The prevalence of diabetes and thyroid related autoantibodies in Sri Lankan children with type 1 diabetes and their unaffected siblings - The utility of a new screening assay

BACKGROUND

There is limited information about diabetes and thyroid related autoantibodies in children with type 1 diabetes (T1D) or their siblings in Sri Lanka.

OBJECTIVES

To assess in T1D children and their unaffected siblings the prevalence of autoantibodies to (1) glutamic acid decarboxylase (GADA), insulinoma associated antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A) using 3 Screen ICA™ (3-Screen) and individual ELISA assays; (2) insulin (IAA); and (3) thyroid peroxidase (TPOA), thyroglobulin (TgA) and the TSH receptor (TSHRA).

METHODS

We selected - (a) consecutive T1D children, and (b) their unaffected siblings of both sexes, from the T1D Registry at Lady Ridgeway Hospital, Colombo.

RESULTS

The median age (IQR) of 235 T1D children and 252 unaffected siblings was 11 (8.4, 13.2) and 9 (5.4, 14.9) years respectively, and the duration of T1D was 23 (7, 54) months. (1) T1D children (a) 79.1% were 3-Screen positive; (b) all 3-Screen positives were individual antibody positive (GADA in 74%; IA-2A 31.1%; ZnT8A 38.7%); (c) and were younger (p=0.01 vs 3-Screen negatives); (d) multiple autoantibodies were present in 45.1%; (e) IA-2A (p=0.002) and ZnT8A (p=0.006) prevalence decreased with T1D duration. (f) TPOA and TgA prevalence was higher in T1D children compared to unaffected siblings (28%, p=0.001 and 31%, p=0.004, respectively). (2) Unaffected siblings (a) 6.3% were 3-Screen positive (p=0.001 vs T1D), and 2.4% were positive for IAA; (b) four subjects had two diabetes related autoantibodies, one of whom developed dysglycaemia during follow-up.

CONCLUSIONS

The 3-Screen assay, used for the first time in Sri Lankan T1D children and their siblings as a screening tool, shows a high prevalence of T1D related Abs with a high correlation with individual assays, and is also a helpful tool in screening unaffected siblings for future T1D risk. The higher prevalence of thyroid autoantibodies in T1D children is consistent with polyglandular autoimmunity.

HbA1c as a time predictive biomarker for an additional islet autoantibody and type 1 diabetes in seroconverted TEDDY children

OBJECTIVE

Increased level of glycated hemoglobin (HbA1c) is associated with type 1 diabetes onset that in turn is preceded by one to several autoantibodies against the pancreatic islet beta cell autoantigens; insulin (IA), glutamic acid decarboxylase (GAD), islet antigen-2 (IA-2) and zinc transporter 8 (ZnT8). The risk for type 1 diabetes diagnosis increases by autoantibody number. Biomarkers predicting the development of a second or a subsequent autoantibody and type 1 diabetes are needed to predict disease stages and improve secondary prevention trials. This study aimed to investigate whether HbA1c possibly predicts the progression from first to a subsequent autoantibody or type 1 diabetes in healthy children participating in the Environmental Determinants of Diabetes in the Young (TEDDY) study.

RESEARCH DESIGN AND METHODS

A joint model was designed to assess the association of longitudinal HbA1c levels with the development of first (insulin or GAD autoantibodies) to a second, second to third, third to fourth autoantibody or type 1 diabetes in healthy children prospectively followed from birth until 15 years of age.

RESULTS

It was found that increased levels of HbA1c were associated with a higher risk of type 1 diabetes (HR 1.82, 95% CI [1.57-2.10], p < 0.001) regardless of first appearing autoantibody, autoantibody number or type. A decrease in HbA1c levels was associated with the development of IA-2A as a second autoantibody following GADA (HR 0.85, 95% CI [0.75, 0.97], p = 0.017) and a fourth autoantibody following GADA, IAA and ZnT8A (HR 0.90, 95% CI [0.82, 0.99], p = 0.036). HbA1c trajectory analyses showed a significant increase of HbA1c over time (p < 0.001) and that the increase is more rapid as the number of autoantibodies increased from one to three (p < 0.001).

CONCLUSION

In conclusion, increased HbA1c is a reliable time predictive marker for type 1 diabetes onset. The increased rate of increase of HbA1c from first to third autoantibody and the decrease in HbA1c predicting the development of IA-2A are novel findings proving the link between HbA1c and the appearance of autoantibodies.

