Use of self-collected capillary blood samples for islet autoantibody screening in relatives: a feasibility and acceptability study

AIMS

To evaluate the feasibility of using self-collected capillary blood samples for islet autoantibody testing to identify risk in relatives of people with Type 1 diabetes.

METHODS

Participants were recruited via the observational TrialNet Pathway to Prevention study, which screens and monitors relatives of people with Type 1 diabetes for islet autoantibodies. Relatives were sent kits for capillary blood collection, with written instructions, an online instructional video link and a questionnaire. Sera from capillary blood samples were tested for autoantibodies to glutamic acid decarboxylase, islet antigen-2, insulin and zinc transporter 8. 'Successful' sample collection was defined as obtaining sufficient volume and quality to provide definitive autoantibody results, including confirmation of positive results by repeat assay.

RESULTS

In 240 relatives who returned samples, the median (range) age was 15.5 (1-49) years and 51% were male. Of these samples, 98% were sufficient for glutamic acid decarboxylase, islet antigen-2 and zinc transporter 8 autoantibody testing and 84% for insulin autoantibody testing and complete autoantibody screen. The upper 90% confidence bound for unsuccessful collection was 4.4% for glutamic acid decarboxylase, islet antigen-2 and/or zinc transporter 8 autoantibody assays, and 19.3% for insulin autoantibodies. Despite 43% of 220 questionnaire respondents finding capillary blood collection uncomfortable or painful, 82% preferred home self-collection of capillary blood samples compared with outpatient venepuncture (90% of those aged <8 years, 83% of those aged 9-18 years and 73% of those aged >18 years). The perceived difficulty of collecting capillary blood samples did not affect success rate.

CONCLUSIONS

Self-collected capillary blood sampling offers a feasible alternative to venous sampling, with the potential to facilitate autoantibody screening for Type 1 diabetes risk.

β-cell specific T-lymphocyte response has a distinct inflammatory phenotype in children with Type 1 diabetes compared with adults

AIM

To examine the hypothesis that the quality, magnitude and breadth of helper T-lymphocyte responses to β cells differ in Type 1 diabetes according to diagnosis in childhood or adulthood.

METHODS

We studied helper T-lymphocyte reactivity against β-cell autoantigens by measuring production of the pro-inflammatory cytokine interferon-γ and the anti-inflammatory cytokine interleukin-10, using enzyme-linked immunospot assays in 61 people with Type 1 diabetes (within 3 months of diagnosis, positive for HLA DRB1*0301 and/or *0401), of whom 33 were children/adolescents, and a further 91 were unaffected siblings.

RESULTS

Interferon-γ responses were significantly more frequent in children with Type 1 diabetes compared with adults (85 vs 61%; P = 0.04). Insulin and proinsulin peptides were preferentially targeted in children (P = 0.0001 and P = 0.04, respectively) and the breadth of the interferon-γ response was also greater, with 70% of children having an interferon-γ response to three or more peptides compared with 14% of adults (P < 0.0001). Islet β-cell antigen-specific interleukin-10 responses were similar in children and adults in terms of frequency, breadth and magnitude, with the exception of responses to glutamic acid decarboxylase 65, which were significantly less frequent in adults.

CONCLUSIONS

At diagnosis of Type 1 diabetes, pro-inflammatory autoreactivity is significantly more prevalent, focuses on a wider range of targets, and is more focused on insulin/proinsulin in children than adults. We interpret this as indicating a more aggressive immunological response in the younger age group that is especially characterized by loss of tolerance to proinsulin. These findings highlight the existence of age-related heterogeneity in Type 1 diabetes pathogenesis that could have relevance to the development of immune-based therapies.

Seasonal variation in month of diagnosis in children with type 1 diabetes registered in 23 European centers during 1989-2008: little short-term influence of sunshine hours or average temperature

BACKGROUND

The month of diagnosis in childhood type 1 diabetes shows seasonal variation.

OBJECTIVE

We describe the pattern and investigate if year-to-year irregularities are associated with meteorological factors using data from 50 000 children diagnosed under the age of 15 yr in 23 population-based European registries during 1989-2008.

METHODS

Tests for seasonal variation in monthly counts aggregated over the 20 yr period were performed. Time series regression was used to investigate if sunshine hour and average temperature data were predictive of the 240 monthly diagnosis counts after taking account of seasonality and long term trends.

RESULTS

Significant sinusoidal pattern was evident in all but two small centers with peaks in November to February and relative amplitudes ranging from ± 11 to ± 38% (median ± 17%). However, most centers showed significant departures from a sinusoidal pattern. Pooling results over centers, there was significant seasonal variation in each age-group at diagnosis, with least seasonal variation in those under 5 yr. Boys showed greater seasonal variation than girls, particularly those aged 10-14 yr. There were no differences in seasonal pattern between four 5-yr sub-periods. Departures from the sinusoidal trend in monthly diagnoses in the period were significantly associated with deviations from the norm in average temperature (0.8% reduction in diagnoses per 1 °C excess) but not with sunshine hours.

CONCLUSIONS

Seasonality was consistently apparent throughout the period in all age-groups and both sexes, but girls and the under 5 s showed less marked variation. Neither sunshine hour nor average temperature data contributed in any substantial way to explaining departures from the sinusoidal pattern.

Trends in childhood type 1 diabetes incidence in Europe during 1989-2008: evidence of non-uniformity over time in rates of increase

AIMS/HYPOTHESIS

The aim of the study was to describe 20-year incidence trends for childhood type 1 diabetes in 23 EURODIAB centres and compare rates of increase in the first (1989-1998) and second (1999-2008) halves of the period.

METHODS

All registers operate in geographically defined regions and are based on a clinical diagnosis. Completeness of registration is assessed by capture-recapture methodology. Twenty-three centres in 19 countries registered 49,969 new cases of type 1 diabetes in individuals diagnosed before their 15th birthday during the period studied.

RESULTS

Ascertainment exceeded 90% in most registers. During the 20-year period, all but one register showed statistically significant changes in incidence, with rates universally increasing. When estimated separately for the first and second halves of the period, the median rates of increase were similar: 3.4% per annum and 3.3% per annum, respectively. However, rates of increase differed significantly between the first half and the second half for nine of the 21 registers with adequate coverage of both periods; five registers showed significantly higher rates of increase in the first half, and four significantly higher rates in the second half.

CONCLUSIONS/INTERPRETATION

The incidence rate of childhood type 1 diabetes continues to rise across Europe by an average of approximately 3-4% per annum, but the increase is not necessarily uniform, showing periods of less rapid and more rapid increase in incidence in some registers. This pattern of change suggests that important risk exposures differ over time in different European countries. Further time trend analysis and comparison of the patterns in defined regions is warranted.

Worth the wait: type 1 diabetes prospective birth cohort studies enter adolescence

Autoantibodies to islet cell proteins currently provide the only reliable indication that the process leading to type 1 diabetes has started. The period from the first detection of islet autoantibodies to clinical onset of diabetes can last months or years. Longitudinal birth cohort family studies give crucial information concerning the natural history of islet autoimmunity and have already shown that islet autoantibodies, which precede diabetes development, often appear in early infancy. In this issue of Diabetologia, Ziegler et al (DOI: 10.1007/s00125-012-2472-x ) and Parikka et al (DOI: 10.1007/s00125-012-2523-3 ) report findings from their birth cohort studies after numerous children have entered adolescence, allowing a more complete picture of islet autoimmunity in childhood to be revealed. Both groups are in accord that, between 6 months and 3 years of age, there is an explosion of islet autoimmunity in susceptible children and that the great majority (approximately 80%) of genetically at-risk children who present with diabetes before adolescence develop islet autoimmunity at this young age. These findings emphasise the importance of early life events in disease pathogenesis and have major implications for efforts aimed at preventing type 1 diabetes.

