Glutamic acid decarboxylase and islet antigen 2 antibody profiles in people with adult‐onset diabetes mellitus: a comparison between mixed ethnic populations in Singapore and Germany

AIM: To gain insight into the presence of islet cell autoimmunity in an ethnic Asian compared with a white European population. METHODS: For this cross‐sectional study we recruited people with adult‐onset diabetes (age of diagnosis 20–60 years), at tertiary referral centres in Germany (n=1020) and Singapore (n=1088). Glutamic acid decarboxylase and islet antigen 2 antibodies were measured according to Islet Autoantibody Standardization Program protocols. RESULTS: The prevalence of glutamic acid decarboxylase antibody positivity was 13.9% (95% CI 12.1–16.0; P<0.001) in the white European cohort compared with 6.8% (95% CI 5.5–8.4; P<0.001) in the Asian cohort. Glutamic acid decarboxylase antibody positivity was 11.4% (95% CI 7.7–16.6) in Indian, 6.0% (95% CI 3.6–9.9) in Malay and 5.8% (95% CI 4.3–7.7; P<0.001) in Chinese participants. In the white European participants, the prevalence of islet antigen 2 antibody positivity was 7.8% (95% CI 6.4–9.4) compared with 14.8% (95% CI 12.8–17.0; P<0.001) in the Asian cohort as a whole, and among the three ethnicities in the Asian cohort it was 12.4% (95% CI 8.6–17.7) in Indian, 16.8% (95% CI 12.6–22.2) in Malay and 15.7% (95% CI 13.2–18.6) in Chinese participants. Double antibody positivity was seen in 5.7% (95% CI 4.5–7.1) of white European participants compared with 1.6% (95% CI 1.0–2.5; P<0.01) of Asian participants. In the white European cohort, those who were glutamic acid decarboxylase autoantibody‐positive had a lower BMI than those who were autoantibody‐negative, but this trend was absent in the Asian cohort. CONCLUSIONS: A marked prevalence of islet cell autoimmunity was observed in people with adult‐onset diabetes. While glutamic acid decarboxylase antibodies were more frequent in the European cohort, islet antigen 2 antibody positivity was highest in the three ethnic groups in Singapore, suggesting ethnic‐specific differences in antibody profiles.