Antibody reactivity against human and guinea pig tissue transglutaminase in children with celiac disease

Overview of biomarkers for diagnosis and monitoring of celiac disease

Among the adverse reactions caused by wheat, celiac disease (CD) is the longest studied and best-known pathology. The more recently defined non-celiac gluten sensitivity (NCGS) presents with symptoms which are often indistinguishable from CD. Diagnosis of CD is based on serologic, molecular, and bioptic testing. The IgA anti-transglutaminase (tTG) test is considered highly important, as it shows high sensitivity and specificity and its levels correlate to the degree of intestinal damage. Small bowel biopsy can be avoided in symptomatic patients with IgA anti-tTG levels above 10× the manufacturer's cut-off. Recently, tests of anti-deamidated peptides of gliadin (DGP) have replaced classic anti-native gliadin (AGA) tests. DGP assays have a considerably higher diagnostic accuracy than AGA assays, especially in the IgG class, and can replace anti-tTG tests in patients with selective IgA deficiency. The combination of IgG anti-DGP plus IgA anti-tTG assays show greater sensitivity than a single test, with very high specificity. EMA tests have great diagnostic accuracy but are not recommended by all the latest guidelines because they are observer dependent. Biopsy must still be considered the gold standard for CD diagnosis. HLA-DQ genotyping can be used to screen asymptomatic children and in cases of histology/serology disagreement. About half of NCGS patients are DQ2 positive and have IgG AGA. To diagnose NCGS, first CD and wheat allergy must be excluded; then the wheat dependence of symptoms must be verified by a gluten-free diet and subsequent gluten challenge.

Accuracy of diagnostic antibody tests for coeliac disease in children: summary of an evidence report

OBJECTIVE

The aim of this study was to summarise the evidence from 2004 to September 2009 on the performance of laboratory-based serological and point of care (POC) tests for diagnosing coeliac disease (CD) in children using histology as reference standard.

PATIENTS AND METHODS

We searched MEDLINE and EMBASE for studies reporting on children for tests based on IgA and IgG anti-gliadin (AGA), endomysial (EmA), anti-transglutaminase-2 (TG2), and anti-deamidated gliadin peptides (DGP) antibodies or POC tests. For inclusion, histological analysis of duodenal biopsies and sensitivity and specificity for index tests had to be reported. Data were pooled and summary measures calculated for sensitivity, specificity, positive and negative likelihood ratios ("LR+", "LR-"), and diagnostic odds ratios (DOR). In case of elevated statistical heterogeneity, studies reaching 90% sensitivity or specificity were reported.

RESULTS

A total of 2510 articles were reviewed; 16 entered meta-analysis, reporting on 3110 patients (1876 with CD, 1234 without CD). For IgA-EmA, sensitivity was ≥90% in 7/11 studies and pooled specificity 98.2%. For IgA-anti-TG2, 11/15 studies yielded sensitivities ≥90% and 13/15 specificities ≥90%. For IgA-DGP, sensitivity ranged between 80.7% and 95.1% (specificity 86.3%-93.1%); for IgG-DGP between 80.1% and 98.6% (specificity 86.0-96.9%). IgA-EmA had the highest pooled DOR (554) and LR+ (31.8) for a laboratory test, followed by IgA-anti-TG2, IgG-DGP, IgA-DGP and IgA-AGA. POC tests showed a pooled sensitivity of 96.4% for IgA-TG2 (specificity 97.7%).

CONCLUSIONS

IgA-EmA and IgA-anti-TG2 tests appear highly accurate to diagnose CD. IgG-anti-DGP tests may help in excluding CD. IgA-AGA and IgA-DGP tests show inferior accuracy. POC tests may achieve high accuracy in the hands of experienced readers, but IgA-anti-TG2/EmA were superior.

Questionnaire-based case finding of celiac disease in a population of 8- to 9-year-old children

OBJECTIVE

Antibody screenings and diagnosis of celiac disease (CD) among children with type 1 diabetes have suggested that a considerable proportion of children with CD may, in fact, have preclinical (undiagnosed) symptoms. We aimed to test if a questionnaire would lead to significant case finding in an unselected population of 8- to 9-year-old children.

PATIENTS AND METHODS

The study population included 9880 children aged 8 to 9 years. Before the study, 13 children from the study population were known to have CD. We developed a questionnaire on the basis of 5 simple items suggestive of CD and mailed the questionnaire to the families of all children in the study population who resided in the County of Funen, Denmark. In total, 7029 respondents returned the questionnaire (70%); among them, 2835 children had 1 or more symptoms. These children were invited for a blood test to determine their human serum immunoglobulin A (IgA) anti-tissue transglutaminase antibody (anti-tTG) levels.

RESULTS

Of the 1720 children who were tested for the human serum IgA anti-tTG, 24 participants had a positive result (range: 20 to >150 U). Seventeen of these children underwent an upper endoscopy procedure. Fourteen children had histologic signs of CD (Marsh classification stage III). Fourteen children met the diagnostic criteria for CD. The prevalence proportion of patients who were newly diagnosed with CD was 0.14% (95% CI: 0.08-0.24) (14 of 9967), and the estimate of the minimum total prevalence proportion of children with CD was 0.27% (95% CI: 0.18-0.39) (27 of 9980). The maximal prevalence proportion of patients with newly diagnosed CD was 1.22% (95% CI: 0.76-1.90) (21 of 1720), including those participants who had a positive anti-tTG result but not a final diagnosis of CD. The ratio of known to minimally symptomatic CD was approximately 1:1.

CONCLUSION

A number of preclinical and low-grade symptomatic patients with CD may be identified by their responses to a mailed questionnaire.

Coeliac disease-specific tissue transglutaminase autoantibodies are associated with osteoporosis and related fractures in middle-aged women

OBJECTIVE

To investigate whether the serological marker for coeliac disease, tissue transglutaminase autoantibody (tTGAb), is associated with decreased bone mass density (BMD) and increased frequency of fractures in middle-aged women screened for osteoporosis.

MATERIAL AND METHODS

The study comprised 6480 women (mean age 56 years, range 50-64) who answered a number of questionnaires and who underwent dual X-ray absorptiometry of the wrist bone. Serum samples were analysed for tTGAb using radioligand binding assays. A tTGAb level of >4 U/ml was used to determine a positive value and a level of >17 U/ml was used as an alternative discrimination of high levels.

RESULTS

A tTGAb level >4 U/ml was found among 90/6480 (1.4%) women and correlated with lower BMD (multiple linear regression coefficient -382.1; 95% CI = - 673.6-90.7, p=0.011) and with fracture frequency (r=0.18, p=0.023). The 59 women with tTGAb levels >or=17 U/ml had a lower BMD (0.41+/-0.08 g/cm(2) versus 0.44+/-0.08 g/cm(2), p=0.001) and a lower T-score (-1.40+/-1.28 versus -0.90+/-1.40, p=0.003) as well as a higher prevalence of osteoporosis (13.4% versus 6.5%, p=0.008) compared with the remaining 6421 women with tTGAb levels <17 U/ml. Furthermore, fracture frequency was more pronounced in women with tTGAb levels >or=17 U/ml, among whom 19/59 (32.2%) had fractures during the study period compared with 1204/6421 (18.8%) among women with tTGAb levels <17 U/ml (p=0.009).

