IgA-tTG Levels Research Articles

TTG IgA in Functional Constipation: Is It Rational to Be Evaluated?

Background: It is suggested that constipation could be due to celiac disease (CD); therefore, this study aimed to determine the prevalence of positive tissue transglutaminase (tTG) IgA test among children with functional constipation (FC). Methods: In this case-control study, 182 consecutive patients with FC who fulfilled the Rome III criteria as cases were compared with 240 healthy children as the control group in terms of suspicious CD by measuring the serum tTG IgA level. Results: There was a significant difference in favor of the case group in terms of serum tTG IgA levels (P = 0.000). The probability of having CD would change based on belonging to each group (case/control odds ratio [OR] = 0.222). Conclusion: With respect to these data, tTG IgA level was observed to be significantly higher in patients relative to healthy children; therefore, it is recommended that patients be screened for CD through the tTG IgA.

A Retrospective Application of the European Society for Paediatric Gastroenterology Hepatology and Nutrition Guidelines for Diagnosis of Coeliac Disease in New Zealand Children

In 2012 the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) published an updated guideline for the diagnosis of Coeliac disease, allowing symptomatic individuals with appropriate serology and HLA genotype to be diagnosed without a small bowel biopsy. This retrospective study aimed to assess the applicability of this guideline to children in New Zealand. Children less than 16 years of age investigated for coeliac disease with small bowel biopsy in Christchurch Hospital between January 2010 and December 2012 were identified. The results of those with tissue transglutaminase IgA (tTG) levels greater than 50 units (10 times upper limit of normal), positive endomysial antibodies and HLA DQ2/DQ8 were used to calculate sensitivity and specificity. Data from 160 children was available: 70 had biopsy-confirmed Coeliac disease, and 90 had negative biopsies. Limited data precluded application of the guidelines to all patients. Using only tTG data, levels above 50 units provided a sensitivity of 67% and a specificity of 92%. Specificity increased to 97% when limited EMA and HLA DQ2/DQ8 data was added. Despite limited data, applying the ESPGHAN guidelines in the Christchurch paediatric population over this period produced a high specificity (97%). Prospective studies are now required to confirm these findings.

Screening of celiac disease in children with Henoch-Schoenlein purpura.

Prevalence of celiac disease (CD) is 2.42 % in healthy Turkish children. The frequency of IgA-associated disorders is increased in CD. Henoch-Schoenlein purpura (HSP) is an IgA-associated vasculitis. Association of HSP with CD has not been evaluated. We aimed to evaluate whether CD prevalence is increased in children with HSP. Children with HSP were evaluated for demographic, anthropometric, clinical, and laboratory data including urinalysis, complete blood count, albumin, creatinine, and IgA levels. In addition, tTG-IgA, EMA-IgA, anti-DGP-IgA, and IgG antibody levels were measured. Seropositive patients were evaluated by endoscopic small bowel biopsy. The rate of CD seropositivity and confirmed CD in HSP patients was compared to the rate in healthy Turkish children. There were 42 children (25 male) with HSP. No patient had classical CD symptoms, but two patients had growth failure. None of them had IgA deficiency, anemia or hypoalbuminemia. Celiac serology was positive in five (12 %) children. Endoscopic evaluation was performed in four patients, and two (5 %) of them were confirmed to have CD. Prevalence of both CD seropositivity and histologically confirmed CD in children with HSP was significantly higher compared to healthy Turkish children (p < 0.001 and p = 0.019, respectively). CD seropositivity rate in children with HSP (12 %) is significantly higher than the rate in healthy children. Although the number of children with HSP is small in this preliminary study, this result suggests that celiac screening may be considered in children with HSP.