'Insulin autoantibody affinity measurement using a single concentration of unlabelled insulin competitor discriminates risk in relatives of patients with type 1 diabetes

Development of high-risk combinations of multiple islet autoantibodies and type 1 diabetes is associated with high-affinity insulin autoantibodies (IAA), but IAA affinity measurements require large serum volumes. We therefore investigated whether a simplified method of IAA affinity measurement using a low concentration of unlabelled insulin (ULI) competitor discriminated between moderate-high- and low-affinity IAA and identified individuals at highest risk of disease. Samples were assayed by radiobinding microassay using high (4·0 × 10(-5) mol/l) and low (7 × 10(-9) mol/l) ULI concentrations for competitive displacement in three cohorts of IAA-positive individuals; (1) 68 patients with newly-diagnosed type 1 diabetes; (2) 40 healthy schoolchildren; and (3) 114 relatives of patients with type 1 diabetes followed prospectively for disease development (median follow-up 13 years). IAA results obtained with low ULI were expressed as a percentage of those obtained with high ULI and this was used to classify samples as low or moderate-high affinity (0-50% and >50%, respectively). Sixty-eight patient samples were positive with high and 67 (99%) with low ULI. Forty schoolchildren were IAA-positive with high and 22 (55%) with low ULI (P < 0·001). Of the relatives, 113 were positive with high and 83 (73%) with low ULI (P < 0·001). In relatives, moderate-high affinity IAA were associated with multiple islet antibodies (P < 0·001) and greater diabetes risk than low affinity IAA (P < 0·001). A single low concentration of ULI competitor can act as a surrogate for complex IAA affinity measurements and identifies those IAA-positive relatives at highest risk of disease progression.

An increased frequency of NK cell receptor and HLA-C group 1 combinations in early-onset type 1 diabetes

AIMS/HYPOTHESIS

Natural killer (NK) cells serve as primary immune surveillance and are partially regulated by combinations of killer immunoglobulin-like receptor (KIR) genes and their HLA class I ligands. Alterations in NK cell activity have been associated with type 1 diabetes. The aim of this study was to determine whether KIR-HLA class I gene frequency: (1) is altered in a current population with type 1 diabetes compared with healthy controls; and (2) has changed over the half century in which the incidence of type 1 diabetes has increased rapidly.

METHODS

KIR-HLA class I gene frequencies were compared in 551 individuals diagnosed with type 1 diabetes ≤ 15 years of age (394 in a current cohort and 157 from the historical 'Golden Years' cohort) and 168 healthy controls. The overall balance of activation and inhibition was analysed using KIR-HLA genotype models.

RESULTS

Children with type 1 diabetes who were positive for KIR2DS2/KIR2DL2 and KIR2DL3 were more often homozygous for HLA-C group 1 and this effect was strongest in children diagnosed with diabetes before the age of 5 years (p = 0.003, corrected p [p (corr)] = 0.012) and (p = 0.001, p (corr) = 0.004), respectively. Children with type 1 diabetes have fewer inhibitory KIRs with their corresponding ligands compared with healthy controls (p = 1.9 × 10(-4)). This pattern of NK activation has not changed significantly in individuals with type 1 diabetes over the last half century.

CONCLUSIONS/INTERPRETATION

Activating combinations of KIR-HLA genes are more frequent in young children with type 1 diabetes diagnosed in the first 5 years of life, suggesting that NK cell responses may be altered in this group.

Prevention of type 1 diabetes

INTRODUCTION/BACKGROUND

Type 1 diabetes is a chronic autoimmune condition characterized by destruction of insulin-producing β cells within the pancreatic islets. It is associated with considerable morbidity and mortality. Incidence levels are rising worldwide.

SOURCES OF DATA

Pubmed search (Nov 2010) using keywords: Type 1 diabetes, prevention, trials, immunotherapy.

AREAS OF AGREEMENT

The causes of disease are multifactorial with genetic and environmental factors playing a part. There is a long pre-clinical period before the onset of overt symptoms, which may be amenable to therapeutic intervention to prevent disease.

AREAS OF CONTROVERSY

The exact nature of causative environmental factors is unknown and much debated. Immunotherapeutic intervention may therefore represent the best option for disease prevention.

GROWING POINTS

Enhancement of 'regulatory' immune mechanisms currently shows the most promise as an approach to disease prevention.

AREAS TIMELY FOR DEVELOPING RESEARCH

Clinical trials of early immunotherapeutic intervention may be the answer to disease prevention.

Diabetes Antibody Standardization Program: evaluation of assays for insulin autoantibodies

AIMS/HYPOTHESIS

Insulin autoantibodies (IAA) are important in type 1 diabetes risk assessment. However, their determination varies more between laboratories than other diabetes autoantibodies. The Diabetes Antibody Standardization Program (DASP) aims to improve and standardise measurement of autoantibodies associated with type 1 diabetes. We report the results of measurement of IAA from DASP workshops in 2002, 2003 and 2005.

METHODS

Up to 32 laboratories in 14 countries participated in each workshop. Aliquots of coded sera from 50 patients with newly diagnosed type 1 diabetes and 100 blood donor controls were circulated to participating laboratories. Reported results were analysed using receiver operator characteristic (ROC) curves. We compared concordance of antibody levels by ranking, IAA and insulin antibody (IA) indices and units derived from an IA standard curve.

RESULTS

In all three workshops IAA assay performance had improved compared with DASP 2000. The median area under the ROC curve was 0.73 in DASP 2002, 0.78 in 2003 and 0.80 in 2005 (p = 0.0012), and median laboratory-assigned sensitivity was 26% in 2002, 36% in 2003 and 45% in 2005 (p < 0.0001). There was, however, marked variation between assays. The range of AUC was 0.36-0.91 and that of laboratory-assigned sensitivity was 22-57%. Concordance of ranking of patient serum samples was related to AUC (p < 0.001). Using an index related to common IAA and IA-positive or -negative control sera improved the concordance between assays (p < 0.0001).

CONCLUSIONS/INTERPRETATION

The overall performance of IAA assays has improved but there is still wide variation between laboratories. Concordance between assays would be improved by the use of a common reference reagent.

Strategies to prevent type 1 diabetes

Type 1 diabetes is a chronic autoimmune condition resulting from T cell-mediated destruction of the insulin-producing cells in the islets of Langerhans. Its primary cause remains unknown, but it has been established that the clinical presentation is preceded by a long prodrome. This enables individuals at high risk of disease to be identified and offers the possibility of intervention to prevent clinical disease. Many groups are working in this field, concentrating on manipulation of environmental exposures that are potential triggers of autoimmunity and on immunomodulation strategies that aim to prevent destruction of beta-cells. Some interventions have shown promising results in early trials, but effective disease prevention remains elusive. This article reviews current progress in the field.

Diabetes mellitus among young adults in Sri Lanka--role of GAD antibodies in classification and treatment: the Sri Lanka Young Diabetes study

AIMS/HYPOTHESIS

Diabetes mellitus is increasing among young adult South Asians. The aim of this study was to determine the prevalence and phenotypic characteristics of diabetes subtypes based on GAD65 autoantibody (GADA) status in those with young adult-onset diabetes in Sri Lanka.

METHODS

Clinical, metabolic and GADA data were available for 992 consecutively recruited individuals with diabetes aged < or =45 years (age at diagnosis 16-40 years). Participants were classified according to the following definitions: type 1 diabetes, insulin-dependent <6 months from diagnosis; latent autoimmune diabetes in adults (LADA), GADA-positive, age > or =30 years and insulin-independent > or =6 months from diagnosis; type 2 diabetes, GADA-negative and insulin-independent > or =6 months from diagnosis.

RESULTS

The median (interquartile range) age at diagnosis and diabetes duration were 33.0 (29.0-36.1) and 4.0 (1.1-7.1) years, respectively; 42.1% were male. GADA positivity was seen in 5.4% of participants (n = 54) and GADA levels negatively correlated with age at diagnosis (p < 0.0001), BMI (p < 0.0001) and time to insulin requirement (p = 0.006). Type 1 diabetes, type 2 diabetes and LADA were present in 7.0%, 89.7% and 2.6%, respectively. The remaining 0.7% of the participants were GADA-positive, insulin independent > or =6 months from diagnosis and were diagnosed at age <30 years. The metabolic syndrome and homeostasis model assessment of beta cell function (HOMA %B) were lowest in GADA-positive type 1 diabetes and increased progressively in latent autoimmune diabetes, GADA-negative type 1 diabetes and type 2 diabetes. Among those requiring insulin, 69.2% had fasting C-peptide levels in the lowest quartile, whereas only 19.5% were GADA-positive (p < 0.0001).

CONCLUSIONS/INTERPRETATION

The prevalence of GADA-positive autoimmune diabetes is low among individuals with young adult-onset diabetes in Sri Lanka. Young-onset diabetic phenotypes appear as a continuum from autoimmune type 1 diabetes to type 2 diabetes.

Autoantibodies to islet antigen-2 are associated with HLA-DRB1*07 and DRB1*09 haplotypes as well as DRB1*04 at onset of type 1 diabetes: the possible role of HLA-DQA in autoimmunity to IA-2

AIMS/HYPOTHESIS

To further our understanding of antigen presentation by HLA class II molecules, we have examined the influence of HLA class II genotype on expression of autoantibodies to islet antigen-2 (IA-2A).