Evaluation of the RSR 3 screen ICA™ and 2 screen ICA™ as screening assays for type 1 diabetes in Sweden

AIM

The study aim was to evaluate the RSR 3 Screen ICA™ and 2 Screen ICA™ for detection of islet cell autoimmunity in healthy Swedish subjects and patients with newly diagnosed type 1 diabetes (T1D).

METHODS

3 Screen is designed for combined detection of autoantibodies to glutamic acid decarboxylase (GADA), to the islet antigen IA-2 (IA-2A) and to zinc transporter 8 (ZnT8A), while 2 Screen detects GADA and IA-2A. Serum samples from 100 T1D patients at onset and 200 healthy controls were studied.

RESULTS

3 Screen achieved 93% assay sensitivity and 97.5% specificity, while 2 Screen achieved 91% assay sensitivity and 98.5% specificity. Samples were also tested in assays for individual autoantibodies. There was only one 3 Screen positive healthy control sample (0.5%) that was positive for multiple autoantibodies (IA-2A and ZnT8A). In contrast, most of the 93 3 Screen positive patients were positive for multiple autoantibodies with 72% (67/93) positive for both GADA and IA-2A and 57% (53/93) positive for three autoantibodies (GADA, IA-2A and ZnT8A). Insulin autoantibodies (IAA, measured by radioimmunoassay) were positive in 13 patients and two healthy controls.

CONCLUSION

3 Screen achieved high sensitivity and specificity, suitable for islet cell autoimmunity screening in a healthy population. In the case of 3 Screen positivity, further assays for GADA, IA-2A and ZnT8A are required to check for multiple autoantibody positivity, a hallmark for progression to T1D. In addition, testing for IAA in children below two years of age is warranted.

Ten years follow up of first degree relatives of type 1 diabetes patients: presence of autoimmune biomarkers and the progression to diabetes in a retrospective cohort

OBJECTIVE

The aim of the study was to assess the autoimmunity in first degrees relatives (FDR) of patients with type 1 diabetes (T1DM) and the progression to T1DM after 10 years of follow up in the Brazilian population.

METHODS

Non-diabetic FDR of T1DM patients were interviewed and blood was drawn for autoantibodies measurement (GADA, IA-2A, IAA, ZnT8A). Serum samples were analyzed by standard radioligand binding assays performed at the Federal University of Rio de Janeiro (GADA, IAA and IA2A), and at the Skäne University Hospital, Sweden (ZnT8A). The FDR were interviewed by phone after 10 years to determine if they had developed T1DM. Descriptive statistical analysis was performed and results were described as means and standard deviation (SD).

RESULTS

81 individuals were analyzed. Thirteen subjects had positive autoantibodies associated with T1DM.10 were positive for 1 autoantibody and 3 subjects were positive for multiple autoantibodies (1 of them showed positivity for 2 autoantibodies - GADA, ZnT8A - and the other two were positive for 3 autoantibodies - GADA, IA2A, ZnT8A). The 3 subjects with multiple positive autoantibodies developed T1DM within 10 years.

CONCLUSION

In Brazilian FDR of T1DM patients, the positivity for multiple autoantibodies indicate a greater chance of progression to T1DM, similar to observed in Caucasians. ZnT8A was helpful in the risk assessment for T1DM development.

Association between islet autoantibodies and the prevalence of autoimmune uveitis

AIM

To evaluate the predictive value of islet autoantibodies for the diagnosis of autoimmune uveitis (AU), as well as to characterize the association bet ween islet autoantibodies and AU.

METHODS

Totally 97 patients with AU and 100 healthy persons without any autoimmune diseases as the control group were recruited. Multiple serum islet autoantibodies were measured using commercial enzyme-linked immunosorbent assay kits (ELISA). A supplementary questionnaire was used to complement the subject's demographics and clinical features. The level of glucose concentrations and white blood cells were measured. Conditional logistic regression was performed to estimate odds ratios (ORs), and 95% confidence intervals (CIs) of AU according to islet autoantibodies and to evaluate the predictive value of islet autoantibodies for AU diagnosis. Autoantibodies subgroups and other variables were included into analysis.

