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Aim: This study aimed to evaluate characteristics of autoimmunity in individuals who have a type 2 diagnosis and are relatives of children with type 1 diabetes. Methods: Pre‐diagnosis samples (median 17 months before onset) from relatives who were later diagnosed with type 2 diabetes were measured for autoantibodies to glutamate decarboxylase 65 (GADA), islet antigen‐2 (IA‐2A), zinc transporter 8 (ZnT8A) and insulin (IAA) as well as the type 1 diabetes genetic risk score (GRS2). Associations between islet autoantibodies, insulin treatment and GRS2 were analysed using Fisher's exact and t‐tests. Results: Among 226 relatives (64% men; mean age at sampling 41 years; mean age 54 years at diagnosis), 32 (14%) were islet autoantibody‐positive for at least one autoantibody more than a decade before diagnosis. Approximately half of these (n = 15) were treated with insulin. GADA‐positivity was higher in insulin‐treated relatives than in non‐insulin‐treated relatives (12/18 [67%] vs. 6/18 [33%], p < 0.001). IAA‐positivity was observed in 13/32 (41%) of relatives with autoantibodies. GRS2 scores were increased in autoantibody‐positive relatives (p = 0.032), but there was no clear evidence for a difference according to treatment (p = 0.072). Conclusion: This study highlights the importance of measuring islet autoantibodies, including IAA, in relatives of people with type 1 diabetes to avoid misdiagnosis. [ABSTRACT FROM AUTHOR]

Autoantibodies to glutamate decarboxylase (GADA) are widely used in the prediction and classification of type 1 diabetes. GADA radiobinding assays (RBAs) using N-terminally truncated antigens offer improved specificity, but radioisotopes limit the high-throughput potential for population screening. Luciferase-based immunoprecipitation system (LIPS) assays are sensitive and specific alternatives to RBAs with the potential to improve risk stratification. The performance of assays using the Nanoluc luciferase (Nluc)-conjugated GAD65 constructs, Nluc-GAD65(96-585) and full length Nluc-GAD65(1-585), were evaluated in 434 well-characterized serum samples from patients with recent-onset type 1 diabetes and first-degree relatives. Nonradioactive, high-throughput LIPS assays are quicker and require less serum than RBAs. Of 171 relatives previously tested single autoantibody positive for autoantibodies to full-length GAD65 by RBA but had not progressed to diabetes, fewer retested positive by LIPS using either truncated (n = 72) or full-length (n = 111) antigen. The Nluc-GAD65(96-585) truncation demonstrated the highest specificity in LIPS assays overall, but in contrast to RBA, N-terminus truncations did not result in a significant increase in disease-specificity compared with the full-length antigen. This suggests that binding of nonspecific antibodies is affected by the conformational changes resulting fromaddition of the Nluc antigen. Nluc-GAD65(96-585) LIPS assays offer low-blood-volume, high-specificity GADA tests for screening and diagnostics. [ABSTRACT FROM AUTHOR]

Background: Zinc transporter 8 autoantibodies (ZnT8A) are thought to appear close to type 1 diabetes (T1D) onset and can identify high-risk multiple (≥2) autoantibody positive individuals. Radiobinding assays (RBA) are widely used for ZnT8A measurement but have limited sustainability. We sought to develop a novel, high-performance, non-radioactive luciferase immunoprecipitation system (LIPS) assay to replace RBA. Methods: A custom dual C-terminal ZnT8 (aa268-369; R325/W325) heterodimeric antigen, tagged with a NanoluciferaseTM (Nluc-ZnT8) reporter, and LIPS assay was developed. Assay performance was evaluated by testing sera from new onset T1D (n = 573), healthy schoolchildren (n = 521), and selected first-degree relatives (FDRs) from the Bart's Oxford family study (n = 617; 164 progressed to diabetes). Results: In new-onset T1D, ZnT8A levels by LIPS strongly correlated with RBA (Spearman's r = 0.89; P < 0.0001), and positivity was highly concordant (94.3%). At a high specificity (95%), LIPS and RBA had comparable assay performance [LIPS pROC-AUC(95) 0.032 (95% CI: 0.029–0.036); RBA pROC-AUC(95) 0.031 (95% CI: 0.028–0.034); P = 0.376]. Overall, FDRs found positive by LIPS or RBA had a comparable 20-year diabetes risk (52.6% and 59.7%, respectively), but LIPS positivity further stratified T1D risk in FDRs positive for at least one other islet autoantibody detected by RBA (P = 0.0346). Conclusion: This novel, high-performance, cheaper, quicker, higher throughput, low blood volume Nluc-ZnT8 LIPS assay is a safe, non-radioactive alternative to RBA with enhanced sensitivity and ability to discriminate T1D progressors. This method offers an advanced approach to current strategies to screen the general population for T1D risk for immunotherapy trials and to reduce rates of diabetic ketoacidosis at diagnosis. The LIPS method for measurement of autoantibodies to zinc transporter 8 (ZnT8A) can replace the radiobinding assay. This method also offers an advanced approach to current strategies to screen the general population for type 1 diabetes risk for immunotherapy trials and to reduce rates of diabetic ketoacidosis at diagnosis. Graphical Abstract [ABSTRACT FROM AUTHOR]