METHODS

HLA class II genotype and IA-2A were determined within 3 months of diagnosis in 618 patients with type 1 diabetes (median age 11 years [range 0.7-20.9]). Antibodies to the juxtamembrane region of IA-2 were measured by a radiobinding assay in 481 of 484 IA-2A-positive patients.

RESULTS

IA-2A prevalence was highest in patients carrying at least one HLA-DRB1*04-DQA1*0301 (385 of 450; 86%), DRB1*07-DQA1*(0201 or 0301) (58 of 64; 91%) or DRB1*09-DQA1*0301 haplotype (18 of 19; 95%). Multiple regression showed that IA-2A were strongly associated with the number of these haplotypes carried; only 69 of 132 (52%) patients carrying none of these haplotypes had IA-2A, compared with 322 of 391 (82%) patients with one and 93 of 95 (98%) with two of these haplotypes (p < 0.001). IA-2 juxtamembrane antibodies were less frequent in IA-2A-positive patients with one (35%) or two (36%) DRB1*03-DQB1*02 or DRB1*07-DQB1*02 haplotypes than in those negative for these haplotypes (52%) (p = 0.002), but showed an independent positive association with IA-2A level (p < 0.001).

CONCLUSIONS/INTERPRETATION

HLA class II alleles strongly influence the prevalence of IA-2A. The high IA-2A prevalence in patients carrying DRB1*04, DRB1*07 and DRB1*09 alleles in linkage disequilibrium with DQA1*0301 or the closely related DQA1*0201 suggests the humoral response to IA-2 may be driven by HLA-DQA1 genes.

Diabetes Antibody Standardization Program: evaluation of assays for autoantibodies to glutamic acid decarboxylase and islet antigen-2

AIMS/HYPOTHESIS

Islet autoantibodies are important in diabetes classification and risk assessment, and as endpoints in observational studies. The Diabetes Autoantibody Standardization Program (DASP) aims to improve and standardise measurement of autoantibodies associated with type 1 diabetes. We report results for glutamic acid decarboxylase autoantibodies (GADA) and islet antigen-2 autoantibodies (IA-2A) from three DASP workshops (2002--2005).

METHODS

Up to 60 laboratories in 18 countries participated in each workshop. Participants received coded serum aliquots from 50 patients with newly diagnosed type 1 diabetes (median age 18 years, range 9-35 years) and 100 blood donor controls. Results were analysed using receiver operator characteristic (ROC) curves with sensitivity adjusted to 95% specificity in workshop controls.

RESULTS

GADA assays performed well in all three workshops (median area under the ROC curve [AUC] 0.94; interquartile range 0.91-0.95) and performance was similar to DASP 2000. Performance of IA-2A assays improved over the workshop programme. Median AUC was 0.81 (interquartile range 0.79-0.83) in DASP 2002, 0.82 (interquartile range 0.78-0.84) in 2003, and 0.85 (interquartile range 0.82-0.87) in 2005 (p < 0.0001). Performance of GADA ELISA improved between 2002 and 2005, and, in DASP 2005, achieved higher median AUC and adjusted sensitivity than RIA. IA-2A ELISA improved and, in DASP 2005, achieved AUCs equivalent to in-house RIA. Assays using IA-2ic or full length IA-2 clones were more sensitive than those using IA-2bdc, with higher AUC (p = 0.004).

CONCLUSIONS/INTERPRETATION

GADA and IA-2A assays perform well in discriminating health and disease. The workshop format highlights systematic differences related to assay method and allows full evaluation of novel methods. The programme of autoantibody workshops in type 1 diabetes provides a model for other autoimmune diseases.

Autoantibodies to IA-2beta improve diabetes risk assessment in high-risk relatives

AIMS/HYPOTHESIS

The aim of this study was to evaluate the prognostic significance of autoantibodies to IA-2beta (IA2betaA) in a large, well-characterised population of islet cell antibody (ICA)-positive relatives followed for 5 years in the European Nicotinamide Diabetes Intervention Trial.

METHODS

Autoantibodies to insulin (IAA), glutamate decarboxylase (GADA) and IA-2 (IA2A) were measured in 549 participants at study entry, and IA2A-positive samples tested for IA2betaA. First-phase insulin response (FPIR) and oral glucose tolerance were determined at baseline.

RESULTS

Of 212 ICA/IA2A-positive participants (median age 12.1 years; 57% male), 113 developed diabetes (5 year cumulative risk 56%), and 148 were also GADA-positive and IAA-positive (4Ab-positive). IA2betaA were detected in 137 (65%) ICA/IA2A-positive participants and were associated with an increased 5 year diabetes risk (IA2betaA-positive 65 vs 39% in IA2betaA-negative, p=0.0002). The effect was most marked in 4Ab-positive relatives (72% vs 52%, p=0.003). Metabolic testing further refined risk assessment. Among 101 4Ab-positive relatives with IA2betaA, the 5 year risk was 94% in those with a low FPIR (vs 50% in those with a normal FPIR, p<0.0001), and 95% in those with impaired glucose tolerance (IGT) (vs 66% in those with normal glucose tolerance, p<0.0001). The median time to diagnosis of 4Ab/IA2betaA-positive participants with a low FPIR was 1.5 years. Multivariate analysis confirmed IA2betaA status, antibody number, young age, FPIR and IGT as independent determinants of risk.

CONCLUSIONS/INTERPRETATION

IA2betaA are associated with a very high risk of diabetes in ICA/IA2A-positive relatives. Testing for IA2A/IA2betaA compares favourably with the IVGTT in identifying a subgroup of autoantibody-positive relatives at increased risk. IA2betaA determination should be added to screening protocols of future intervention trials.

GAD autoantibodies and epitope reactivities persist after diagnosis in latent autoimmune diabetes in adults but do not predict disease progression: UKPDS 77

AIMS/HYPOTHESIS

Latent autoimmune diabetes in adults (LADA) is a slowly progressive form of autoimmune diabetes, with autoantibodies to islet proteins developing in older patients who have no immediate requirement for insulin therapy. Markers of its clinical course are uncharacterised. The aim of this study was to determine whether persistence of, or changes in, GAD65 autoantibodies (GADAs) in the LADA patients who participated in the United Kingdom Prospective Diabetes Study (UKPDS) were associated with disease progression or insulin requirement.

METHODS

GADA levels and their relative epitope reactivities to N-terminal, middle and C-terminal regions of human GAD65 were determined in 242 UKPDS patients who were GADA-positive at diagnosis; samples taken after 0.5, 3 and 6 years of follow-up were tested using a radiobinding assay. Comparisons were made of GADA status with clinical details and disease progression assessed by the requirement for intensified glucose-lowering therapy.

RESULTS

GADA levels fluctuated between 0.5 and 6 years but persisted in 225 of 242 patients. No association of GADA levels with disease progression or insulin requirement was observed. Antibody reactivity was directed to C-terminal and middle epitopes of GAD65 in >70% patients, and the N-terminal in <9%. There were no changes in epitope reactivity pattern over the 6 year follow-up period, nor any association between epitope reactivity and insulin requirement.

CONCLUSIONS/INTERPRETATION

GADAs persist for 6 years after diagnosis of LADA, but levels and reactivity to different GAD65 epitopes are not associated with disease progression.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

An association analysis of the HLA gene region in latent autoimmune diabetes in adults

AIMS/HYPOTHESIS

Pathophysiological similarities between latent autoimmune diabetes in adults (LADA) and type 1 diabetes indicate an overlap in genetic susceptibility. HLA-DRB1 and HLA-DQB1 are major susceptibility genes for type 1 diabetes but studies of these genes in LADA have been limited. Our aim was to define patterns of HLA-encoded susceptibility/protection in a large, well characterised LADA cohort, and to establish association with disease and age at diagnosis.

MATERIALS AND METHODS

Patients with LADA (n = 387, including 211 patients from the UK Prospective Diabetes Study) and non-diabetic control subjects (n = 327) were of British/Irish European origin. The HLA-DRB1 and -DQB1 genes were genotyped by sequence-specific PCR.

