comparisons). CONCLUSIONS : The older age at diagnosis, lower prevalence of islet antigen 2 autoantibodies and a distinct subgroup of participants with type 1 diabetes with age at diagnosis of > 20 years in the black compared to white population suggest a difference in the immunological aetiology of type 1 diabetes in these two population groups.en© 2019 Diabetes UK. This is the pre-peer reviewed version of the following article : 'Identification of a subgroup of black South Africans with type 1 diabetes who are older at diagnosis but have lower levels of glutamic acid decarboxylase and islet antigen 2 autoantibodies', Diabetic Medicine, vol. 37, no. 12, pp. 2067-2074, 2020, doi : 10.1111/dme.14204. The definite version is available at : https://onlinelibrary.wiley.com/journal/14645491.AutoantibodiesBlack populationGAD65IA-2Older age at diagnosisSouth Africa (SA)Type 1 diabetesPostprint Article