CONCLUSIONS

High levels of tTGAb indicating coeliac disease are associated with lower BMD and higher fracture frequency in women between 50 and 64 years of age. Osteometry is therefore warranted in middle-aged women detected with tTGAb.

Comparison of a novel whole blood transglutaminase-based ELISA with a whole blood rapid antibody test and established conventional serological celiac disease assays

OBJECTIVES

Serum immunoglobulin A-class tissue transglutaminase (tTG-ab) and endomysial antibody (EMA) tests play a key role in the diagnostic evaluation of celiac disease. Recently, a novel whole blood rapid test based on self-tissue transglutaminase (tTG) was developed for celiac disease case finding. Based on the same principle, a whole blood self-tTG enzyme-linked immunosorbent assay (ELISA), especially applicable to large-scale screening of celiac disease, has been produced. We assessed the value of this new test in celiac disease antibody detection.

PATIENTS AND METHODS

The new test uses endogenous tTG found in red blood cells of whole blood in IgA-class tTG-ab measurement by detecting tTG-tTG-ab complexes formed after hemolysis of the whole blood sample. Stored whole blood samples from 150 untreated celiac disease patients and 107 control individuals without celiac disease were evaluated, and the test results were compared with those of the whole blood rapid test, 2 conventional serum-based tTG-ab ELISA tests, and 2 EMA tests.

RESULTS

A total of 15 whole blood samples were found to be clotted or dried after storage and were excluded from further evaluation. The whole blood ELISA test had a specificity (98%) comparable to that of the conventional serological tests, the sensitivity (91%) being slightly lower. The test was concordant with the whole blood rapid test in 92% of cases, with 2 serological ELISA tests in 91% and 94% of cases and with EMA tests in 94% and 93% of cases.

CONCLUSIONS

Whole blood self-tTG-based testing is accurate in celiac antibody detection, also when an ELISA method is applied. The testing requires no serum separation or external tTG.

Antibodies against synthetic deamidated gliadin peptides and tissue transglutaminase for the identification of childhood celiac disease

BACKGROUND & AIMS

Children with celiac disease have antibodies against gliadin, tissue transglutaminase (tTG), or both antigens. The aim was to evaluate immunoglobulin (Ig)A and IgG antibodies to synthetic deamidated gliadin peptides (DGP) and human tTG as screening markers for childhood celiac disease.

METHODS

Antibodies were detected in enzyme-linked immunosorbent assay using anti-human IgA, IgG, or a combined conjugate of IgA and IgG (IgAG) against DGP, tTG, or both (DGP/tTG), in sera from 119 children with celiac disease, 57 disease controls, and 398 blood donors. Treatment with a gluten-free diet was evaluated in 20 children with celiac disease who were followed up for 6 months from diagnosis.

RESULTS

The highest sensitivity was accounted for IgAG-DGP/tTG at 100% (119 of 119), followed by IgA-tTG at 97% (115 of 119), IgG-DGP at 95% (113 of 119), IgA-DGP at 91% (108 of 119), and IgG-tTG at 13% (15 of 119). With respect to disease controls and blood donors, specificity was for IgAG-DGP/tTG at 89% (51 of 57) and at 97% (385 of 398), IgA-tTG at 96% (55 of 57) and at 98% (392 of 398), IgG-DGP at 86% (49 of 57) and at 99% (395 of 398), IgA-DGP at 91% (52 of 57) and at 92% (366 of 398), and IgG-tTG at 100%, respectively. The concordances between antibody assays were 87%-98%, except for comparisons with IgG-tTG (39%-41%). After 6 months of a gluten-free diet, the mean antibody levels decreased for all test results (P < .001).

CONCLUSIONS

The combined IgAG-DGP/tTG assay is recommended as a front-line screening test for the identification of childhood celiac disease and also could be used as a marker of dietary compliance.

Screening of the adult population in Iran for coeliac disease: comparison of the tissue-transglutaminase antibody and anti-endomysial antibody tests

BACKGROUND AND AIMS

Population-based studies for the prevalence of coeliac disease (CD) in west-Asian countries are scarce. We aimed to determine the prevalence of gluten-sensitive enteropathy (GSE) in the general population of northern and southern Iran, and evaluate the sensitivity and specificity of the anti-endomysial antibody (EMA) immunofluorescent test and the enzyme-linked immunosorbent assay-based test for determination of the IgA anti-tissue transglutaminase antibody (tTG-Ab) using the human recombinant transglutaminase antigen for the detection of CD in screening the asymptomatic adult population.

MATERIAL AND METHODS

Using a stratified random sampling method we enrolled a total of 2799 individuals (1438 from Sari and 1361 from Kerman). The mean age was 33.7 years (range 18-66), with 1398 men. IgA anti-tissue transglutaminase (tTG) and IgA anti-EMA were determined in the serum of all subjects. Those participants with a positive serology for any of the two tests underwent small intestinal biopsy, and were classified according to revised Marsh criteria histologically. A diagnosis of GSE was based on positive serology and a compatible histopathological finding. The maximum likelihood latent class model was used to estimate the sensitivity and specificity of the two tests.

RESULTS

Twenty-nine cases showed positive IgA tTG-Ab (15 men and 14 women, mean age 35.4 years, range 18-59), whereas only five were simultaneously positive for EMA. Except for two subjects with normal small bowel histology (Marsh 0), all other subjects were found to have biopsy findings compatible with GSE: 18 Marsh I, five Marsh II, three Marsh IIIa and one Marsh IIIc lesions. he prevalence of GSE was 0.96% or 1:104. The sensitivity and specificity of the human-recombinant IgA tTG-Ab assay were 100 and 99%, respectively, whereas the results for IgA EMA were 19 and 100%, respectively. The IgA EMA was positive in cases with advanced mucosal lesions of the small bowel. The mean serum value of IgA tTG-Ab was higher in patients with severe enteropathy compared with those showing slight mucosal changes (P<0.05).

CONCLUSION

The minimum prevalence of gluten sensitivity among the general population of northern and southern Iran is 1:104. The best screening test for the detection of GSE in the general population is IgA tTG-Ab.

Diagnosis of celiac disease

Celiac disease is an immune mediated enteropathy initiated by ingestion of gluten, in genetically susceptible individuals. With changing epidemiology, celiac disease initially thought to affect only Europeans, has been increasingly reported from other parts of the world including India. However, its true prevalence in India is still not known, as the diagnosis is being missed. The gold standards for diagnosis have been characteristic small intestinal mucosal changes on gluten and a full clinical remission on its removal from the diet. Presence of serological antibodies, which disappear on gluten free diet further confirms the diagnosis. The understanding of the histopathology of celiac disease has changed over the years. The small bowel mucosal lesion of celiac disease is an evolutionary process with normal mucosal architecture and an increase in intraepithelial lymphocytes at one end of the spectrum and classical flat mucosa at the other. In the Indian subcontinent celiac disease has a heterogeneous histological presentation and the diagnosis may be missed if it is based only on severe mucosal changes or the serology is not considered when moderate or mild mucosal changes are present. The last two decades have shown that antiendomysical (Anti EMA) and anti tissue transglutaminase antibodies (anti-tTGA) have a sensitivity and specificity of more than 95% to diagnose celiac disease. Anti EMA tests being operator dependent are more liable to errors and anti- tTGA may be preferred for large scale screening. However, the different source of tTGA antigen, varied techniques of production and the use of arbitrary units by different commercial kits can influence the diagnostic accuracy of the anti-tTGA assay. There is a strong genetic association of celiac disease with HLA-DQ2 or DQ8. The presence of HLA-DQ2 hetrodimer in more than 97% of a group of North Indian patients with celiac disease indicates that this population has a similar genetic risk for the disease. HLA DQ2 typing can be used for ruling out celiac disease where the diagnosis is equivocal as it has a negative predictive value of greater than 95%. Given the protean clinical manifestation and the heterogeneous histology a standard algorithm for diagnosis of celiac disease is important.