RESULTS

As in type 1 diabetes mellitus, DRB1 0301_DQB1 0201 (odds ratio [OR] = 3.08, 95% CI 2.32-4.12, p = 1.2 x 10(-16)) and DRB1 0401_DQB1 0302 (OR = 2.57, 95% CI 1.80-3.73, p = 4.5 x 10(-8)) were the main susceptibility haplotypes in LADA, and DRB1 1501_DQB1 0602 was protective (OR = 0.21, 95% CI 0.13-0.34, p = 4.2 x 10(-13)). Differential susceptibility was conferred by DR4 subtypes: DRB1 0401 was predisposing (OR = 1.79, 95% CI 1.35-2.38, p = 2.7 x 10(-5)) whereas DRB1 0403 was protective (OR = 0.37, 95% CI 0.13-0.97, p = 0.033). The highest-risk genotypes were DRB1 0301/DRB1 0401 and DQB1 0201/DQB1 0302 (OR = 5.14, 95% CI 2.68-10.69, p = 1.3 x 10(-8); and OR = 6.88, 95% CI 3.54-14.68, p = 1.2 x 10(-11), respectively). These genotypes and those containing DRB1 0401 and DQB1 0302 associated with a younger age at diagnosis in LADA, whereas genotypes containing DRB1 1501 and DQB1 0602 associated with an older age at diagnosis.

CONCLUSIONS/INTERPRETATION

Patterns of susceptibility at the HLA-DRB1 and HLA-DQB1 loci in LADA are similar to those reported for type 1 diabetes, supporting the hypothesis that autoimmune diabetes occurring in adults is an age-related extension of the pathophysiological process presenting as childhood-onset type 1 diabetes.

Type 1 diabetes risk assessment: improvement by follow-up measurements in young islet autoantibody-positive relatives

AIMS/HYPOTHESIS

Combinations of autoantibody characteristics, including antibody number, titre, subclass and epitope have been shown to stratify type 1 diabetes risk in islet autoantibody-positive relatives. The aim of this study was to determine whether autoantibody characteristics change over time, the nature of such changes, and their implications for the development of diabetes.

METHODS

Five-hundred and thirteen follow-up samples from 141 islet autoantibody-positive first-degree relatives were tested for islet autoantibody titre, IgG subclass, and GAD and IA-2 antibody epitope. All samples were categorised according to four risk stratification models. Relatives had a median follow-up of 6.8 years and 48 developed diabetes during follow-up. Survival analysis was used to determine the probability of change in risk category and of progression to diabetes.

RESULTS

For each stratification model, the majority of relatives (71-81%) remained in the same risk category throughout follow-up. In the remainder, changes occurred both from lower to higher and from higher to lower risk categories. For all four models, relatives aged < 15 years were more likely to change risk category than those aged >15 years (0.001 < p < 0.03). Relatives whose autoantibody status changed from low- to high-risk categories had a higher risk of diabetes than relatives who remained in low-risk categories, and inclusion of autoantibody status during follow-up improved diabetes risk stratification in Cox proportional hazards models (p < 0.001).

CONCLUSIONS/INTERPRETATION

Changes in islet autoantibodies are relevant to pathogenesis, and are likely to signal alterations in the disease process. Detection of changes through follow-up measurement will improve diabetes risk stratification, particularly in young individuals.

GAD antibodies in probands and their relatives in a cohort clinically selected for Type 2 diabetes

AIMS

A subset of patients who present as if they have Type 2 diabetes have positive pancreatic autoantibodies, and have been referred to as having latent autoimmune diabetes in adults (LADA). We assessed the prevalence and clinical characteristics of patients with glutamic acid decarboxylase antibodies (GADA) in a cohort clinically selected for Type 2 diabetes and determined the presence of diabetes and GADA in their first-degree relatives.

METHODS

GADA were measured in 2059 subjects, not known to be related, and clinically selected as having Type 2 diabetes for genetic studies. Clinical characteristics were compared in GADA positive and GADA negative subjects. Diabetes and GAD antibody status were compared in 208 first-degree relatives of GADA positive and GADA negative probands.

RESULTS

Of the subjects, 136 (7%) were GADA positive. Compared with the GADA negative subjects, they were slimmer (P < 0.001), diagnosed at a younger age (P = 0.011) and progressed to insulin faster (P < 0.001). Thirty-three per cent of GADA positive subjects had a first-degree relative with diabetes compared with 42% of GADA negative subjects (P = 0.034). The overall prevalence of GADA was similar in the first-degree relatives of GADA positive and GADA negative probands (4 v 5%), and 19 of 22 (86%) diabetic relatives of GADA positive probands were GADA negative.

CONCLUSION

Despite clinically selecting a Type 2 diabetes cohort, 7% were GADA positive with an altered phenotype. These GADA positive patients had a strong family history of non-autoimmune diabetes. This suggests that, in this subgroup of patients, autoimmune pancreatic beta-cell destruction occurs on a background of Type 2 diabetes genetic susceptibility.

Progression to type 1 diabetes in islet cell antibody-positive relatives in the European Nicotinamide Diabetes Intervention Trial: the role of additional immune, genetic and metabolic markers of risk

AIMS/HYPOTHESIS

To examine the role of additional immune, genetic and metabolic risk markers in determining risk of diabetes in islet cell antibody (ICA)-positive individuals with a family history of type 1 diabetes recruited into the European Nicotinamide Diabetes Intervention Trial.

METHODS

Five hundred and forty-nine first-degree relatives with confirmed ICA levels > or =20 Juvenile Diabetes Foundation units (mean age 15.9 years; interquartile range 10.4-33.7 years) were recruited from 20 countries. OGTTs and IVGTTs were performed at baseline, antibodies to glutamate decarboxylase (GADA), protein tyrosine phosphatase (IA-2A) and insulin (IAA) were determined by RIA, and HLA class II genotyping was performed by PCR of sequence-specific oligonucleotides.

RESULTS

One hundred and fifty-nine participants developed diabetes within 5 years. Univariate analysis showed that the cumulative risk of development of diabetes within 5 years varied according to age, relationship to the proband, positivity for IAA, IA-2A and GADA, number and combination of islet antibodies, HLA class II genotype, baseline glucose tolerance, and first-phase insulin secretion, but not gender or incidence of childhood type 1 diabetes in the background population. Children aged < or =10 years had a 59% risk of diabetes within 5 years, compared with 11% in those > or =25 years (p<0.0001). Using multivariate analysis, independent determinants were age, first-phase insulin response, baseline glucose tolerance and number of additional antibody markers, but not antibody type or genotype. Individuals <25 years with two or more additional antibodies at baseline had a 62% risk of diabetes within 5 years and these combined criteria identified 81% of the cases in the whole cohort.

CONCLUSIONS/INTERPRETATION

We suggest that screening and recruitment for future intervention trials should be limited to family members aged <25 years, and should be based on islet autoantibodies alone.

Continuing metformin when starting insulin in patients with Type 2 diabetes: a double-blind randomized placebo-controlled trial

AIMS

To test the effect of continuing metformin on weight gain and glycaemic control in patients with poorly controlled Type 2 diabetes who need to start insulin.

METHODS

Patients with Type 2 diabetes on maximum tolerated oral agents referred for insulin conversion were recruited from hospital diabetes clinics into a double-blind randomized placebo-controlled trial. The 183 participants received metformin or placebo, titrated up to 2 g a day or maximum tolerated dose, with insulin started according to local practice. The main outcome measures were weight change over 12 months, HbA1c, insulin dose, frequency of hypoglycaemia, treatment satisfaction, and well-being.

RESULTS

Over 12 months, metformin was associated with less weight gain than placebo [mean 6.1 kg vs. 7.6 kg; adjusted difference 1.5 kg (95% confidence interval 0.2-2.9); P=0.02], a greater reduction in HbA1c[1.5% vs. 1.3%; adjusted difference 0.5% (0.1-0.9); P=0.02] and a lower insulin requirement [62 units vs. 86; adjusted difference 25 units (15-34); P<0.001], but also more hypoglycaemia [relative risk of any episode 1.24 (1.02-1.1); P=0.03]. Treatment satisfaction improved more in patients on metformin than on placebo (P<0.001), as did the positive well-being score (P=0.02).

CONCLUSIONS

Metformin decreases weight gain, lowers insulin requirement, and improves glycaemic control, and should be continued in patients with Type 2 diabetes who transfer to insulin.

Mortality of South Asian patients with insulin-treated diabetes mellitus in the United Kingdom: a cohort study

AIMS

To investigate mortality in South Asian patients with insulin-treated diabetes and compare it with mortality in non South Asian patients and in the general population.

