Anti-transglutaminase antibodies and coeliac disease

[Serological screening of relatives of celiac disease patients: antiendomysium antibodies, anti-tissue transglutaminase or both?]

BACKGROUND

Celiac disease is the most common intestinal disorder of caucasian populations and presents a prevalence of 8% to 18% between the relatives of patients. The anti-endomysial (IgA-EmA) and anti-tissue transglutaminase antibodies (IgA-tTG) have represented an important non invasive and sensitivity method of screening and diagnosis of celiac disease in risk groups and populations.

AIM

To investigate the prevalence of IgA-EmA and IgA-tTG antibodies in relatives of celiac patients and verify the degree of concordance between them.

METHODS

One hundred and seventy seven relatives of celiac patients (76(feminino); 101(masculino); 2-79 years) and 93 healthy individuals were evaluated (34(feminino); 59(masculino); 2-71 years). IgA-EmA were detected by indirect immunofluorescence, with human umbilical cord as substrate, while anti-IgA-tTG titers were measured by enzyme-linked immunosorbent assay (ELISA), using commercial kit.

RESULTS

Total positivity to antibodies in relatives of celiac patients was of 21% (37/177), and showed significant difference compared to control group (0%; 0/93). Twelve percent (21/177) of celiac disease relatives were positive to IgA-EmA, 13.56% (24/177) to IgA-tTG, and 4.52% (8/177) to both assays simultaneously. The concordance between both methods was 83.6% (148/177) and the discordance was 16.4% (29/177), with a positive and significant correlation (r = 0.435). Among the concordant results, 79.1% (140/177) were negative and 4.52% (8/177) were positive to both antibodies. Among the discordant results, 7.34% (13/177) were positive to IgA-EmA and negative to IgA-tTG, while 9.04% (16/177) were negative to IgA- EmA and positive to IgA-tTG.

CONCLUSION

Although the high positivity to IgA-EmA and IgA-tTG emphasizes the importance of the serological screening in relatives of celiac patients, the discordances detected in this study showed that the use of only one method can lead to false negative results. Consequently these relatives will not be submitted to intestinal biopsy to confirm the diagnosis of celiac disease, and to the correct and earlier treatment.

A new indirect chemiluminescent immunoassay to measure anti-tissue transglutaminase antibodies

OBJECTIVES

Anti-tissue transglutaminase antibody (anti-tTG) determination using second-generation (human antigen) enzyme-linked immunoassays (ELISAs) is a very accurate test to diagnose celiac disease (CD). In this study, we compared 2 second-generation ELISAs (Celikey tTG; Pharmacia Diagnostics GmbH & Co, Freiburg, Germany, and QuantaLite; Inova Diagnostics, San Diego, CA) and antiendomysial antibodies (EMAs) with a new indirect chemiluminescence immunoassay (LIAISON tTG; DiaSorin S.p.A., Saluggia, Italy) in diagnosing and monitoring CD in children.

PATIENTS AND METHODS

Antiendomysial antibodies, anti-tTGs and total immunoglobulin A were measured in the sera of 103 control children, 101 children with histologically proven CD and 31 CD children on gluten-free diet (GFD).

RESULTS

Anti-tissue transglutaminase antibody mean levels were significantly higher in CD with respect to control or GFD children. The sensitivity value of EMAs, LIAISON tTG, Celikey tTG and QuantaLite in diagnosing CD was 97.7%, 97.0%, 94.1% and 98.0%, respectively, and the corresponding specificity values were 91.1%, 98.1%, 97.1% and 96.1%, respectively. The degree of mucosal destruction (Marsh criteria) was correlated with EMA semiquantification (P < 0.01) and with the circulating levels of anti-tTGs measured using LIAISON (P < 0.05) or QuantaLite (P < 0.01). Twenty-six CD children were followed up from 5 to 25 months after GFD. The circulating levels of anti-tTGs measured with any of the 3 assays significantly dropped after GFD.

CONCLUSIONS

Anti-tissue transglutaminase antibody determination with second-generation ELISAs is as effective as EMAs for CD diagnosis. The novel chemiluminescent method described in the present paper for the detection of anti-tTGs in the diagnosis of CD had the highest sensitivity and specificity values. The anti-tTG test correlates with the degree of mucosal destruction and is suitable for verifying patient compliance to dietary treatment.

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.

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.