Systematic review: the use of serology to exclude or diagnose coeliac disease (a comparison of the endomysial and tissue transglutaminase antibody tests)

BACKGROUND

With the appreciation of the high prevalence of coeliac disease there is increasing use of serology in screening asymptomatic people and testing those with suggestive features.

AIM

To compare the sensitivities and specificities of the endomysial antibody and the tissue transglutaminase antibody tests.

METHODS

Using electronic databases a search was made for relevant papers using the terms tissue transglutaminase and endomysial antibody.

RESULTS

Both the endomysial antibody and tissue transglutaminase antibody have very high sensitivities (93% for both) and specificities (>99% and >98% respectively) for the diagnosis of typical coeliac disease with villous atrophy. Human recombinant tissue transglutaminase performs much better than guinea pig tissue transglutaminase. Review of studies comparing endomysial antibody with human recombinant tissue transglutaminase antibody shows that endomysial antibody more often has a higher specificity and human recombinant tissue transglutaminase antibody more often has a higher sensitivity.

CONCLUSION

The human recombinant tissue transglutaminase antibody is the preferred test for screening asymptomatic people and for excluding coeliac disease in symptomatic individuals with a low pretest probability (i.e. <25%) for coeliac disease. Furthermore, it has a number of practical and financial advantages. If the pretest probability is >25%, biopsy is preferred as the post-test probability of coeliac disease with a negative test is still >2%.

Prevalence and demographic characteristics of celiac disease among blood donors in Ribeirão Preto, State of São Paulo, Brazil

Celiac disease (CD) is an underdiagnosed disease occurring in different clinical forms. This study aimed to determine the prevalence of CD among blood donors from Ribeirão Preto, Brazil, and to study some demographic characteristics of celiac patients. Blood samples from 3000 blood donors were tested for the presence of tissue transglutaminase antibody and positive samples were tested for endomysial antibody. Donors positive to both tests were referred for clinical evaluation and for a jejunal biopsy. Twenty-four samples were moderately/strongly positive for transglutaminase, with 9 of them being endomysial negative and 15 positive. Of the 13 biopsies obtained from 12 females and 1 male, 1 was classified as Marsh grade IV, 4 as grade III, 2 as grade II, 4 as grade I, and 2 as grade 0. Estimated prevalence was therefore 1:273 (0.33%; 95% CI, 0.127 to 0.539). The 1:273 estimated prevalence of CD detected indicates that the disease is not rare in Brazil. The frequency was higher among females and among individuals of European descent, with a significantly higher frequency for a family history of digestive tract cancer or epilepsy.

Performance of antibodies against tissue transglutaminase for the diagnosis of celiac disease: meta-analysis

A meta-analysis of studies investigating the diagnostic accuracy of enzyme-linked immunosorbent assays (ELISA) for antibodies against tissue transglutaminases (tTG) of various origins in celiac disease (CD) diagnosis was carried out. Twenty-one studies, with untreated CD patients and healthy/CD-free controls, were included in the meta-analysis. The diagnostic accuracy was estimated using a summary receiver operating characteristic (SROC) curve and pooled sensitivity (Se) and specificity (Sp). Multiple assays within a study were treated by considering all the assays within a study and by analyzing the most popular assay (i.e., the commercial anti-tTTG ELISA most frequently utilized in the papers in which multiple assays were included). The SROC curve indicated the absence of heterogeneity, and the superiority of recombinant human tTG (rh-tTG) and purified human tTG (ph-tTG) compared to guinea pig-tTG (gp-tTG). The sensitivities (most popular assay) for rh-tTG, ph-tTG, and gp-tTG were 94%, 90%, and 92%, respectively, and the specificities were 97%, 92%, and 96%, respectively. A sensitivity analysis (exclusion of studies with bias) altered the results of ph-tTG: Se, 95%; Sp, 98%. The sensitivities (all individual assays) for rh-tTG, ph-tTG, and gp-tTG were 94%, 94%, and 91%, respectively, and the specificities were 95%, 94%, and 89%, respectively. Human tTG ELISA is sensitive and specific, and it can be used for mass screening. Sensitivity analysis showed that ph-tTG might perform better.

[Association between serum markers for celiac and thyroid autoimmune diseases]

Celiac disease (CD) is an autoimmune disease of the small bowel characterized by a strong genetic association with HLA - DQ2 and DQ8. Gluten is the etiological factor and the tissue enzyme transglutaminase (TGase) is its autoantigen. CD is associated with several autoimmune diseases such as type 1 diabetes, systemic lupus erythematous, rheumatoid arthritis, Sjögrens syndrome and autoimmune thyroid diseases. The aim of this study was to investigate the occurrence of serum IgA anti-endomysial and anti-human TGase antibodies in individuals with positive anti-thyroid antibody (ATA). The concordance between these two tests was also evaluated. Anti-endomysial antibodies were positive in 10 out of 456 (2.2%) and anti-human TGase were positive in 14 of 454 (3.1%) individuals with positive ATA. In control subjects they were positive in 1 of 197 (0.5%) and 2 of 198 (1%) for anti-endomysial and anti-human tissue TGase antibodies, respectively. The odds ratio (OR) for the anti-endomysial antibodies was 4.42 and for the anti-human TGase 3.12 in individuals with ATA when compared with controls. An elevated concordance index (k= 0.84) was observed between anti-endomisyal antibodies and anti-human TGase. We conclude that the determination of anti-TGase antibodies is a good test for DC screening.

Autoantibodies against soluble and immobilized human recombinant tissue transglutaminase in children with celiac disease

OBJECTIVES

The conformation of tissue transglutaminase might influence the performance of immunoassays to detect autoantibodies from patients with celiac disease. The present study investigated how the exposure of tissue transglutaminase kept in a liquid phase and fixed to a solid support affected the binding of immunoglobulin (Ig)A and IgG autoantibodies in children with untreated and treated celiac disease.

METHODS

Included were 73 untreated celiac disease children, 50 controls and 80 children with treated celiac disease. IgA and IgG antitissue transglutaminase were measured with solid phase enzyme-linked immunoassay (ELISA) and liquid phase radioligand binding assays. For IgG antitissue transglutaminase detection with radioligand binding assays antihuman IgG and protein A were used. IgA endomysial autoantibodies were measured by indirect immunofluorescence.

RESULTS

Both ELISA and radioligand binding assays detected IgA antitissue transglutaminase in 65 of 73 untreated celiac disease children and in 2 of 50 controls. One additional control child was detected with radioligand binding assays. Endomysial autoantibodies were present in 62 of 73 celiac disease children and in 2 of 50 controls. IgG antitissue transglutaminase was detected with both ELISA and radioligand binding assays in 40 of 73 untreated celiac disease children and in 2 of 50 controls. Radioligand binding assays using protein A detected 20 of 73 additional untreated celiac disease children and one control child with increased IgG antitissue transglutaminase. In treated celiac disease children, 21 of 80 were IgA antitissue transglutaminase positive with radioligand binding assays, 3 of 80 with ELISA, whereas none had endomysial autoantibodies.