Context: National databases can be used to investigate diabetes prevalence and health care use. Guideline-based care can reduce diabetes complications and morbidity. Yet little is known about the prevalence of diabetes and compliance with diabetes care guidelines among rural residents and whether different national databases provide similar results. Purpose: To examine rural-urban differences in the prevalence of diabetes and compliance with guidelines, and to compare the Behavioral Risk Factor Surveillance System (BRFSS) and the Medical Expenditures Panel Survey (MEPS). Methods: Data for 2001-2002 were analyzed and compared by rural-urban status. Prevalence was calculated as simple unadjusted, weighted unadjusted, and weighted adjusted using a multivariate approach. Results from the 2 databases were compared. Findings: A slightly higher prevalence of diabetes among rural residents, 7.9% versus 6.0% in MEPS and 7.6% versus 6.6% in BRFSS, was found and persisted after adjustment for age, BMI, insurance coverage, and other demographic characteristics (adjusted OR 1.16 [1.02-1.31] in MEPS; 1.19 [1.01-1.20] in BRFSS). Rural persons in MEPS were less likely to receive an annual eye examination (aOR = 0.85) and a feet check (aOR = 0.89). A significantly (P less than 0.05) smaller proportion of rural residents in BRFSS received an annual eye examination (aOR = 0.88), feet check (aOR = 0.85), or diabetes education (aOR = 0.83). Rural residents in both datasets were more likely to get a quarterly HbA1c test done. Conclusion: Rural residents in both datasets had higher prevalence of diabetes. Though not always statistically significant, the trend was to less guideline compliance in rural areas.

Aims: Some childhood type 1 diabetes cases are islet autoantibody negative at diagnosis. Potential explanations include misdiagnosis of genetic forms of diabetes or insufficient islet autoantibody testing. Many NHS laboratories offer combinations of three autoantibody markers. We sought to determine the benefit of testing for additional islet autoantibodies, including insulin (IAA) and tetraspanin 7 (TSPAN7A). Methods: Radiobinding assays (RBAs) were used to test for four islet autoantibodies in children with newly diagnosed type 1 diabetes (n = 486; 54.1% male; median age 10.4 years [range 0.7–18.0]; median duration 1 day [range −183 to 14]). Islet autoantibody negative children were tested for TSPAN7A using a luminescence‐based test. Where available, islet cell antibody (ICA) and human leucocyte antigen (HLA) data were considered. Results: Using three autoantibody markers, 21/486 (4.3%) children were autoantibody negative. Testing for IAA classified a further 9/21 (42.9%) children as autoantibody positive. Of the remaining 12 (2.5%) autoantibody negative children, all were TPAN7A negative, seven were ICA negative and one was positive for the protective variant DQB1*0602. One was subsequently diagnosed with Maturity Onset of Diabetes in the Young, but follow‐up was not available in all cases. Conclusions: Using highly sensitive assays, testing for three autoantibodies fails to detect islet autoimmunity in approximately 1/20 children diagnosed with type 1 diabetes. Testing for IAA in children <5 years and GADA in those >10 years was the most effective strategy for detecting islet autoimmunity. The ability to test for all islet autoantibodies should inform clinical decisions and make screening for monogenic diabetes more cost‐effective. [ABSTRACT FROM AUTHOR]