RESULTS

In AU patients, the prevalence of detecting at least one of the autoantibodies was 31.9% (31/97). The most frequent autoantibody was ZnT8A (30.9%), followed by GADA (11.3%), IA-2A (4.1%), ICA (2.1%) and IAA (2.1%). Islet autoantibodies were found to be correlated positively with AU diagnosis [OR (95%CI): 13.86 (3.28, 58.50), P<0.001]. Moreover, Zn-T8A was remarkably correlated with AU diagnosis [OR (95%CI): 6.13 (1.96, 19.17), P<0.001], In contrast, neither GADA nor other islet antibodies (IA-2A, ICA and IAA) showed any association with AU risk under an additive model.

CONCLUSION

The prevalence of islet antibodies, especially ZnT8A, in patients with AU is higher. Islet antibodies as well as novel biomarkers should be included in routine evaluation at AU and is a valuable biological marker to classify newly-diagnosed uveitis.

Islet Autoantibody Analysis: Radioimmunoassays

Type 1 diabetes (T1D) is a chronic inflammatory disease, caused by the immune mediated destruction of insulin-producing β-cells in the islets of the pancreas (Ziegler and Nepom, Immunity 32(4):468-478, 2010). Semiquantitative assays with high specificity and sensitivity for T1D are now available to detect antibodies to the four major islet autoantigens: glutamate decarboxylase (GADA) (Baekkeskov et al., Nature 347(6289):151-156, 1990), the protein tyrosine phosphatase-like proteins IA-2 (IA-2A) and IA-2β (Notkins et al., Diabetes Metab Rev 14(1):85-93, 1998), zinc transporter 8 (ZnT8A) (Wenzlau et al., Proc Natl Acad Sci U S A 104(43):17040-17045, 2007), and insulin (IAA) (Palmer, Diabetes Metab Rev 3(4):1005-1015, 1987). More than 85 % of cases of newly diagnosed or future T1D can be identified by testing for antibodies to GADA and/or IA-2A/IAA, with 98 % specificity (Bingley et al., Diabet Care 24(2):398, 2001). Overall, radioimmunoassay (RIA) is considered the de facto gold standard format for the measurement of T1D autoantibodies (Bottazzo et al., Lancet 2(7892):1279-1283, 1974; Schlosser et al., Diabetologia 53(12):2611-2620, 2010). Here we describe current methods for autoantibody measurement using RIA. These fluid phase assays use radiolabeled ligands and immunoprecipitation to quantify autoantibodies to GAD, IA-2, ZnT8, and insulin (Bonifacio et al., J Clin Endocrinol Metab 95(7):3360-3367, 2010; Long et al., Clin Endocrinol Metab 97(2):632-637, 2012; Williams et al., J Autoimmun 10(5):473-478, 1997).

Bridging-type enzyme-linked immunoassay for zinc transporter 8 autoantibody measurements in adult patients with diabetes mellitus

AIMS

A bridging-type ELISA for measuring autoantibodies to zinc transporter 8 (ZnT8A) was assessed using samples from different forms of diabetes mellitus.

METHODS

ZnT8A were measured using an ELISA in patients with type 1 diabetes mellitus (T1DM; n=94), latent autoimmune diabetes of adulthood (LADA; n=51), type 2 diabetes mellitus (T2DM; n=59) and healthy blood donors (HBD; n=200). ZnT8A in ELISA and immunoprecipitation assays (IPA) using ZnT8 dimer (W325/R325) and monomers (W325, R325 and Q325) were compared.

RESULTS

Inter- and intra-assay coefficients of variation (CV) were 7.1% and 1.7%, respectively (medium ZnT8A) and 8.5% and 2.7%, respectively (high ZnT8A). In the ELISA 51/94 (54.3%) T1DM, 16/51 (31.4%) LADA and 1/59 (1.7%) T2DM sera were ZnT8A positive. ROC analysis of T1DM and HBD for the ELISA showed 54% sensitivity and 99% specificity (cutoff 15u/mL) and AUC 0.80 (95% CI, 0.74-0.86). ELISA and IPA measurements were in very good agreement (r=0.856, k=0.889, n=204). Measurement of ZnT8A in addition to autoantibodies for GAD, IA-2 and insulin increased antibody positivity in T1DM by 4.3%, from 80.9% to 85.1%.

CONCLUSIONS

The bridging-type ELISA is a convenient and reproducible method for determination of ZnT8A in serum. Measurement of ZnT8A increased autoantibody positivity in adult T1DM.