CONCLUSIONS

No qualitative differences between radioligand binding assays and ELISA in IgA or IgG antitissue transglutaminase binding from untreated celiac disease children was demonstrated. However, discrepancies in the binding of IgA antitissue transglutaminase from a subgroup of treated celiac disease children indicated that alterations of tissue transglutaminase might occur on fixation of the antigen. Protein A used for radioligand binding assays seemed not to assess IgG autoantibodies exclusively. IgA antitissue transglutaminase detection in screening of childhood celiac disease can be performed either by ELISA or radioligand binding assays because the two assays are interchangeable.

Immunoglobulin G (IgG) anti-tissue transglutaminase antibodies used as markers for IgA-deficient celiac disease patients

The role of immunoglobulin A (IgA) anti-tissue transglutaminase antibodies (IgA-tTG) as predictors of untreated celiac disease (CoD) is well documented, and the presence and levels of these antibodies are most accurately monitored with native or recombinant human antigens. However, IgA-deficient CoD patients are not identified by IgA serology, and conflicting results concerning the diagnostic validity of IgG antibodies against gliadin (IgG-AGA), endomysium (IgG-EmA), and tTG (IgG-tTG) have been reported. The aim of the present study was to evaluate the utility of IgG-tTG for the detection of CoD in IgA-deficient patients. Samples from 115 IgA-deficient and 200 IgA-sufficient subjects were collected and tested for the presence of IgA and IgG antibodies against tTG, EmA, and AGA. Antibodies against tTG were measured by an enzyme-linked immunosorbent assay based on recombinant human tTG, and antibodies against EmA were determined by immunofluorescence. The values for IgG-tTG showed a higher correlation (correlation coefficient [r] = 0.91) with those for IgG-EmA for the IgA-deficient subjects than for the IgA-sufficient subjects (r = 0.88). The overall concordance of the positive and negative results between IgG-tTG and IgG-EmA was 97%, and the IgG-tTG assay discriminated between IgG-EmA-positive and -negative subjects with IgA deficiency at a rate of 100%. Elevated levels of IgG-tTG and IgG-EmA were measured in 70% of the IgA-sufficient subjects. IgG-tTG detection with recombinant human tTG is a good alternative to IgG-EmA detection, and the addition of IgG-tTG assessment to present screening methods may improve the ability to identify IgA-deficient subjects with CoD.

The diagnostic accuracy of serologic tests for celiac disease: a systematic review

Clinicians are increasingly utilizing noninvasive serologic tests for the diagnosis and screening of celiac disease (CD). The aim of this study was to conduct a systematic review of the diagnostic performance of serologic tests for the diagnosis and screening of CD. Standard systematic review methodology was used. A literature search was conducted in MEDLINE (1966 to October 2003) and EMBASE (1974 to December 2003) databases. A weighted mean of the sensitivity and specificity along with 95% confidence intervals and summary receiver operating characteristic (ROC) curves were calculated. The pooled specificity of endomyseal antibody (EMA)-monkey esophagus (ME) or EMA-human umbilical cord (HU) was close to 100% in adults and children. The pooled specificity of transglutaminase antibody (tTG)-guinea pig (GP) and tTG-human recombinant (HR) were between 95% and 99%. IgA-EMA-ME demonstrated sensitivities of 96% and 97% in children and adults, respectively. EMA-HU demonstrated a similar sensitivity of 97% in children but 90% in adults. The pooled sensitivity of tTG-GP in adults and children was 90% and 93%, respectively. The sensitivity of tTG-HR was 98% and 96%, respectively. The performance of antigliadin antibody was inferior to that of EMA and tTG. EMA and tTG offer high sensitivity and specificity. The sensitivity of these tests appears to be lower than reported when milder histologic grades are used to define CD (below 90%). If true, the nearly perfect negative predictive value of these tests would drop. The positive predictive value of these tests is likely lower than reported when the tests are applied in low-prevalence populations.

Antitissue transglutaminase and antithyroid autoantibodies in children with Down syndrome and celiac disease

OBJECTIVES

We measured circulating autoantibodies and evaluated the potential of circulating antitissue transglutaminase (tTG) antibodies to determine the presence of celiac disease (CD) in children with Down syndrome.

METHODS

An ELISA based on recombinant human tTG was used to measure the levels of immunoglobulin A and immunoglobulin G antibodies in serum samples from 72 children with Down syndrome, 52 children with biopsy-verified CD, 21 disease controls with a normal small intestinal mucosa and 23 healthy controls. Of the 72 Down syndrome children, 11 under-went a small intestinal biopsy.

RESULTS

Four of 72 children with Down syndrome were diagnosed as having CD and three of them had serum levels of immunoglobulin A tTG antibodies greater than 6 U/mL (668, 147 and 7 U/mL). One Down syndrome child with biopsyproven CD had normal levels of immunoglobulin A tTG. Two Down syndrome children had increased levels of immunoglobulin A tTG (13 and 7 U/mL) but none of these children had an intestinal biopsy performed. Of the 52 CD subjects (median 664 U/mL) one was negative for immunoglobulin A tTG (5 U/mL) and all healthy controls (median 1.2 U/mL) and disease controls (median 0.9 U/mL) had immunoglobulin A tTG antibody levels less than 6 U/mL. Two of four Down syndrome children with CD and 36 of 52 celiac children had increased serum levels of immunoglobulin G tTG antibodies. There was no correlation between the serum levels of tTG and antithyroid autoantibodies.

CONCLUSIONS

Although the diagnosis of CD depends on histologic evaluation of intestinal biopsies, detection of anti-tTG antibodies provides a useful complementary diagnostic method for CD in children with Down syndrome.

Antibody levels in adult patients with coeliac disease during gluten-free diet: a rapid initial decrease of clinical importance

OBJECTIVE

Analysis of antibodies against tissue transglutaminase (tTG) has been shown valuable in the diagnosis of coeliac disease (CD) but how quickly serum titres decrease after introduction of a gluten-free diet (GFD) is not known in adults. CD is a well-recognized disorder amongst the general population and many persons try a GFD for fairly vague symptoms before they seek medical advice. Therefore, it is important to determine the time that the serologic tests remain predictive of the disease after the introduction of a GFD.

METHODS

Sera were taken from 22 consecutively biopsy-proven adult patients with CD in connection with the diagnostic biopsy. The patients were followed for 1 year and sera were taken after 1, 3, 6 and 12 months after start of a GFD. Sera were stored at -20 degrees C and analysed for IgA antibodies against gliadin, endomysium and two different commercial tTG assays based on recombinant human tTG (tTGrh) and guinea-pig liver (tTGgp).

RESULTS

Twenty patients could be followed during GFD and all antibody titres fell sharply within 1 month after introduction of a GFD and continued to decline during the survey interval. Thirty days after beginning the diet only 58, 84, 74 and 53% of all patients had positive antibody levels of tTGrh, tTGgp, EmA and AGA respectively.

CONCLUSIONS

As the antibodies used to confirm the diagnosis of CD fall rapidly and continue to decline following the introduction of a GFD, it is important that health care providers carefully inquire about the possibility of self-prescribed diets before patients sought medical attention.

