A special acknowledgment to the TEDDY families for their continued participation in this wonderful study. Funding. was impartial of GADA versus IAA as a first-appearing autoantibody (adjusted hazard ratio [HR] 1.12; 95% CI 0.88C1.42; = 0.36). Second-appearing GADA, IAA, IA-2A, or ZnT8A conferred an increased risk of T1D compared with children who remained positive for a single autoantibody, e.g., IAA or GADA second (adjusted HR 6.44; 95% CI 3.78C10.98), IA-2A second (adjusted HR 16.33; 95% CI 9.10C29.29; 0.0001), or ZnT8A second (adjusted HR 5.35; 95% CI 2.61C10.95; 0.0001). In children who developed a distinct second autoantibody, IA-2A (adjusted HR 3.08; 95% CI 2.04C4.65; 0.0001) conferred a greater risk of progression to T1D as compared with GADA or IAA. Additionally, both a younger initial age at seroconversion and shorter time to the development of the second-appearing autoantibody increased the risk for T1D. CONCLUSIONS The hierarchical order of distinct autoantibody spreading was independent of the first-appearing autoantibody type and was age-dependent and augmented the risk of progression to T1D. Introduction -cell autoantibodies are predictors of type 1 diabetes (T1D) (1,2) and are currently the most reliable indicator of preclinical disease. The presence of two or more autoantibodies against the four major autoantigens (insulin, GAD, insulinoma antigen-2 [IA-2], and zinc transporter 8 [ZnT8]) have been shown to confer the highest risk of T1D and was recently defined as stage 1 T1D (3). -cell autoantibodies develop prior to and usually persist over time in the progression to clinical onset of T1D (stage 3). The age at appearance of specific -cell autoantibodies varies (4C6). GAD antibody (GADA) or insulin autoantibody (IAA) predominate as first-appearing autoantibodies (7,8). SAR7334 IAA appearance peaks within the first 2 years of life. In contrast, GADA appears between ages 3 and 5 years in children with either increased genetic risk or family history of T1D (7C9). IA-2 autoantibody (IA-2A) and Rabbit Polyclonal to RPAB1 ZnT8 autoantibody (ZnT8A) generally appear after the initial islet autoantibody seroconversion (6,8,10,11) in more advanced stages of the disease process (3,12C14). Recent studies have focused on the appearance of the first-appearing autoantibody (7,8) with limited discussion of the specific second-appearing autoantibody (8). The Finnish T1D Prediction and Prevention (DIPP) study (8) reported that IAA as a second-appearing SAR7334 autoantibody peaked in the first 5 years of life and followed a similar pattern to the first-appearing GADA, whereas GADA peaked within the first 2 years of life and mostly occurred after IAA. More recently, the DIPP study reported that the initial age at seroconversion was only associated with IAA-initiated seroconversion and further progression to T1D (15). However, because of a varied autoantibody screening interval, further exploration after the first 2 years of life was limited. Other studies assessing the presence of autoimmunity and combinations of autoantibodies were carried out where the actual order of appearance could not be distinguished because of annual screening (16,17) or capture was at the time of or just prior to diagnosis (1,11,18C22). These previous studies assessing risk from single to multiple autoantibodies showed that increased risk was associated with a younger age, HLA-DR-DQ, and IAA as the first-appearing autoantibody (16,17). In addition to HLA class II risk, a recent study from the Belgian Diabetes Registry (23) reported that specific HLA class I alleles accelerated progression from multiple autoantibody positivity to T1D in those 40 years with a family history of T1D. Specifically, HLA-A*24 was associated with an accelerated progression in HLA-DQ8+ relatives who developed either IA-2A or ZnT8A, whereas HLA-B*18 was associated with accelerated progression in HLA-DQ2+ relatives who developed both IAA and GADA (23). Moreover, non-HLA single nucleotide polymorphisms SAR7334 (SNPs), such as those in the gene region (rs1004446) and protein tyrosine phosphatase nonreceptor type 22 (= 54) or were deemed HLA-DR-DQ ineligible based on study criteria (= 120) (Supplementary Fig. 1 and Supplementary Table 1). As the focus of this analysis was to examine autoantibody spreading, the analyses were restricted to the development of the first-appearing IAA single (=.