Ethnic variation in phenotype and autoantibody number in new-onset Type 1 diabetes (T1D) in a UK cohort: (ADDRESS-2)

Background: Type 1 diabetes (T1D) phenotype has been explored in predominantly white populations. People of non-white ethnicities diagnosed with T1D are reportedly less likely to be autoantibody positive. We studied differences in characteristics of people with T1D from 3 ethnicities: white European (WE), Asian (A) and black African or Caribbean (AC) with autoantibody number. 

Methods: People with clinically assigned T1D were recruited into ADDRESS-2 within 6 months of diagnosis. Islet autoantibodies (AAb) (GADA, IA2A and ZnT8A) were measured by radioimmunoassay in participants up to 1-year post diagnosis. AAb status was categorised as negative, 1 (positive to single AAb) and 2+ (positive to 2 or 3 AAbs). 

Results: 2,178 participants were studied: 15% were AAb negative, 25% had 1 AAb and 60% had 2+ AAbs, with significant ethnic differences according to AAb status (negative: 90.2% (WE), 5.4% (A), 4.4% (AC); 1 AAb: 94%, 3%, 3%; 2+ AAb: 97%, 2%, 1%; p<0.001).

In AAb negative individuals, differences included median age at diagnosis (years) (WE 31.4; A 28.8; AC 44.0; p<0.01); BMI (kg/m2) in adults (WE 26.7; A 26.5; AC 29.2; p=0.02) and BMI z-scores in children (WE 0.38; A -1.31; AC 2.04; p=0.01); and ketoacidosis at presentation (WE 37%; A 43%; AC 93%; p<0.001).

Individuals with 1 AAb differed between ethnic groups in median age at diagnosis (WE 26.1; A 12.7, AC 21.1; p=0.005); BMI in adults (WE 23.8; A 20.3; AC 24.4; p=0.05); and, in adults, median insulin dose (u/kg/day) (WE 0.36; A 0.55; AC 0.43; p=0.03).

In individuals with 2+ AAbs the only significant inter-ethnic difference was median insulin dose in children (WE 0.43; A 0.59; AC 0.52; p<0.001).

Conclusion: T1D phenotype differs across ethnic groups, according to autoantibody number, with the most marked differences seen for AAb negative individuals. Fewer differences were observed with increasing AAb number (negative, 1 AAb, 2+ AAbs), suggesting increasing inter-ethnic homogeneity in the diagnosis of T1D with increasing AAb numbers.