Epitopes recognised by tissue transglutaminase antibodies in coeliac disease

The interaction between IgA tissue transglutaminase (tTG) antibodies (Abs) and 35S-labelled tTG produced in a transcription/translation (TnT) system with various amino acid (aa) deletions has been studied. These experiments showed that the tTG N-terminal aa 1-89 were important for tTG Ab binding in all 15 coeliac disease sera studied and the central residues (aa 401-491) were important for binding of tTG Abs in all but one sera. The contribution of C-terminal residues to tTG Ab binding varied in different coeliac sera but overall was less than the contributions of the N terminal and central regions. Mouse monoclonal antibodies (MAbs) to tTG were produced and the tTG aa sequences recognised by the MAbs determined using modified 35S-labelled tTG proteins. Analysis of the inhibiting effects of patient sera tTG Ab on binding of tTG MAbs to tTG confirmed the importance of the N-terminal and central regions of tTG in forming serum tTG Ab binding sites. Recombinant human tTG was expressed in yeast and purified to better than 95% homogeneity using MAb affinity chromatography as a final purification step. This material was highly suitable for use in an ELISA for tTGAb.

Diagnostic Accuracy of Ten Second-Generation (Human) Tissue Transglutaminase Antibody Assays in Celiac Disease

Background: Anti-tissue transglutaminase (tTG) assays that use human tTG as antigen have recently become available. We evaluated commercially available assays with human tTG antigen to estimate their diagnostic accuracies and to determine whether they agree sufficiently to be used interchangeably.

Methods: Ten commercially available second-generation anti-tTG assays were evaluated. The following populations were studied: celiac disease (CD) patients at the time of diagnosis without (n = 70) or with (n = 5) IgA deficiency; diseased controls (n = 70); and CD patients without (n = 28) or with (n = 2) IgA deficiency during follow-up. All individuals included in the study underwent intestinal biopsy. Technical performance (linearity, interference, precision, correlation, and agreement) and diagnostic accuracy (sensitivity and specificity) were compared. Anti-gliadin and anti-endomysium antibodies were also measured.

Results: IgA anti-tTG results correlated well overall, but numerical values differed. Diagnostic sensitivity ranged between 91% and 97% and specificity between 96% and 100%. These were higher than the sensitivity and specificity of the IgA endomysium assay and the IgA gliadin assay. Generally, IgG anti-tTG was less sensitive but more specific than IgG anti-gliadin for the diagnosis of CD in the small group of IgA-deficient patients.

Conclusions: Overall diagnostic performance of IgA tTG assays is acceptable and comparable among the different assays, but numerical values differ. Standardization is needed.

Immunochromatographic sticks for tissue transglutaminase and antigliadin antibody screening in celiac disease

BACKGROUND & AIMS

We investigated two 1-step immunochromatographic visual assays based on human recombinant tissue-transglutaminase (t-TG) as an alternative to enzyme-linked immunosorbent assays (ELISAs) for celiac disease (CD) screening.

METHODS

We used a tissue-transglutaminase (t-TG) stick, which detected immunoglobulin A/G (IgA/G) antibodies to t-TG, and a t-TG/antigliadin antibodies (AGA) stick, which detected IgA antibodies to both t-TG and AGA, as well as t-TG and AGA ELISAs, to determine t-TG and AGA antibodies in untreated celiac patients with subtotal villous atrophy. A total of 142 children (3 IgA-deficient sera) and 30 adults, and 140 controls (normal mucosa; 121 children and 19 adults), plus 23 sera from pediatric CD patients in remission were assayed.

RESULTS

For pediatric patients, with the t-TG stick we obtained a sensitivity of 97.1% and a specificity of 99.0%, and in adults, 83.3% and 100%, respectively. The t-TG/AGA stick displayed a sensitivity of 95.7% and a specificity of 99.0% for t-TG and a sensitivity of 89.2% and a specificity of 95.8% for AGA in children, and a sensitivity of 80% and a specificity of 100% for t-TG and a sensitivity of 83.3% and a specificity of 100% for AGA in adults. Results were comparable with the corresponding ELISAs.

CONCLUSIONS

The 2 visual assays are efficient for CD screening as an alternative to ELISAs. They are simple to handle and to interpret. By the combined use of the 2 sticks, IgA-deficient patients can be identified as positive in the t-TG (IgG/A) but negative in the t-TG/AGA (IgA) stick.

Autoantibodies in the diagnosis and management of liver disease

Autoantibodies are nonpathogenic manifestations of immune reactivity, and they may occur in acute and chronic liver diseases. Autoantibodies may be consequences rather than causes of the liver injury, and they should be regarded as diagnostic clues rather than etiologic markers. Conventional autoantibodies used in the categorization of autoimmune liver disease are antinuclear antibodies, smooth muscle antibodies, antibodies to liver/kidney microsome type 1, antimitochondrial antibodies, and atypical perinuclear anti-neutrophil cytoplasmic antibodies. Ancillary autoantibodies that enhance diagnostic specificity, have prognostic connotation, or direct treatment are antibodies to endomysium, tissue transglutaminase, histones, doubled-stranded DNA, and actin. Autoantibodies that have an emerging diagnostic and prognostic significance are antibodies to soluble liver antigen/liver pancreas, asialoglycoprotein receptor, liver cytosol type 1, and nuclear pore complex antigens. Autoantibodies of uncertain clinical value that remain under investigation are antibodies to chromatin, lactoferrin, and Saccharomyces cervisiae. Continued recognition and characterization of autoantibodies should improve diagnostic precision, provide prognostic indices, and elucidate target autoantigens. These advances may in turn clarify pathogenic mechanisms, facilitate the development of animal models, and generate novel site-specific therapies.

Fluctuating transglutaminase autoantibodies are related to histologic features of celiac disease

BACKGROUND & AIMS

Asymptomatic children at risk for celiac disease (CD) and seropositive for immunoglobulin A anti-TG autoantibodies (TGAA) may lack small intestinal mucosal changes characteristic of CD. We have followed a group of children with serial testing for TGAA.

METHODS

Subjects were a group of at-risk children comprised of infants expressing HLA-DR3 on newborn screening, those with type 1A diabetes, or a first-degree relative of someone with type 1 diabetes. All children participating in the prospective study for development of CD underwent serial testing for TGAA. Data from clinical evaluation and small intestinal biopsy were compared to the TGAA levels followed over time.

RESULTS

In 42 children, serial TGAA determinations while on a gluten-containing diet showed levels fluctuating 10-100-fold over 3-12 months. A TGAA index more than 0.5 had a positive predictive value (PPV) for histologic confirmation of CD of 96% (22/23). A TGAA index above the usual cutoff for positivity (0.05) had a PPV of only 76% (28/37).

CONCLUSIONS

In children with TGAA seropositivity, the TGAA level varied over time and a higher titer predicted an abnormal biopsy characteristic of CD. A threshold for biopsy for diagnosis of CD could be set higher for screening-identified cases than for clinically identified cases to decrease the frequency of performing "normal" biopsies.