METHODS

A prospective cohort study was conducted of 828 South Asian and 27 962 non South Asian patients in the UK with insulin-treated diabetes diagnosed at ages under 50 years. The patients were followed for up to 28 years. Ethnicity was determined by analysis of names. Standardized mortality ratios (SMRs) were calculated, comparing mortality in the cohort with expectations from the mortality experience of the general population.

RESULTS

SMRs were significantly raised in both groups of patients, particularly the South Asians, and especially in women and subjects with diabetes onset at a young age. The SMRs for South Asian patients diagnosed under age 30 years were 3.9 (95% CI 2.0-6.9) in men and 10.1 (5.6-16.6) in women, and in the corresponding non South Asians were 2.7 (2.6-2.9) and 4.0 (3.6-4.3), respectively. The SMR in women was highly significantly greater in South Asians than non South Asians. The mortality in the young-onset patients was due to several causes, while that in the patients diagnosed at ages 30-49 was largely due to cardiovascular disease, which accounted for 70% of deaths in South Asian males and 73% in females.

CONCLUSIONS

South Asian patients with insulin-treated diabetes suffer an exceptionally high mortality. Clarification of the full reasons for this mortality are needed, as are measures to reduce levels of known cardiovascular disease risk factors in these patients.

European Nicotinamide Diabetes Intervention Trial (ENDIT): a randomised controlled trial of intervention before the onset of type 1 diabetes

BACKGROUND

Results of studies in animals and human beings suggest that type 1 diabetes is preventable. Nicotinamide prevents autoimmune diabetes in animal models, possibly through inhibition of the DNA repair enzyme poly-ADP-ribose polymerase and prevention of beta-cell NAD depletion. We aimed to assess whether high dose nicotinamide prevents or delays clinical onset of diabetes in people with a first-degree family history of type 1 diabetes.

METHOD

We did a randomised double-blind placebo-controlled trial of nicotinamide in 552 relatives with confirmed islet cell antibody (ICA) levels of 20 Juvenile Diabetes Federation (JDF) units or more, and a non-diabetic oral glucose tolerance test. Participants were recruited from 18 European countries, Canada, and the USA, and were randomly allocated oral modified release nicotinamide (1.2 g/m2) or placebo for 5 years. Random allocation was done with a pseudorandom number generator and we used size balanced blocks of four and stratified by age and national group. Primary outcome was development of diabetes, as defined by WHO criteria. Analysis was done on an intention-to-treat basis.

FINDINGS

There was no difference in the development of diabetes between the treatment groups. Of 159 participants who developed diabetes in the course of the trial, 82 were taking nicotinamide and 77 were on placebo. The unadjusted hazard ratio for development of diabetes was 1.07 (95% CI 0.78-1.45; p=0.69), and the hazard ratio adjusted for age-at-entry, baseline glucose tolerance, and number of islet autoantibodies detected was 1.01 (0.73-1.38; p=0.97). Of 168 (30.4%) participants who withdrew from the trial, 83 were on placebo. The number of serious adverse events did not differ between treatment groups. Nicotinamide treatment did not affect growth in children or first-phase insulin secretion.

INTERPRETATION

Large-scale controlled trials of interventions designed to prevent the onset of type 1 diabetes are feasible, but nicotinamide was ineffective at the dose we used.

Three generations of autoimmune diabetes: an extended family study

AIMS/HYPOTHESIS

One in four children with Type 1 diabetes in a population-based family study has an affected grandparent. We set out to study the clinical and immune features of diabetes in the grandparents' generation, and to examine sharing of HLA class II susceptibility haplotypes between grandparent and grandchild.

METHODS

Of 5855 grandparents in the Bart's-Oxford family study, 428 (7.3%) were known to have diabetes. Clinical data and samples were collected from 115 of 213 surviving affected grandparents and from 219 unaffected grandparents within the same families. Samples were tested for ICA and autoantibodies to GAD and IA-2, and typed for HLA-DRB1-DQA1-DQB1. Transmission of HLA class II haplotype from affected and unaffected grandparents to the diabetic proband was compared.

RESULTS

Of 115 affected grandparents studied, the median age at diagnosis was 61 years and at analysis was 73 years; 70% were diet or tablet treated and 30% were on insulin. One or more islet autoantibodies were found in 26% and 66% had one or both of the high risk HLA class II susceptibility haplotypes DRB1*03-DQA1*0501-DQB1*0201 or DRB1*04-DQA1*0301-DQB1*0302. In 79 informative families the HLA class II haplotype of the affected grandparent was transmitted to the proband more frequently than expected overall (59%, p=0.02), and in the insulin-treated subgroups (65%, p=0.03).

CONCLUSION/INTERPRETATION

A total of 7.3% of grandparents reported a clinical diagnosis of diabetes and 2.2% had features of Type 1 diabetes. Genetic susceptibility was shared between grandparents with diabetes and their affected grandchildren. Diabetes in the grandparents of children with Type 1 diabetes often has an autoimmune basis, even when it presents late in life and does not require insulin treatment.

The prevalence of insulin autoantibodies at the onset of Type 1 diabetes is higher in males than females during adolescence

AIMS/HYPOTHESIS

The incidence of Type 1 diabetes shows little sex bias up to age 15 years, but more males are diagnosed in early adult life. Humoral responses to the beta cell antigen insulin could help to reveal the mechanism underlying this difference. We therefore determined the influence of sex on the prevalence of insulin autoantibodies (IAA) at diagnosis.

METHODS

IAA were measured by radiobinding assay in 598 patients with newly diagnosed Type 1 diabetes (aged 10.5, range 0.8-20.7 years, 333 male), and analysed according to age, sex and HLA class II genotype.

RESULTS

Overall, 74% of males and 65% of females had IAA above the 97.5(th) centile of 2860 schoolchildren ( p=0.028). IAA prevalence was similar in males and females under the age of 15 (0-4 yr, 95% vs 88%; 5-9 yr, 76% vs 73%; 10-14 yr, 67% vs 58%), but male excess was seen between 15 and 21 years (66% vs. 32%, p(corr)=0.016). HLA class II genotype was available for 426 patients. IAA prevalence in DR4 homozygous patients was 87%, in DR4 heterozygous patients 72% and in DR4 negative patients 55% ( p<0.001). Multivariate analysis showed independent association of IAA with age ( p<0.001), number of DR4 alleles ( p<0.001) and male sex ( p=0.002).

CONCLUSIONS/INTERPRETATION

The prevalence of IAA in patients with newly diagnosed Type 1 diabetes is higher in males than females between 15 and 21 years of age. The lower prevalence of IAA in adolescent females implies sex-specific modulation of the autoimmune process during puberty.

Mortality from heart disease in a cohort of 23,000 patients with insulin-treated diabetes

AIMS/HYPOTHESIS

Although ischaemic heart disease is the predominant cause of mortality in older people with diabetes, age-specific mortality rates have not been published for patients with Type 1 diabetes. The Diabetes UK cohort, essentially one of patients with Type 1 diabetes, now has sufficient follow-up to report all heart disease, and specifically ischaemic heart disease, mortality rates by age.

METHODS

A cohort of 23,751 patients with insulin-treated diabetes, diagnosed under the age of 30 years and from throughout the United Kingdom, was identified during the period 1972 to 1993 and followed for mortality until December 2000. Age- and sex-specific heart disease mortality rates and standardised mortality ratios were calculated.

RESULTS

There were 1437 deaths during the follow-up, 536 from cardiovascular disease, and of those, 369 from ischaemic heart disease. At all ages the ischaemic heart disease mortality rates in the cohort were higher than in the general population. Mortality rates within the cohort were similar for men and women under the age of 40. The standardised mortality ratios were higher in women than men at all ages, and in women were 44.8 (95%CI 20.5-85.0) at ages 20-29 and 41.6 (26.7-61.9) at ages 30-39.

CONCLUSIONS/INTERPRETATION

The risk of mortality from ischaemic heart disease is exceptionally high in young adult women with Type 1 diabetes, with rates similar to those in men with Type 1 diabetes under the age of 40. These observations emphasise the need to identify and treat coronary risk factors in these young patients.

Diabetes in the parents of children with Type I diabetes

AIMS/HYPOTHESIS

Previous studies have reported an excess of Type II (non-insulin-dependent) diabetes mellitus in parents of children with Type I (insulin-dependent) diabetes mellitus. We set out to characterise the clinical and immunogenetic features of diabetes in parents of affected children, and to test the hypothesis that there is no excess of Type II diabetes within this population.