Does celiac sero-diagnosis always require a tertiary referral centre confirmation? Our experience in Marche region

Background: Evaluation of celiac autoantibodies is a crucial step in the diagnostic algorithm of celiac disease (CD). The need of intestinal biopsy mainly relies on TTG IgA levels (with biopsy still needed if levels are less than 10 times the ULN, subdiagnostic levels [SDLs]). Aim: To evaluate the agreement of serological CD markers between different regional peripheral laboratories (PLs) and our referral regional laboratory (RL) in Salesi Children’s Hospital (Ancona). Methods: Childrenwith a final diagnosis of CD confirmed in our centre (May 2014–April 2015) and a previous (within 1 month) serological evaluation (TTG IgA and DGP IgG) performed in one PLs were included. Levels (times the ULN) of TTG IgA and DGP IgGwere compared between the RL and the PLs. Results: Forty-one subjects (mean age: 6.2 years) with a diagnosis of CD were included. Overall the RL confirmed abnormal CD antibodies detected in PLs in 100% of patients. A small proportion were discordant in TTG IgA levels: 10% with SDLs detected in a PL had diagnostic levels in the RL, while 17% with>10 times the ULN in a PLwere found to have SDLs in the RL, requiring confirmation by biopsy. Bland Altaman analysis suggested that the levels of TTG IgA in the RL was on average 4.8 times higher (SD 14.8) than the levels in the PLs with wide limits of agreement (95% limit of agreement: −33.83 to 24.20 times). Conclusion: In our regional setting the determination of serological CDmarkers in a PLswas overall reliable andwe found a good correlationwithmeasurement in the RL. Howeverwe still consider the confirmation in our RL a fundamental step in the diagnostic process.

Celiac disease can be predicted by high levels of anti-tissue transglutaminase antibodies in population-based screening.

The aim of the present study was to evaluate any potential correlation between anti-tissue transglutaminase antibodies of type immunoglobulin A (tTG-IgA) and the degree of gluten-induced enteropathy in children participating in a screening study for celiac disease (CD) and to assess to what extent the revised European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) guidelines cover this group of patients. The present study is a substudy of a cross-sectional CD screening study, Exploring the Iceberg of Celiacs in Sweden, a 2-phased study performed during 2005 to 2006 and 2009 to 2010. The 13,279 participating children had a blood test obtained, and those with positive tTG-IgA were recommended a small intestinal biopsy. The tTG-IgA levels at the time of biopsy were compared with those at the assessment of the biopsy. There were 267 children included, of whom 230 were diagnosed as having CD. Of all of the children, 67 children had low tTG-IgA levels (<5 U/mL), of whom 55% had Marsh 3 lesions. All of the children with tTG-IgA levels exceeding 10 times the upper limit of normal values of 5 U/mL, that is, 50 U/mL, were diagnosed as having CD. Lowering the cutoff to 3 U/mL, all but 1 child with 30 U/mL got CD diagnosis. By adopting the revised ESPGHAN criteria, biopsies could have been omitted in one-fourth of all of the patients. Our results indicate that the criteria may be useful even in screened children. Further studies are needed to confirm whether the 2012 ESPGHAN guidelines should be revised to also apply to the populations being screened.

Serologic evaluation of celiac disease in patients with beta thalassemia major and control.

This study reports evaluated prevalence of CD in patients with Beta-thalassemia major. Celiac Disease (CD) is an autoimmune disorder triggered by ingestion of gluten in genetically predisposed individuals. In this case-control study in a period of 3 years, which was performed on 620 children in two groups of Beta-thalassemia major patients (n=200) and control (n=420), serum tissue transglutamianse (tTG) IgA levels were measured. The two groups were compared together in terms of tTG IgA levels, and p<0.05 was considered significant. The means of serum tTG IgA levels in patients with Beta-thalassemia major and control groups were 28.81±68.44 and 6.94±6.68 U/mL, respectively. There was a significant difference in favor of the case group (p=0.000). Body mass index in the two case and control groups had a significant difference (t=3.859, p=0.001). Belonging to each group will change the probability of having less than 20 in tTG IgA (odds=0.285) and it means that belonging to the control group has a protective role. There is only a significant association in the case of all population (r=0.102, p=0.011). Body mass index in the two case and control groups had a significant difference (t=3.859, p=0.001). Probability of CD should be considered since the prevalence of CD is high in patients with and Beta-thalassemia major. Patients with thalassemia major are recommended for screening for CD.

BIOPSY IN COELIAC DISEASE DIAGNOSIS: WHEN IS IT NECESSARY?