Advances in celiac disease

In recent years, it has become evident that CD is much more common than previously appreciated, with a prevalence of 0.5% to 1% in Western, Arabian, and Indian populations. The disease may be present without symptoms (silent CD) or may present with extraintestinal manifestations only. Increasing awareness of the many faces of CD will increase diagnosis rate. CD patients have a cure for their disease, named the gluten-free diet, but this curative measure is very hard to adhere to. With the new insights into the pathogenesis of CD, clinicians enter an era where new treatment modalities for CD may turn into reality.

A comparison of antibodies to tissue transglutaminase with conventional serological tests in the diagnosis of coeliac disease

BACKGROUND

Tissue transglutaminase is now recognized as the autoantigen for antiendomysial antibodies. Antibodies to tissue transglutaminase have been proposed as a valuable test for coeliac disease.

OBJECTIVE

To determine the value of antibodies to tissue transglutaminase in the diagnosis of coeliac disease in our outpatient population.

METHODS

Patients who underwent serological tests for coeliac disease during the first 18 months of the tissue transglutaminase antibody assay were retrospectively identified from the regional serology laboratory database. Patients' symptoms were noted, along with serological results and duodenal histology in those patients who underwent duodenal biopsy. RESULTS In total, 586 patients were identified as having been serologically tested for coeliac disease, of whom 92 patients (33 men; mean age 51.7 years) had been followed up with duodenal biopsies. Of these 92 patients, 29 (31%; 14 men; mean age 52.5 years) had histological features of coeliac disease. The 63 patients with normal histology (19 men; mean age 51.8 years) acted as controls. Weight loss was more frequent in coeliac disease patients compared to controls (7 vs 5; P = 0.04) whereas the frequency of anaemia (P = 0.85) and diarrhoea (P = 0.74) did not differ significantly between the two groups. The sensitivity and specificity of tissue transglutaminase antibodies (86%; 84%) were compared to those for antiendomysial antibodies (90%; 98%) and antigliadin antibodies (76%; 79%).

CONCLUSIONS

The diagnostic value of tissue transglutaminase antibodies was intermediate between that of antiendomysial antibodies and antigliadin antibodies. However, duodenal biopsy remains the gold standard diagnostic test for coeliac disease.

The role of antitissue transglutaminase assay for the diagnosis and monitoring of coeliac disease: a French-Italian multicentre study

AIMS

Tissue transglutaminase (tTG) was recently identified as the major autoantigen in coeliac disease. The aim of this multicentre study was to evaluate the impact of a new immunoenzymatic assay for the detection of IgA anti-tGT antibodies.

METHODS

Seventy four Italian and French clinical laboratories participated in this study; anti-tTG IgA with an enzyme linked immunosorbent assay (ELISA) method using guinea pig liver extract as the coating antigen, anti-endomysium IgA autoantibodies (EMA), and total serum IgA were determined in 7948 patients, 1162 of whom had coeliac disease (737 untreated cases and 425 on a gluten free diet). A proportion of the sera were then sent to a reference laboratory for anti-tTG retesting with an ELISA method using recombinant human tTG antigen.

RESULTS

Seven thousand four hundred and fifty eight (93.8%) sera were EMA/antiguinea pig tTG concordant (positive or negative); 490 (6.2%) were non-concordant. The sensitivity of EMA and antiguinea pig tTG in the 737 untreated patients with coeliac disease was 92.1% and 94.8%, respectively, and the specificity was 99.8% and 99.2%, respectively. Retesting of the discordant sera showed that of the 162 sera classified as EMA negative/antiguinea pig tTG positive, only 49 were positive for human recombinant anti-tTG, and that 39 of these were also EMA positive. Furthermore, of the 36 sera classified as EMA positive/antiguinea pig tTG negative, only two were confirmed as EMA positive.

CONCLUSIONS

The antiguinea pig tTG assay is more sensitive but less specific than EMA, whereas the antihuman recombinant tTG assay is far more specific and just as sensitive as antiguinea pig tTG. Testing for EMA presents considerable interpretative problems and is difficult to standardise.

Production of recombinant human tissue transglutaminase using the baculovirus expression system, and its application for serological diagnosis of coeliac disease

BACKGROUND AND OBJECTIVES

Tissue transglutaminase was identified as the main autoantigen in coeliac disease (CD) but enzyme immunoassays applying the commercially available antigen from guinea pig liver show insufficient specificity and sensitivity for diagnosis as compared with endomysium antibodies (EmA). The aim of this present study was to develop a new method for the cloning and expression of human tissue transglutaminase (hu-tTG) and to test hu-tTG in the serological diagnosis of CD.

METHODS

Hu-tTG was cloned and expressed using a baculovirus system and SF9 insect cells. The enzyme carried a C-terminal His tag allowing efficient affinity purification from cell lysates. The recognition of hu-tTG by human sera was checked by using an enzyme linked immunosorbent assay (ELISA). For this, 35 patients with active CD were compared with 144 controls (18 patients with bioptically excluded CD, 89 blood donors, 30 patients with inflammatory bowel disease, and seven patients with cystic fibrosis).

RESULTS

The ELISA using hu-tTG showed a sensitivity of 100% and a specificity of 98.6%. Titres of antibodies against hu-tTG (anti-hu-tTG) were positively correlated with EmA titres. All results negative for EmA were also negative for anti-hu-tTG. There were, however, EmA positive results up to a titre of 1 : 80 below the cut-off for anti-hu-tTG. For comparison, antibodies against guinea pig tissue transglutaminase (anti-gp-tTG) were determined in parallel. All patients with anti-hu-tTG below the cut-off were also negative for anti-gp-tTG. However, there were eight patients positive for anti-hu-tTG but negative for anti-gp-tTG.

CONCLUSIONS

The new test reaches and even exceeds diagnostic efficiency of EmA for coeliac diagnosis.

The use of a single serological marker underestimates the prevalence of celiac disease in Israel: a study of blood donors

OBJECTIVES

Recent studies suggest that celiac disease was previously underdiagnosed. To find out whether antiendomysial antibodies underestimate the prevalence of celiac disease, we elected to use a strategy combining multiple serological markers to explore the prevalence of celiac disease in Israel and the usefulness of the various antibodies in screening for celiac disease.

METHODS

Serum samples from 1571 healthy blood donors were tested. A small intestinal biopsy was offered to all patients who tested positive for either human tissue transglutaminase antibodies, an ELISA kit based on antiendomysium (EMA-ELISA), immunoglobulin A antigliadin verified by antiendomysial immunofluorescence antibodies, and to patients who were IgA deficient with elevated antigliadin IgG.

RESULTS

A total of 59 subjects (3.8% of study population) were offered an intestinal biopsy based on serological findings, and 30 of 59 patients agreed to undergo intestinal biopsy (1.9% of study population). Celiac disease was diagnosed in 10 patients, establishing a prevalence of at least 1:157 in the general population (0.6%, CI = 0.3-1.1%). Using any serological marker alone would have underestimated the prevalence of celiac disease, as it was diagnosed in only two patients who tested positive for endomysial immunofluorescence antibodies (prevalence of 1:786, 0.1%, CI = 0.02-0.5%), six patients positive for tissue transglutaminase (prevalence of 1:262, 0.4%, CI = 0.1-0.9%), and seven patients positive for ELISA-EMA (prevalence of 1:224, 0.45%, CI = 0.2-0.9%).

CONCLUSIONS

The prevalence of celiac disease in Israel is at least 1:157 in the general population, confirming its underdiagnosis in previous studies. The disparity between the various serological markers suggest that the use of one serological marker is insufficient for establishing the true prevalence of celiac disease.