METHODS

Clinical details were collected from 3164 parents of 1641 children with Type I diabetes participating in the Bart's-Oxford study of childhood diabetes. Islet cell antibodies, antibodies to GAD and IA-2, and HLA class II genotype were determined in a subset of this group. Individuals were assigned a classification of Type I diabetes on the basis of clinical features and measurement of islet autoantibodies.

RESULTS

Of 184 parents with diabetes, 138 (75 %) were on insulin. At least one islet autoantibody was detected in 90 (59 %) of 152 parents tested, and of 116 who were HLA-typed, 23 (20 %) had the highest risk genotype HLA-DRB1(*)03-DQA1*0501-DQB1(*)0201 / DRB1*04-DQA1(*)0301-DQB1*0302. Of 46 non-insulin-treated parents, 12 had islet autoantibodies. Of all parents, 141 (4.5 %) were therefore classified as having Type I diabetes, and 31 (0.98 %) as Type II diabetes; 12 could not be classified because of missing data or samples.

CONCLUSION/INTERPRETATION

Autoimmune diabetes can present late and without immediate need for insulin treatment in parents of children with the disease. Previous studies have categorised this as Type II diabetes. Our study suggests that there is no excess of non-autoimmune diabetes in the families of children with Type I diabetes.

Islet autoantibodies, nationality and gender: a multinational screening study in first-degree relatives of patients with Type I diabetes

AIMS/HYPOTHESIS

First-degree relatives of patients with Type I (insulin-dependent) diabetes mellitus diagnosed at 20 years of age or under were screened for islet cell antibodies (ICA) in the course of recruitment to an international diabetes prevention trial. Our aim was to evaluate the influence of age, gender, proband characteristics and nationality on the prevalence of ICA and co-existence of autoantibodies to GAD, IA-2 and insulin.

METHODS

A central laboratory screened samples from 10 326 non-diabetic relatives who were aged less than 40 years, from eight European countries for ICA. Antibodies to GAD and IA-2 were measured in all samples with ICA of 10 JDF units or more.

RESULTS

Overall, 8.9 % of relatives had ICA of 10 JDF units or more, 3.8 % with ICA of 20 JDF units or more. Of 921 relatives with ICA of 10 JDF units or more, 29 % had co-existing antibodies to GAD or IA-2 or both. ICA of 10 JDF units or more were more prevalent in males (10.8 %) than females (7.3 %). ICA with GAD or IA-2 antibodies or both were also more common in males (3.4 %) than females (1.9 %) and in relatives under 20 years of age (3.5 % vs 1.5 %). Multiple regression analysis showed nationality to be a determinant of ICA of 10 JDF units or more but not of ICA of 20 JDF units or more or of ICA with co-existing islet antibodies, and confirmed the importance of age and gender as determinants of islet autoimmunity.

CONCLUSIONS/INTERPRETATION

Relatives from different European countries have similar rates of islet autoimmunity despite wide variation in the background incidence of childhood diabetes, and male excess is equally evident in all populations. The male excess of ICA and islet autoimmunity over 10 years of age reflects the higher male incidence of Type I diabetes in this age group, and suggests that boys may be more likely than girls to develop islet autoimmunity during adolescence.

The high prevalence of autoantibodies to tissue transglutaminase in first-degree relatives of patients with type 1 diabetes is not associated with islet autoimmunity

OBJECTIVE

To determine the extent of celiac autoimmunity in type 1 diabetic patients and the overlap between islet and celiac autoimmunity in their nondiabetic relatives.

RESEARCH DESIGN AND METHODS

IgA antibodies to tissue transglutaminase were determined in serum taken from 433 type 1 diabetic patients and 1,442 nondiabetic first-degree relatives. Samples with transglutaminase antibodies above the 97.5th percentile of 347 schoolchildren were also assayed for IgA anti-endomysial antibodies (EMAs). Markers of islet autoimmunity (islet cell antibodies and autoantibodies to insulin, glutamate decarboxylase. and protein tyrosine phosphatase IA-2) had previously been measured in all relatives.

RESULTS

In the absence of known celiac disease, the prevalence of transglutaminase antibody levels above the 97.5th percentile of the schoolchildren was 13.4% in diabetic patients and 7.0% in nondiabetic relatives. ENMAs were found in addition to transglutaminase antibodies in 2.6% of probands and in 1.9% of first-degree relatives, but none of the schoolchildren. Transglutaminase antibodies were found to persist in 10 of 30 patients and in 30 of 59 relatives with follow-up samples taken at least 2 years after the initial sample. Of 186 nondiabetic relatives with islet autoantibodies, only 10 also had transglutaminase antibodies.

CONCLUSIONS

We found a high prevalence of celiac autoimmunity in patients and first-degree relatives of children with type 1 diabetes, but we found limited overlap between islet and celiac autoimmunity in nondiabetic relatives. The high prevalence of celiac autoimmunity may be explained by shared genetic susceptibility and identifies a population within which screening for the disease may be justified.

Update on major trials for the prevention of type 1 diabetes mellitus: the American Diabetes Prevention Trial (DPT-1) and the European Nicotinamide Diabetes Intervention Trial (ENDIT)

The general population risk of developing type 1 diabetes mellitus (DM), 1/300, is magnified 15-20 fold in first-degree relatives of affected individuals. Because a combination of immunologic, metabolic, and genetic markers can be used to predict the disease, multicenter prevention trials in the US (DPT-1) and Europe (ENDIT) were initiated in relatives. In the DPT-1 over 80,000 relatives under 45 years of age will be screened for ICA and then 'staged' to assess risk. High-risk subjects (>50% over 5 yr) are randomized either to 4 days intravenous insulin infusion annually followed by b.i.d. low doses of subcutaneous ultralente insulin, or to close observation. To date (September 2000), 331/340 (97%) high-risk subjects have been enrolled with the intention of detecting a 35% decrease in disease over 5 years (80% power). 280/490 (57%) of intermediate risk subjects (25-50% over 5 yr) have been randomized to oral insulin or placebo. A 50% treatment difference is sought. Anticipated enrolment for the high-risk arm will be completed by year 2001, and by 2003 for the oral arm. The ENDIT study will prospectively address whether nicotinamide will reduce the rate of progression to DM in relatives. 40,000 first-degree relatives (5-40 yr) have been screened with 552 subjects (ICA titers > or = 20 JDF U) randomized to nicotinamide or placebo. This study is designed with 90% power to detect a 35% reduction in disease (placebo group estimated at 40% risk over 5 years). Analysis of data is expected in 2003.

A comparison of the prevalence of islet autoantibodies in children from two countries with differing incidence of diabetes

AIMS/HYPOTHESIS

To examine the prevalence of sub-: clinical islet autoimmunity in children from two countries with a twofold to threefold difference in incidence of childhood Type I (insulin-dependent) diabetes mellitus.

METHODS

Sera were collected from 2,860 English and 3,053 Lithuanian non-diabetic schoolchildren according to the same protocol. Occult diabetes was excluded by blood glucose measurement. Antibodies to GAD and the protein tyrosine phosphatase IA-2 were measured with standardised radiobinding assays in a single laboratory. Islet cell antibodies and insulin autoantibodies were additionally measured in all samples with GAD and/or IA-2 antibody levels above the 97.5th centile of the English schoolchildren.

RESULTS

Of Lithuanian schoolchildren 2.7 % had GAD antibodies above the 97.5th centile of the English schoolchildren but only 0.2 % had antibodies to IA-2 above this threshold (p < 0.001). Islet cell and/ or insulin autoantibodies above the 97.5th centile were found in 22 Lithuanian and 16 English schoolchildren and the overall prevalence of two or more antibodies on or above the 97.5th centile was similar [0.7 % (0.5-1.1) vs 0.6 % (0.4-1.0)] in the two cohorts.

CONCLUSION/INTERPRETATION

The prevalence of multiple antibody markers was similar in the cohorts from the two populations, despite the two to three-fold difference in incidence of diabetes. The unexpectedly high prevalence of subclinical islet autoimmunity suggests that the incidence of diabetes in Lithuania is likely to increase in the near future.