Duodenal biopsy is considered the Gold Standard for Coeliac Disease (CD) diagnosis at the moment. As the ESPGHAN guidelines published in 2012 state, CD can be diagnosed without biopsy in patients with typical symptoms and tTG-IgA levels which are ten times over the reference values. The aim of this study is to establish the association between tTG-IgA levels and anatomic lesions, by redefining the biopsy role in the CD diagnosis. The research focuses on Positive Predictive Value of serological tests, also in patients without typical clinical presentation. In this retrospective study, clinical and laboratory data have been analysed in 95 pediatric patients, assessed at the Pediatric Unit in Siena from 2005 to 2011. Eightysix patients have been included, with typical symptoms, monosymptomatic or asymptomatic, all with tTG-IgA &gt;9U/ml and a biopsy report. Patients have been divided into 5 groups (A-E) according to their tTG-IgA levels: A, &gt;100 UI/ml; B, 80- 99 UI/ml; C, 60-79 UI/ml; D, 40-69 UI/ml; E, 9-39 UI/ml. A Positive Predictive Value (PPV) for each group has been evaluated. 78,9 of the patients included reported a positive biopsy. Biopsy was positive in 100 of the patients in groups A, B, C, with a Positive Predictive Value of 100%. PPV was 75% in group D and 78,7% in group E. In group A patients were divided in 3 subgroups: typical symptoms (67.4%), monosymptomatic (16.2%) and asymptomatic (16.2%). All of them (100%) had a positive biopsy report. PPV was 100% in typical symptoms subgroup as well as in monosymptomatic and asymptomatic patients. This study confirms the ESPGHAN Recommendation, concluding that in patients with typical symptoms and tTg-IgA ten times over the reference values the biopsy could be avoided. These results open the question whether the biopsy can be also avoided in patients with tTG-IgA ten times over the reference values even if monosymptomatic or asymptomatic. This approach could be followed by 50% of biopsies avoided in our case series.

Serum I‐FABP as marker for enterocyte damage in coeliac disease and its relation to villous atrophy and circulating autoantibodies

Enterocyte damage is the hallmark of coeliac disease (CD) resulting in malabsorption. Little is known about the recovery of enterocyte damage and its clinical consequences. Serum intestinal fatty acid binding protein (I-FABP) is a sensitive marker to study enterocyte damage. To evaluate the severity of enterocyte damage in adult-onset CD and its course upon a gluten-free diet (GFD). Furthermore, the correlation among enterocyte damage, CD autoantibodies and histological abnormalities during the course of disease is studied. Serum I-FABP levels were determined in 96 biopsy-proven adult CD patients and in 69 patients repeatedly upon a GFD. A total of 141 individuals with normal antitissue transglutaminase antibody (IgA-tTG) levels served as controls. I-FABP levels were related to the degree of villous atrophy (Marsh grade) and IgA-tTG. I-FABP levels were elevated in untreated CD (median 691 pg/mL) compared with controls (median 178 pg/mL, P < 0.001) and correlated with Marsh grade (r = 0.265, P < 0.05) and IgA-tTG (r = 0.403, P < 0.01). Upon a GFD serum levels decreased significantly, however, not within the range observed in controls, despite the common observed normalisation of IgA-tTG levels and Marsh grade. CD patients with elevated I-FABP levels nonresponding to GFD showed persistent histological abnormalities. Enterocyte damage assessed by serum I-FABP correlates with the severity of villous atrophy in coeliac disease at the time of diagnosis. Although enterocyte damage improves upon treatment, substantial enterocyte damage persists despite absence of villous atrophy and low IgA-tTG levels in the majority of cases. Elevated I-FABP levels nonresponding to gluten-free diet are indicative of histological abnormalities and warrant further evaluation.

A monocenter retrospective study of serological,histological and genetic characteristics of celiac disease in Northern Central Italy

Objective: To examine the seroprevalence, correlates and characteristics of Celiac disease (CD) in a population sample of a Northern Central Area of Italy, by a monocenter retrospective study. Methods: Between 2006 and 2010, serum samples of 9371 subjects (age range 6 months to 91 years) were screened for tissue transglutaminase IgA antibodies (IgA-tTG) by the Immunologia-Allergologia Unit of AUSL1 Massa-Carrara, an area with a population of approximately 150,000. Endomysial IgA antibodies (EMA), HLA typing and small-bowel biopsy were also performed when indicated. Results: Of the 9371 subjects, 269 (2.87%) had positive antibody tests. The population was divided into several age groups and the highest prevalence (5.63%) was found in the 6 months-3 years group. The prevalence of IgA-tTG positivity was double in females compared to males. All IgA-tTG positive patients that were genotyped carried HLA-DQ2 or DQ8, none was a5 positive only. In positive IgA-tTG sera, levels of IgA-tTG were significantly higher in EMA positive than in EMA negative sera (p in children and in adults. Ninety-five/269 IgA-tTG positive subjects underwent biopsy. IgA-tTG levels were different according to the histological degree of the lesion. When EMA were evaluated in IgA-tTG positive subjects the number of EMA negative sera was significantly higher in adults than in children. Conclusions: In summary, this study provides a monocenter retrospective analysis of serological, histological and genetic parameters of subjects with suspicion of CD in an area of Northern Central Italy from 2006 to 2010.