Diagnostic value of anti-Saccharomyces cerevisiae and antineutrophil cytoplasmic antibodies for inflammatory bowel disease: high prevalence in patients with celiac disease

Both celiac disease and inflammatory bowel disease (IBD) are characterized by chronic diarrhea and the presence of distinct (auto)antibodies. In the present study we wanted to determine the prevalence of serological markers for inflammatory bowel disease, i.e., perinuclear antineutrophil cytoplasmic antibodies (pANCA) and/or anti-Saccharomyces cerevisiae antibodies (ASCA), in 37 patients with biopsy-confirmed celiac disease (Marsh IIIb/c). The majority of the patients was positive for IgA (auto)antibodies typically associated with celiac disease, i.e., antiendomysium antibodies (EMA) (86.5%), antigliadin antibodies (AGA) (73%), and antirecombinant human tissue transglutaminase antibodies (rh-tTGA) (86.5%). Four patients with selective IgA deficiency could be identified by analyzing EMA, AGA, and rh-tTGA for the IgG isotype. The prevalence of pANCA and ASCA, markers that are used for IBD, was unexpectedly high in our cohort of patients with celiac disease: 8 patients were positive for pANCA (IgG) and 16 patients were positive for ASCA (IgG and/or IgA). These results indicate that the presence of pANCA or ASCA in the serum of patients with chronic diarrhea does not exclude celiac disease. A prospective study is required to determine whether pANCA and/or ASCA identify patients at risk for developing secondary autoimmune disease.

Comparison of Anti-Transglutaminase ELISAs and an Anti-Endomysial Antibody Assay in the Diagnosis of Celiac Disease: A Prospective Study

Background: Most studies of anti-transglutaminase (anti-tTG) assays have considered preselected groups of patients. This study compared the sensitivity, specificity, and predictive value of an immunofluorescence method for anti-endomysial antibodies (EmAs) and two anti-tTG ELISAs, one using guinea pig tTG (gp-tTG) and the other human tTG (h-tTG) as antigen, in consecutive patients investigated for suspected celiac disease (CD).

Methods: We studied 207 consecutive patients (99 men, 108 women; age range, 17–84 years) who underwent intestinal biopsy for suspected CD. Patients presented with one or more of the following: weight loss, anemia, chronic diarrhea, abdominal pain, dyspepsia, alternating bowel habits, constipation, pain in the joints, and dermatitis. At entry to the study, an intestinal biopsy was performed and a serum sample was taken for IgA EmAs, anti-gp-tTG, and anti-h-tTG.

Results: Intestinal histology showed that 24 patients had partial or total villous atrophy; in these patients the diagnosis of CD was confirmed by follow-up. The remaining 183 patients had villous/crypt ratios that were within our laboratory’s reference values and were considered controls. Serum EmAs, anti-gp-tTG, and anti-h-tTG were positive in all 24 CD patients; in the control group, none were positive for serum EmAs, but 15 of 183 (8.2%) were positive for anti-gp-tTG, and 6 of 183 (3.3%) were positive for anti-h-tTG. Sensitivity was 100% for all assays, whereas specificity was 100% for the EmA, 92% for the anti-gp-tTG, and 97% for the anti-h-tTG assay. The negative predictive value was 100% for all assays; the positive predictive value was 100% for the EmA, 80% [95% confidence interval (CI), 65–95%] for the anti-h-tTG (P = 0.03 vs EmA) and 60% (95% CI, 44–76%) for the anti-gp-tTG assay (P = 0.0002 vs EmA). Areas (95% CIs) under the ROC curves were 0.987 (0.97–1.0) for anti-h-tTG and 0.965 (0.94–0.99) for anti-gp-tTG. Most of the patients testing false positive for anti-tTG had Crohn disease or chronic liver disease.

Conclusions: Although both anti-tTG ELISAs showed optimum sensitivity, their lack of specificity yielded positive predictive values significantly lower than those for the EmA assay.

A comparison of 13 guinea pig and human anti-tissue transglutaminase antibody ELISA kits

AIMS

Tissue transglutaminase (tTG) is a major autoantigen recognised by IgA anti-endomysial antibodies (IgA EMA). Enzyme linked immunosorbent assays (ELISA) for IgA anti-tissue transglutaminase antibodies (IgA tTG) have therefore been developed as an alternative serological screening test to IgA EMA for coeliac disease (CD). The use of human tTG (h-tTG), as opposed to guinea pig liver tTG (gpl-tTG), in these assays has been reported to produce superior results. This study compared 13 commercial IgA tTG ELISA kits to ascertain their performance characteristics in the diagnosis of CD in patients with biopsy confirmed disease compared with controls. All patients and controls were adults aged 21 years or older.

METHODS

Sera from the following groups of patients were tested in each kit: (1) 49 patients with CD confirmed on small bowel biopsies (all IgA EMA positive); (2) 34 patients with small bowel biopsies that were not consistent with CD; and (3) 30 patients with biopsy confirmed inflammatory bowel disease. All controls were negative for IgA EMA and were not IgA deficient. Sensitivities and specificities were determined using both the manufacturers' recommended cut off points and receiver operating characteristic (ROC) analysis derived decision thresholds. The area under the curve (AUC) for each ROC plot was also calculated and compared between kits.

RESULTS

In general, the h-tTG based IgA tTG ELISA kits demonstrated superior performance (especially specificity) compared with the gpl-tTG based kits, although 100% sensitivity and specificity (comparable to the IgA EMA assay) was obtained in only one recombinant h-tTG based kit.

CONCLUSIONS

The use of h-tTG in IgA tTG ELISA kits is generally, but not universally, associated with superior performance. Factors other than antigen source are important in determining kit performance.

Recombinant human tissue transglutaminase for diagnosis and follow-up of childhood coeliac disease

Highly discriminatory markers for celiac disease are needed to identify children with early mucosal lesions and for rapid follow-up. The aim of this study was to evaluate the potential of circulating anti-tissue transglutaminase (tTG) IgA and IgG antibodies in the diagnosis and follow-up of childhood celiac disease. An ELISA using recombinant human tTG was used to measure the levels of IgA and IgG anti-tTG antibodies in 226 serum samples from 57 children with biopsy-verified celiac disease, 29 disease control subjects, and 24 healthy control subjects. All samples were also analyzed for anti-endomysium antibodies (EMA). The levels of IgA and IgG anti-tTG antibodies correlated with the condition of the small intestinal villous structure and the serum levels of IgA EMA. All of the 25 serum samples obtained from untreated patients contained IgA anti-tTG antibodies, and 24 of 25 also had IgA EMA. Of the serum samples from 53 control children, two had IgA anti-tTG antibodies and two had IgA EMA. Children younger than 5 y of age with untreated celiac disease had the highest serum levels of both IgA and IgG anti-tTG. There was already an increase in IgA anti-tTG antibodies after 2 wk of gluten challenge (p < 0.01). Although the criteria-based diagnosis of childhood celiac disease still depends on histologic evaluation of intestinal biopsies, detection of anti-tTG antibodies provides useful complementary diagnostic information. The human recombinant tTG-based ELISA can be used as a sensitive and specific test to support the diagnosis and may also be used in the follow-up of treatment in childhood celiac disease.