HLA class II typing of whole genome amplified mouth swab DNA

Postal collection of mouth swabs provides a cheap and convenient means of DNA sampling but hitherto has not provided sufficient genetic material for HLA typing by polymerase chain reaction using sequence-specific primers (PCR-SSP). This study examined the feasibility of collecting mouth swabs from a test population by post, amplifying the DNA by whole genome amplification and genotyping for selected HLA class II alleles. We optimised a strategy for whole genome amplification or primer extension preamplification using a random 15 base pair primer which resulted in a 1,000-fold increase in DNA template. The amplified DNA was of sufficient quality for analysis of selected HLA Class II alleles by PCR-SSP and PCR using sequence-specific oligonucleotide probes. To test the reliability of our data, blood DNA from 30 individuals in 10 families, previously tested for all DRB1 alleles in a routine diagnostic laboratory, was then tested in our laboratory for DRB1 *03 and *04 following whole genome amplification. Further whole genome amplified product from another 10 families was tested for DRB1 *03, *04 in our laboratory and then tested for all DRB1 alleles in a routine diagnostic laboratory. One repeat typing was required to achieve 100% concordance between laboratories. Amplification of whole genome amplified DNA by PCR-SSP was then extended successfully to low-resolution HLA DRB1, DQA1, DQB1 and DPB1 typing. Mouth swab collection by post, followed by whole genome amplification of DNA provides an effective strategy for genetic analysis of large cohorts. We have optimised conditions for HLA class II typing on whole genome amplified DNA collected by mouth swab, but this method could potentially be applied to low concentrations of DNA from other sources.

Safety of high-dose nicotinamide: a review

Nicotinamide, the amide derivative of nicotinic acid, has over the past forty years been given at high doses for a variety of therapeutic applications. It is currently in trial as a potential means of preventing the onset of Type I (insulin-dependent) diabetes mellitus in high-risk, first-degree relatives. Nicotinamide is for regulatory purposes classed as a food additive rather than a drug and has not therefore required the formal safety evaluation normally expected of a new therapy. Because the safety of treatment with megadoses of vitamins cannot be assumed, a full literature review has been undertaken. The therapeutic index of nicotinamide is wide but at very high doses reversible hepatotoxicity has been reported in animals and humans. Minor abnormalities of liver enzymes can infrequently occur at the doses used for diabetes prevention. There is no evidence of teratogenicity from animal studies and nicotinamide is not in itself oncogenic; at very high doses it does however potentiate islet tumour formation in rats treated with streptozotocin or alloxan. There is no evidence of oncogenicity in man. Growth inhibition can occur in rats but growth in children is unaffected. Studies of its effects on glucose kinetics and insulin sensitivity are inconsistent but minor degrees of insulin resistance have been reported. The drug is well tolerated, especially in recent studies which have used relatively pure preparations of the vitamin. Experience to date therefore suggests that the ratio of risk to benefit of long-term nicotinamide treatment would be highly favourable, should the drug prove efficacious in diabetes prevention. High-dose nicotinamide should still, however, be considered as a drug with toxic potential at adult doses in excess of 3 gm/day and unsupervised use should be discouraged.

Influence of maternal age at delivery and birth order on risk of type 1 diabetes in childhood: prospective population based family study. Bart's-Oxford Family Study Group

OBJECTIVES

To examine the influence of parental age at delivery and birth order on subsequent risk of childhood diabetes.

DESIGN

Prospective population based family study.

SETTING

Area formerly administered by the Oxford Regional Health Authority.

PARTICIPANTS

1375 families in which one child or more had diabetes. Of 3221 offspring, 1431 had diabetes (median age at diagnosis 10.5 years, range 0.4-28.5) and 1790 remained non-diabetic at a median age of 16. 1 years.

MAIN OUTCOME MEASURES

Disease free survival and hazard ratios for the development of type 1 diabetes in all offspring, assessed by Cox proportional hazard regression.

RESULTS

Maternal age at delivery was strongly related to risk of type 1 diabetes in the offspring; risk increased by 25% (95% confidence interval 17% to 34%) for each five year band of maternal age, so that maternal age at delivery of 45 years or more was associated with a relative risk of 3.11 (2.07 to 4.66) compared with a maternal age of less than 20 years. Paternal age was also associated with a 9% (3% to 16%) increase for each five year increase in paternal age. The relative risk of diabetes, adjusted for parental age at delivery and sex of offspring, decreased with increasing birth order; the overall effect was a 15% risk reduction (10% to 21%) per child born.

CONCLUSIONS

A strong association was found between increasing maternal age at delivery and risk of diabetes in the child. Risk was highest in firstborn children and decreased progressively with higher birth order. The fetal environment seems to have a strong influence on risk of type 1 diabetes in the child. The increase in maternal age at delivery in the United Kingdom over the past two decades could partly account for the increase in incidence of childhood diabetes over this period.

Soluble L-selectin levels in type I diabetes mellitus: a surrogate marker for disease activity?

L-selectin (CD62L) is a cell adhesion molecule which plays a key role in the initiation of leucocyte migration from blood vessels to sites of local inflammation. The aim of this study was to investigate T-lymphocyte expression of CD62L antigen and serum levels of soluble L-selectin (sL-selectin) in subjects with clinical and preclinical type I diabetes to determine whether they could provide surrogate markers for disease activity. CD62L selectin expression on memory T lymphocytes was studied by cytometric analysis in 22 patients with newly diagnosed type I diabetes, 20 first-degree relatives of patients with type I diabetes, 14 patients with Graves' disease, and 22 healthy controls. sL-selectin levels were measured by enzyme-linked immunosorbent assay (ELISA) in enlarged groups of subjects in these categories, as well as in patients with long-standing type I diabetes, treated Graves' disease and type II (non-insulin dependent) diabetes. L-selectin levels were also related to islet autoantibodies, human leucocyte antigen (HLA) genotype and L-selectin T668C gene polymorphisms. L-selectin expression on memory T lymphocytes was reduced in newly diagnosed diabetes and islet autoantibody positive siblings compared with controls. sL-selectin levels were significantly raised in newly diagnosed type I diabetes compared with controls, with intermediate levels in family members, both with and without islet autoantibodies, and in long-standing type I diabetes. Levels were also raised in patients with untreated Graves' disease. Patients with type II diabetes had sL-selectin levels which did not differ from controls. sL-selectin levels correlated with the presence of diabetes-associated HLA alleles in both family members and controls; levels also fell with increasing age in family members. Multiple regression analysis showed that HLA genotype and age were independent determinants of sL-selectin levels. sL-selectin levels are raised at the time of diagnosis of type I diabetes and Graves' disease and appear to be modulated by disease activity, but levels are determined predominantly by HLA-associated genetic susceptibility and age. sL-selectin may provide a late marker of autoimmune destruction of islets and sequential measurement may be useful in monitoring disease activity and the effect of interventions preceding type I diabetes.

Progression to diabetes in relatives with islet autoantibodies. Is it inevitable?

OBJECTIVE

A large cohort of family members with islet cell antibodies (ICA) > or = 20 Juvenile Diabetes Foundation units (JDF U) was examined to determine whether there was a subgroup at low risk of progression to diabetes; whether risk of progression changed over time; and whether rate of progression to diabetes varied according to age, islet autoantibodies, and genetic markers of susceptibility.

RESEARCH DESIGN AND METHODS

Individuals with ICA > or = 20 JDF U were identified from 4,423 family members recruited to prospective family studies in the U.K. Subjects were followed for up to 18 years. Antibodies to insulin, GAD, and IA-2 were measured in the first sample, and HLA class II typing was performed.

RESULTS

Of 147 family members with ICA > or = 20 JDF U on at least one occasion, 29 developed type 1 diabetes after a median of 3.2 years (maximum 18.1). The cumulative risk of developing diabetes within 15 years was 47% (95% CI 28-67) for all family members with ICA > or = 20 JDF U, 2.8% (0-8.2) for those with ICA alone, and 66% (44-87) for those with at least one additional autoantibody marker. There were no differences in age, HLA class II type, or levels of ICA, insulin autoantibodies, or IA-2 antibodies between those who developed diabetes within 5 years of testing and those who developed diabetes after this time. GAD antibody levels we ..., however, higher in those who progressed more slowly.

CONCLUSIONS

Family members with ICA alone are at low risk of progression to diabetes. Rapid development of disease after ICA detection could not be distinguished from delayed development on the basis of autoantibodies or markers of genetic susceptibility, and those with multiple antibodies remained at high risk throughout long-term follow-up. This suggests that all family members with multiple islet autoantibodies are destined to develop autoimmune diabetes.