BIOPSY IN COELIAC DISEASE DIAGNOSIS: WHEN IS IT NECESSARY?

Duodenal biopsy is considered the Gold Standard for Coeliac Disease (CD) diagnosis at the moment. As the ESPGHAN guidelines published in 2012 state, CD can be diagnosed without biopsy in patients with typical symptoms and tTG-IgA levels which are ten times over the reference values. The aim of this study is to establish the association between tTG-IgA levels and anatomic lesions, by redefining the biopsy role in the CD diagnosis. The research focuses on Positive Predictive Value of serological tests, also in patients without typical clinical presentation. In this retrospective study, clinical and laboratory data have been analysed in 95 pediatric patients, assessed at the Pediatric Unit in Siena from 2005 to 2011. Eightysix patients have been included, with typical symptoms, monosymptomatic or asymptomatic, all with tTG-IgA &gt;9U/ml and a biopsy report. Patients have been divided into 5 groups (A-E) according to their tTG-IgA levels: A, &gt;100 UI/ml; B, 80- 99 UI/ml; C, 60-79 UI/ml; D, 40-69 UI/ml; E, 9-39 UI/ml. A Positive Predictive Value (PPV) for each group has been evaluated. 78,9 of the patients included reported a positive biopsy. Biopsy was positive in 100 of the patients in groups A, B, C, with a Positive Predictive Value of 100%. PPV was 75% in group D and 78,7% in group E. In group A patients were divided in 3 subgroups: typical symptoms (67.4%), monosymptomatic (16.2%) and asymptomatic (16.2%). All of them (100%) had a positive biopsy report. PPV was 100% in typical symptoms subgroup as well as in monosymptomatic and asymptomatic patients. This study confirms the ESPGHAN Recommendation, concluding that in patients with typical symptoms and tTg-IgA ten times over the reference values the biopsy could be avoided. These results open the question whether the biopsy can be also avoided in patients with tTG-IgA ten times over the reference values even if monosymptomatic or asymptomatic. This approach could be followed by 50% of biopsies avoided in our case series.

BIOPSY IN COELIAC DISEASE DIAGNOSIS: WHEN IS IT NECESSARY?

Duodenal biopsy is considered the Gold Standard for Coeliac Disease (CD) diagnosis at the moment. As the ESPGHAN guidelines published in 2012 state, CD can be diagnosed without biopsy in patients with typical symptoms and tTG-IgA levels which are ten times over the reference values. The aim of this study is to establish the association between tTG-IgA levels and anatomic lesions, by redefining the biopsy role in the CD diagnosis. The research focuses on Positive Predictive Value of serological tests, also in patients without typical clinical presentation. In this retrospective study, clinical and laboratory data have been analysed in 95 pediatric patients, assessed at the Pediatric Unit in Siena from 2005 to 2011. Eightysix patients have been included, with typical symptoms, monosymptomatic or asymptomatic, all with tTG-IgA >9U/ml and a biopsy report. Patients have been divided into 5 groups (A-E) according to their tTG-IgA levels: A, >100 UI/ml; B, 80- 99 UI/ml; C, 60-79 UI/ml; D, 40-69 UI/ml; E, 9-39 UI/ml. A Positive Predictive Value (PPV) for each group has been evaluated. 78,9 of the patients included reported a positive biopsy. Biopsy was positive in 100 of the patients in groups A, B, C, with a Positive Predictive Value of 100%. PPV was 75% in group D and 78,7% in group E. In group A patients were divided in 3 subgroups: typical symptoms (67.4%), monosymptomatic (16.2%) and asymptomatic (16.2%). All of them (100%) had a positive biopsy report. PPV was 100% in typical symptoms subgroup as well as in monosymptomatic and asymptomatic patients. This study confirms the ESPGHAN Recommendation, concluding that in patients with typical symptoms and tTg-IgA ten times over the reference values the biopsy could be avoided. These results open the question whether the biopsy can be also avoided in patients with tTG-IgA ten times over the reference values even if monosymptomatic or asymptomatic. This approach could be followed by 50% of biopsies avoided in our case series.