Celiac Disease

Individuals with celiac disease present with a wide array of symptoms and signs. Celiac disease can result in substantial injury to the small intestine, deleterious effects on other organ systems, and an overall doubling of mortality. The role of the gastroenterologist is primarily to make the diagnosis and then to ensure that patients with celiac disease receive up-to-date and accurate instructions on diet. It is our opinion that gastroenterologists should participate in the follow-up of what is in fact a form of inflammatory bowel disease. The failure to identify and treat patients with substantial problems may result in an excess of preventable morbidity and mortality. Intestinal biopsy is the definitive method of making the diagnosis of celiac disease, provided the patient has not excluded gluten from his or her diet, because exclusion of gluten results in negative serologic test results and normal small intestinal biopsy samples. The removal of gluten from the diet can result in a total recovery of gut function and a correction of most other consequences. The response is usually so complete that patients should consider themselves to be basically healthy as long as they stay away from the offending foods. However, the execution and maintenance of the "theoretically simple" exclusion of gluten is difficult. The condition is permanent and mandates adherence to a lifelong gluten-free diet; even small amounts of gluten can result in injury to the intestinal lining. The diet is restrictive and requires the patient to be careful about food choices. Therefore, patient education and motivation are crucial to a successful outcome. The correction of vitamin and mineral deficiencies may be helpful in aiding recovery; vitamin D and calcium supplementation often is recommended. No drug therapy has been proven to suppress the disease.

Tissue transglutaminase and endomysial autoantibodies measured in an historical cohort of children and young adults in whom coeliac disease was suspected

OBJECTIVE

To evaluate whether anti-endomysial and anti-transglutaminase antibodies are relevant important markers of coeliac disease in an historical group of patient sera.

DESIGN

Sera from 196 children suspected to suffer from coeliac disease were analysed for these antibodies.

METHODS

A total of 233 serum samples were obtained simultaneously with a biopsy. Coeliac disease was confirmed in 37 (19%) patients. Antibodies against guinea pig transglutaminase were determined by enzyme-linked immunosorbent assay (ELISA); endomysial antibodies were determined by immunofluorescence.

RESULTS

In 17 samples, immunoglobulin A (IgA) anti-transglutaminase levels were increased; 16 of these came from coeliac patients. High levels correlated with high prediagnostic or challenge-related gluten intake. The additional anti-transglutaminase-positive patient was assumed to suffer from sequelae to gastroenteritis.

CONCLUSIONS

Raised IgA anti-transglutaminase levels were correlated with presence of coeliac disease. Negative tests were seen in some coeliac patients when on a gluten-containing diet. The IgA anti-transglutaminase test using guinea pig antigen was less sensitive than anti-endomysial antibodies but rather specific for active coeliac disease. In our study, anti-endomysial antibodies were more specific than anti-transglutaminase antibodies for active coeliac disease.

Do you still need a biopsy to diagnose celiac disease?

Celiac disease is a common and permanent condition caused by an abnormal immune response to ingested gluten in genetically susceptible individuals. Its proper diagnosis is very important even in patients presenting with mild symptoms because severe and debilitating complications may occur in celiac patients not following a strict gluten-free diet. In the past several years, important progress has been made not only in our understanding of the pathogenesis of this condition but also in the availability of tools to screen it. Antigliadin antibodies, once largely used for this purpose, have been basically replaced by the more costly but far more accurate antiendomysium antibodies. More recently, the enzyme-linked immunosorbent assay (ELISA), which measures the antibodies directed against the autoantigen responsible for the disease (tissue transglutaminase), has also been developed and tested as a screening tool. Currently, however, the poor positive predictive value of this test does not allow practitioners to diagnose celiac disease without the duodenal biopsy showing the typical morphologic changes.

Screening for adult coeliac disease - which serological marker(s) to use?

OBJECTIVE

To determine which serological marker(s) to use when screening for coeliac disease.

DESIGN

In a population-based cross-sectional study we compared the use of antigliadin antibodies (AGA) of isotypes IgA and IgG, antiendomysial antibodies (AEA) of isotype IgA and antitransglutaminase antibodies (ATGA) of isotype IgA for detecting coeliac disease amongst adults.

SETTING

Northern Sweden.

SUBJECTS

A total of 1850 of 2500 (74%) invited adults (aged 25-74 years) who were randomly selected from the population register after stratification for age and sex.

MAIN OUTCOME MEASURES

The sensitivity, specificity and predictive values of the AGA, ATGA and AEA tests.

RESULTS

Nine cases of biopsy proven, previously undiagnosed coeliac disease were detected by screening. The sensitivity of both ATGA and AEA was 100% whilst AGA IgA and IgG both had a sensitivity of 89%. The AEA test had a specificity of 100% whereas the specificities of the ATGA, AGA IgA and IgG tests were 97, 96 and 78%, respectively. The positive predictive value for the AEA test was 100%, whereas it was considerably lower for the other tests (ATGA > AGA IgA > AGA IgG), with further decreases for all tests when shifting from a clinical to a screening situation.

CONCLUSIONS

When screening for coeliac disease we suggest a serial testing approach, i.e. an initial ATGA test and, when positive, followed by an AEA test, provided that IgA deficiency has been excluded. However, assessment of the small intestinal mucosal morphology is still required to ascertain the diagnosis.

The serum IgA class anti-tissue transglutaminase antibodies in the diagnosis and follow up of coeliac disease. Results of an international multi-centre study. International Working Group on Eu-tTG

OBJECTIVES

So far the reliability of the anti-tissue transglutaminase (anti-tTG) test for the diagnosis of coeliac disease has mostly been evaluated using slightly different enzyme-linked immunosorbent assays (ELISAs) in selected and usually small groups of patients. The aims of this study were: (1) to evaluate the reliability of the IgA anti-tTG antibodies for the diagnosis of coeliac disease; and (2) to define the sensitivity and specificity of a commercially available kit for the anti-tTG antibodies' quantitative determination.

DESIGN

Each centre in this international multi-centre study collected sera from three groups of subjects: coeliac disease patients at the onset of (1) or on a gluten-free diet for at least 12 months (2); disease and healthy controls (3).

METHODS

The anti-tTG antibodies were determined in duplicate using an ELISA-based commercially available kit (Eu-tTG Eurospital, Trieste, Italy).

RESULTS

The following overall cases and controls have been enrolled: (1) 399 subjects with active coeliac disease; (2) 351 treated coeliac disease cases; (3) 432 controls. The centralized re-testing was performed on: (1) group a: 176 patients with active coeliac disease (mean anti-tTG, 21 arbitrary units [AU]); (2) group b: 172 treated coeliac disease cases (mean anti-tTG, 5 AU); (3) group c: 206 controls (mean anti-tTG, 3 AU). In active coeliacs, the anti-tTG antibodies showed a significant progressive decrease with age, while in controls an opposite trend was found. In active coeliac disease patients, the anti-tTG antibodies were significantly higher in coeliacs with a grade III enteropathy than in those showing a grade II lesion. In treated coeliacs, the mean anti-tTG values were significantly lower in patients strictly adhering to a gluten-free diet than in those reporting dietary transgressions. The sensitivity and the specificity of the Eu-tTG assay were 90% and 96%, respectively.

CONCLUSION

The results of this study show that the commercially available test for the anti-tTG antibodies' determination is a reproducible and valuable tool for the diagnosis and follow up of coeliac disease.