Insulin autoantibodies: more specific than proinsulin autoantibodies for prediction of type 1 diabetes

Proinsulin autoantibodies (PAA) are a potential alternative to insulin autoantibodies (IAA) for the prediction of type 1 diabetes. We measured the prevalence of PAA and IAA in 179 patients with newly diagnosed type 1 diabetes and 1028 schoolchildren, and compared the potential of these antibodies for disease prediction. Antibodies were measured using a novel microassay in which screening for binding of radio-labelled antigen was followed by competitive displacement. Thresholds for both antigen binding and competitive displacement were selected so that equivalent numbers of patients with type 1 diabetes were identified by the proinsulin and insulin antibody assays. Similar numbers of schoolchildren were found to have insulin and proinsulin binding above the screening threshold but, after competitive displacement, the prevalence of PAA (3.7%) was more than twice that of IAA (1.4%) with 66% sensitivity. Both PAA and IAA were present in 113 (63%) of patients, as against 0.8% of schoolchildren, implying that individuals with both antibodies are at particularly high risk of disease. The majority of samples with IAA or PAA were displaced with both insulin and proinsulin, suggesting that the main epitopes recognized by these antibodies are on the insulin molecule. We conclude that IAA are more specific than PAA for the prediction of type 1 diabetes.

Optimized autoantibody-based risk assessment in family members. Implications for future intervention trials

OBJECTIVE

To determine the best autoantibody-based testing strategy for recruiting relatives for future intervention trials and to establish the role of islet cell antibodies (ICAs) within this strategy.

RESEARCH DESIGN AND METHODS

ICAs, insulin autoantibodies (IAAs), GAD antibodies, and IA-2 antibodies were determined in serum samples at study entry of 3,655 non-diabetic first-degree relatives of patients with type 1 diabetes who were followed for a median of 5.5 years. The cumulative risk of diabetes associated with single and combined antibody marker levels of > or = 97.5th percentile in schoolchildren was calculated by using life-table analysis.

RESULTS

Of the 26 relatives who developed insulin-requiring diabetes during follow-up, 16 were aged < 20 years and 7 were aged 20-39 years at study entry. Of the 23 cases aged < 40 years, 83% had IA-2 and/or GAD antibodies, and 87% had IAA and/or GAD antibodies > or = 97.5th percentile compared with 61% who had ICAs of > or = 5 Juvenile Diabetes Foundation units (JDF U). A two-step strategy with parallel testing for IA-2/GAD antibodies followed by IAA testing identified 50% of cases aged < 20 years and was associated with a 71% risk within 10 years. In subjects aged 20-39 years, this strategy conferred a 51% risk, whereas using ICAs as the second test gave 86% sensitivity and a 74% risk. Primary screening for IA-2 and/or GAD antibodies followed by testing for IAA and/or ICA antibodies achieved the highest sensitivity in both age-groups and conferred a 63% risk. In contrast, ICAs of > or = 20 JDF U (the inclusion criteria for the European Nicotinamide Diabetes Intervention Trial) gave 48% sensitivity and 35% risk.

CONCLUSIONS

ICA testing can be replaced as a primary screening measure by IA-2/GAD or IAA/GAD antibody testing. The sensitivity of ICAs (used alone or in combination with IAAs) gives them a useful role in second-line testing. Combination testing could reduce the size of screening populations needed for recruitment in future intervention trials by approximately 50% compared with testing based on ICAs alone.

Evaluation of a high-throughput second antibody radiobinding assay for measuring IgA antibodies to human tissue transglutaminase

We describe a novel high-throughput radiobinding assay for IgA antibodies to tissue transglutaminase (TG) which uses second antibody precipitation to isolate immune complexes. Using this assay, 24 of 25 patients with untreated coeliac disease (96%) and nine of 526 healthy blood donors (2%) had TG antibody levels above a threshold defined by the 97.5th centile of 347 schoolchildren. All patients and five of the nine blood donors with transglutaminase antibodies above this threshold were endomysial antibody (EMA) positive. Using this threshold, 410/445 (92%) routine clinical samples were concordant for TG antibodies and EMA, including 72 of 75 with EMA. TG antibodies above the 97.5th centile were found in 32 of 370 EMA negative samples, 15 of whom had anti-gliadin antibodies (AGA), histologically proven coeliac disease or partial villous atrophy. We conclude that this assay achieves a sensitivity and a specificity at least equivalent to those of EMA. It is technically simple and suitable for coeliac disease screening.

Measurement of nicotinamide and N-methyl-2-pyridone-5-carboxamide in plasma by high performance liquid chromatography

We describe a simple and reproducible method for simultaneous determination of nicotinamide and its major human biological metabolite N-methyl-2-pyridone-5-carboxamide (2pyr). Previous assays for nicotinamide in plasma and in urine have been complicated by the use of tedious extraction procedures or HPLC conditions which, although often allowing simultaneous analysis of several metabolites, add to the difficulties of performing multiple analyses. The procedure we describe is simple, using a rapid column clean-up of samples prior to injection, which can then be done using an autosampler. Both nicotinamide and its major metabolite 2pyr can be assayed rapidly, with good reproducibility, and at the same time.

The British Diabetic Association Cohort Study, I: all-cause mortality in patients with insulin-treated diabetes mellitus

AIMS

To assess mortality in patients with diabetes incident under the age of 30 years.

METHODS

A cohort of 23 752 diabetic patients diagnosed under the age of 30 years from throughout the United Kingdom was identified during 1972-93 and followed up to February 1997. Following notification of deaths during this period, age- and sex-specific mortality rates, attributable risks and standardized mortality rates were calculated.

RESULTS

The 23 752 patients contributed a total of 317 522 person-years of follow-up, an average of 13.4 years per subject. During follow-up 949 deaths occurred in patients between the ages of 1 and 84 years, 566 in males and 383 in females. All-cause mortality rates in the patients with diabetes exceeded those in the general population at all ages and within the cohort were higher for males than females at all ages except between 5 and 15 years. The relative risk of death (standardized mortality ratio, SMR), was higher for females than males at all ages, being 4.0 (95% CI 3.6-4.4) for females and 2.7 (2.5-2.9) for males overall, but reaching a peak of 5.7 (4.7-7.0) in females aged 20-29, and of 4.0 (3.1-5.0) in males aged 40-49. Attributable risks, or the excess deaths in persons with diabetes compared with the general population, increased with age in both sexes.

CONCLUSIONS

This is the first study from the UK of young patients diagnosed with diabetes that is large enough to calculate detailed age-specific mortality rates. This study provides a baseline for further studies of mortality and change in mortality within the United Kingdom.

The British Diabetic Association Cohort Study, II: cause-specific mortality in patients with insulin-treated diabetes mellitus

AIMS

To measure cause-specific mortality, by age, in patients with insulin-treated diabetes incident at a young age.

METHODS

A cohort of 23 752 patients with insulin-treated diabetes diagnosed under the age of 30 years, from throughout the United Kingdom, was identified during 1972-93 and followed to February 1997. Death certificates have been obtained for deaths during the follow-up period and cause-specific mortality rates and standardized mortality ratios by age and sex are reported.

RESULTS

During the follow-up period 949 deaths occurred and at all ages mortality rates were considerably higher than in the general population. Acute metabolic complications of diabetes were the greatest single cause of excess death under the age of 30 years. Cardiovascular disease was responsible for the greatest proportion of the deaths from the age of 30 years onwards.

CONCLUSIONS

Deaths in patients with diabetes diagnosed under the age of 30 have been reported and comparisons drawn with mortality in the general population. To reduce these deaths attention must be paid both to the prevention of acute metabolic deaths and the early detection and treatment of cardiovascular disease and associated risk factors.

Capillary whole blood measurement of islet autoantibodies

OBJECTIVE

Islet cell antibody (ICA) measurements in serum are used for large-scale screening to identify subjects who are at high risk of developing type 1 diabetes. The aim of this study was to adapt measurements to capillary whole blood samples to facilitate and reduce screening costs.

RESEARCH DESIGN AND METHODS

GAD65, IA-2, and combined GAD65/IA-2 antibody tests were performed on patients with type 1 diabetes, first-degree relatives of patients, and control subjects, and results from serum, plasma, whole venous blood, and capillary whole blood lysates were compared. Measurements obtained in serum and eluates from dried capillary blood spots from 36 ICA+ first-degree relatives were also compared.

RESULTS

GAD65, IA-2, and combined GAD65/IA-2 antibody levels were completely concordant with measurements obtained from serum, plasma, whole venous blood, and capillary whole blood lysates. Antibody levels obtained in eluates from dried capillary blood spots were lower than corresponding serum samples, and weak antibodies were not detected.

CONCLUSIONS

Initial screening for diabetes risk can be performed using one drop of capillary whole blood without further processing to separate serum. This method should be considered as a way to simplify and reduce costs of screening programs.