Reduction of tissue transglutaminase autoantibody levels by gluten-free diet is associated with changes in subsets of peripheral blood lymphocytes in children with newly diagnosed coeliac disease

Tissue transglutaminase (tTG) autoantibodies decline after gluten-free diet in patients with coeliac disease. We tested the hypothesis that gluten-free diet-induced change in tTG autoantibody levels affects subsets of peripheral blood lymphocytes. Peripheral blood was obtained from 20 children with biopsy-proven active coeliac disease. Gluten-free diet was initiated and the children examined again after three and six months. tTG autoantibodies were measured in radioligand binding assays and lymphocyte subsets by flow cytometry. IgA-tTG levels at diagnosis, 2204 U/ml (median, range 113-24990), were reduced over six months to 76 U/ml (median, range 1-1261) (P < 0.001). At six months, 12/20 (60%) children had reduced their IgA-tTG levels to < 100 U/ml and these children showed a decrease in B cells (mean change -3.8%, P = 0.014), CD4+ T cells (mean -4.32%, P = 0.011) and CD4+ T cells expressing CD25high (mean change -0.62%, P = 0.036). In contrast, the CD4+CD25(high)CCR4+ T cell population increased during the same period (mean change 11.5%, P = 0.0036). The decline in IgA-tTG levels correlated to the decrease in B cells (r = 0.56, P = 0.01), CD4+ T cells (r = 0.66, P = 0.004) as well as CD4+CD25high T cells (r = 0.59, P = 0.01). A negative correlation was found between the decline in IgA-tTG and CD4+CD25high T cells expressing CD45RO (r = -0.49, P = 0.03) and CCR4 (r = -0.54, P = 0.01). This is the first observational study on the effect of gluten-free diet on concurrent changes of tTG autoantibodies and specific peripheral blood lymphocyte subsets. Our data suggest that flow cytometry may be a useful complement to tTG autoantibodies when studying the effects of gluten-free diet in children with coeliac disease.

LACK OF CORRELATION OF COPY NUMBER OF HLA DQA1A*05 DQB1*02 AND TISSUE TRANSGLUTAMINASE LEVELS IN UNTREATED CELIAC DISEASE

Background: Celiac Disease is an autoimmune disorder of the small intestine characterized by intolerance to gluten. More than 90% of the patients with celiac disease have the human leukocyte antigen DQA1*05 DQB1*02. A gene dosage effect has been proposed for this high-risk genotype. In CD, there is an autoimmune response to the enzyme tissue transglutaminase, causing the production of immunoglobulin A autoantibodies, which are quantitative and resolve with improvement of intestinal inflammation after adherence to a gluten-free diet. Methods: Blood samples were collected from relatives of patients with known celiac disease as part of a family study to identify genes for celiac disease. These patients were screened for immunogloglobulin A endomysial antibodies. Positive sera were then evaluated for quantitative levels of immunoglobulin A tissue transglutaminase antibodies and HLA genotyping was performed. Results: One hundred sixteen family members were found to be positive for immunoglobulin A endomysial antibodies. Tissue transglutaminase levels for this group had a mean of 111 (±SD 93) with a range of 4-258. There was no correlation between IgA tTG levels and age or sex of the patients. Twelve patients had no copies of DQA1*05DQB1*02,82 had 1 copy, and 22 had 2 copies. The means for IgA tTG Ab levels for the 3 groups were (1) zero copies, mean = 129 Units (2) one copy, mean = 111 units (3) two copies, mean = 100 units. There were no statistical differences between the IgA tTG Ab levels in the 3 groups or when or when the presence of the DQB1*02 genotype alone was evaluated. Conclusion: HLA genotype, although it is strongly correlated with CD and does not correlate with the level of IgA tTG Ab.

SEROLOGICAL ANALYSES OF UNAFFECTED PRESUMED GENE CARRIERS OF CELIAC DISEASE

Celiac disease (CD) is known to be familial but its inheritance pattern is not fully understood. Serologic tests are used to identify at risk individuals in CD families. We defined presumed gene carriers for celiac disease as individuals testing negative for IgA endomysial antibody, who have both a CD affected parent, sibling or cousin and a CD affected child. We hypothesized that presumed CD gene carriers would have unique serological profiles. Methods: We measured and compared IgG and IgA tissue transglutaminase (tTG), endomysial antibody (EMA) antigliadin antibody (GA) and total serum IgA in presumed gene carriers, HLA DQ2+ organ donors, and Red Cross blood donors. Results: There were no significant differences in EMA, GA, or IgA tTG levels in controls and presumed carriers. Presumed gene carriers had significantly elevated total serum IgA levels compared to DQ2 and blood donor controls (Table 1). The levels of IgG tTG were also significantly above those of the controls (Table 2).TABLE 1: Serum IgA Levels (mg/dL)TABLE 2: IgG tTG levelsConclusion: Higher total serum IgA levels in CD family members who are presumed gene carriers could be an indication of an accelerated mucosal immune response. The increased IgG tTG levels, indicates a slight tendency towards an immune response to transglutaminase antigen. However, the data clearly indicate that no test is clinically useful in differentiating presumed gene carriers from controls and there does not appear to be a unique serologic pattern differentiating the presumed gene carrier family member.

DO PATIENTS WITH AUTOIMMUNE THYROID DISEASE ALSO HAVE CELIAC DISEASE?

A limited number of studies suggest an increased incidience of celiac disease (CD) in individuals with autoimmune thyroid disease. We sought to determine the prevalence of tTG-IgA antibodies associated with CD and the prevalence of CD in patients with autoimmune thyroid disease in the United States. Our results will also be compared with the results obtained in Europe. Methods: 50 pediatric patients with autoimmune thyroid disease participated in this study. After written informed consent was obtained, blood was drawn to determine their tissue transglutaminase IgA (tTG-IgA) levels and total IgA levels. If the tTG-IgA levels were positive, an endoscopy and biopsy were performed to confirm the diagnosis of CD. Results: Four of our patients (8%) had positive tTG-IgA. Of those, 3 underwent endoscopy. One (2%) of our patients was diagnosed with CD based on the histopathology using the Marsh Criteria. Two patients' biopsies were negative, and one patient refused endoscopy. Our results showed a lower correlation between autoimmune thyroid disease and CD than do the results from the European literature which showed a range from 14-40%. However, we did find a higher correlation (2%) of positive tTG-IgA in those patients with autoimmune thyroid disease than in the normal population in the US which is 0.4-0.9%. Discussion: European literature suggests that approximately 14-40% of their patients with autoimmune thyroid disease have CD. Eight percent of our patients had positive tTG-IgA which was significantly higher compared to normal populations. However, only 2% of our autoimmune thyroid patients also have CD. tTG-IgA positivity by itself should not be interpreted as diagnostic of CD. However, because there is a higher chance of having CD with autoimmune thyroid disease than those who do not, we also recommend measuring tTG-IgA levels in patients with autoimmune thyroid disease. This must be followed by histopathological examination for CD when tTG-IgA is positive.

Calcium activation of tissue transglutaminase in radioligand binding and enzyme-linked autoantibody immunoassays in childhood celiac disease

Conflicting data have been published concerning the effect of calcium on binding of autoantibodies to tissue transglutaminase (tTG) in celiac disease (CD). IgA-tTG and IgG-tTG were measured with radioligand binding assays (RBA) using human recombinant (hr) (35)S-tTG produced in lysate of rabbit reticulocytes and with guinea pig (gp) tTG ELISA in 51 CD children (median: 5.7 years) and 35 controls (median: 2.2 years). Assays were performed with and without calcium. In hr-tTG RBA, IgA-tTG levels remained unchanged after calcium detecting 50/51 CD children and 1/35 controls (p<0.0001). IgG-tTG levels decreased with calcium (p<0.0001) in CD children and detected 48/51 with and 49/51 without calcium as compared to 1/35 controls (p<0.0001). In gp-tTG ELISA, levels increased with calcium (p<0.0001) making it possible to detect an additional three to a total of 50/51 with IgA-tTG and 13 to 39/51 CD children with IgG-tTG compared to 4/35 and 8/35 controls (respectively, p<0.0001). Rabbit reticulocytes displayed calcium-dependent tTG activity. Calcium increased binding of IgA-tTG and IgG-tTG in the ELISA test. The reverse effect observed in RBA may be explained by competitive binding between calcium activated native rabbit reticulocyte tTG and hr (35)S-tTG. tTG autoantibody assays may need taking calcium into account for accurate diagnostic sensitivity and specificity for CD.

Using radioligand-binding assays to measure tissue transglutaminase autoantibodies in young children

To measure autoantibodies against tissue transglutaminase (tTG) in young children prospectively screened for coeliac disease (CD). In total, 652 children aged 2.9 (2.5-4.2) y were analysed for IgA-tTG and IgG-tTG with radioligand-binding assays and IgA endomysial antibodies (EMA) by indirect immunofluorescence. Antibody-positive children were retested after 1.2 (range 0.2-1.9) y. Intestinal biopsy was performed on children with persistently high antibody levels. In total, 3.2% (95% CI: 1.9-4.6%) of the 652 children were positive for at least one antibody at baseline: 2.5% (95% CI: 1.3-3.7%) for IgA-tTG, 1.7% (95% CI: 0.7-2.7%) for IgG-tTG and 2.9% (95% CI: 1.6-4.2%) for IgA-EMA, respectively. Ten children were positive for all three antibodies, five for both IgA-tTG and EMA, four for EMA only, one for IgA-tTG and another for IgG-tTG. IgA-EMA titres correlated with IgA-tTG levels (r = 0.73, p = 0.0003). At follow-up, seven of 20 children remained positive for all three antibodies, three for IgA-tTG only, one for both IgA-tTG and EMA, one for IgA-tTG and IgG-tTG, and the remaining child refused further participation. Three biopsies showed villous atrophy, two increased intraepithelial lymphocytes and two normal findings. Biopsy was not performed in four children with low or declining tTG antibody levels at follow-up and in one child who declined. CD was evident in 0.5% (95% CI: 0.0-1.0%) (3/652). This study revealed a high number of young children positive for tTG antibodies as well as EMA, but the majority showed declining levels in both antibodies over time. We suggest using radioligand-binding assays for quantitative measurement of tTG antibodies when change in antibody levels is studied in young children.

Prediction of silent celiac disease at diagnosis of childhood type 1 diabetes by tissue transglutaminase autoantibodies and HLA.

The aims were to estimate the diagnostic sensitivity and specificity of autoantibodies to tissue transglutaminase (IgA- and IgG-tTG), gliadin (AGA) and endomysium (EMA) in relation to human leukocyte antigen (HLA)-DQB1 alleles to identify silent celiac disease at diagnosis of type 1 diabetes. IgA- and IgG-tTG were measured in radioligand binding assays in 165 type 1 diabetic patients. Data on HLA-DQB1 were available for 148 patients and on both AGA and EMA for 164 patients. For patients considered positive for AGA or EMA, or both, an intestinal biopsy was suggested. HLA-DQB1 typing was carried out by polymerase chain reaction and hybridization with allele specific probes. Three patients, left out from further study of antibodies, but not from HLA-DQB1 analysis, had treated celiac disease at diagnosis. Out of the other 162 type 1 diabetic patients tested, nine had IgA-tTG, six IgG-tTG, eight EMA, and 11 AGA. Biopsy was suggested for nine patients, of whom six showed villous atrophy, one did not and two refused to participate. Thus, silent celiac disease was probable in 8/162 and biopsy-verified in 6/162, where five patients were AGA-positive and six either EMA-, IgA-tTG- or IgG-tTG-positive. Of the 11 patients with celiac disease (three with treated and eight with silent celiac disease), 10 were HLA-DQB1-typed, of whom 65% (13/20) had the DQB1*02 allele, compared with 36% (100/276; p = 0.011) of those without celiac disease. IgA-tTG levels were higher in patients having either *02 or *0302 (0.6; -1.3-112.4 RU) compared with those not having these alleles (0.4; -0.7-3.4 RU; p = 0.023). IgA-tTG are HLA-DQB1*02-associated autoantibodies with high sensitivity and specificity for silent celiac disease at diagnosis of type 1 diabetes.