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-associated autoimmune endocrinopathies

Celiac disease (CD) is an autoimmune disorder induced by gluten intake in genetically susceptible individuals. It is characterized by the presence of serum antibodies to endomysium, reticulin, gliadin, and tissue transglutaminase. The incidence of CD in various autoimmune disorders is increased 10- to 30-fold in comparison to the general population, although in many cases CD is clinically asymptomatic or silent. The identification of such cases with CD is important since it may help in the control of type I diabetes or endocrine functions in general, as well as in the prevention of long-term complications of CD, such as lymphoma. It is believed that CD may predispose an individual to other autoimmune disorders such as type I diabetes, autoimmune thyroid, and other endocrine diseases and that gluten may be a possible trigger. The onset of type I diabetes at an early age in patients with CD, compared to non-CD, and the prevention or delay in onset of diabetes by gluten-free diet in genetically predisposed individuals substantiates this antigen trigger hypothesis. Early identification of CD patients in highly susceptible population may result in the treatment of subclinical CD and improved control of associated disorders.

Comparison of ELISA for tissue transglutaminase autoantibodies with antiendomysium antibodies in pediatric and adult patients with celiac disease

BACKGROUND

Tissue transglutaminase (t-TG) is the main autoantigen recognized by the endomysium antibodies (EMA) observed in patients with celiac disease (CD). The aim of the study was to assess an ELISA method for t-TG antibodies (t-TGA) with respect to EMA IF assay in pediatric and adult patients.

METHODS

t-TGA were analyzed by ELISA in 220 sera samples: 82 patients with biopsy-proven untreated CD (23 adults and 59 children), 14 CD children on gluten-free diet, 18 asymptomatic relatives of CD patients, and 106 age-matched control patients with gluten-unrelated gastrointestinal diseases (58 adults and 48 children). Serum IgA EMA were tested on umbilical cord sections in all patients.

RESULTS

The great majority (92.7%) of untreated CD patients (both adults and children) were t-TGA positive (values ranging from 20.1 to > 300 AU). None of the child control patients and only two out of 58 (3.4%) of the adults with unrelated gastrointestinal diseases had serum t-TGA positivity; two out of 18 first-degree relatives with biopsy-proved silent CD were t-TGA (as well as EMA) positive. Finally, two out of 14 CD children, assuming a gluten-free diet, had serum t-TGA (as well as EMA). A highly significant correlation (P < 0.001) was observed between t-TGA concentrations and EMA. t-TGA showed a sensitivity of 87% and 95%, a specificity of 97% and 100% for adults and children, respectively.

CONCLUSION

The method is highly sensitive and specific in the diagnosis of CD and is promising as a tool for routine diagnostic use and population screening, especially in children.

IgA antibodies against endomysium and transglutaminase: a comparison of methods

Recently, the endomysial antigen has been identified as the protein cross-linking enzyme known as tissue transglutaminase (tTG). Our objective was to compare a novel enzyme immunoassay (EIA) that detects IgA antibody against tTG to two standard IFA methods utilizing thin tissue sections of rat kidney/rat stomach (KS) and distal primate esophagus (PE) as substrates to detect IgA antibody against endomysium (EMA). Sera from 100 patients suspected of having gluten-sensitive enteropathy (GSE) and 23 sera possessing various antibodies used for EIA cross-reactivity studies were included. Additional tests, performed routinely in our laboratory, were utilized to further assess sera from patients suspected having GSE. These tests include anti-gliadin IgA antibody (AGA) and anti-reticulin IgA antibody (ARA) and are part of the European Society for Pediatric Gastroenterology and Nutrition (ESPGAN) revised criteria for diagnosing GSE. When compared to IFA using KS, the tTG EIA had a sensitivity of 87.5%, was 97.1% specific, and had an overall agreement of 94.0%. When compared to IFA using PE, the tTG EIA had a sensitivity of 92.6%, was 93.2% specific, and had an overall agreement of 93.0%. When the KS IFA was compared to the PE IFA for EMA, the KS IFA had a sensitivity of 96.3%, was 91.8% specific, and had an overall agreement of 93.0%. The majority of sera that were positive for tTG but were negative by IFA (KS, n = 2/PE, n = 5) possessed IgA antibodies against gliadin and/or reticulin. Five of six sera with negative results by PE IFA were positive by the KS IFA and possessed one or more antibodies to tTG and/or gliadin and/or reticulin. We conclude that the tTG EIA compares well to both KS and PE IFAs when detecting IgA antibody against endomysium. We do not recommend the use of PE to detect EMA primarily because of the inconsistencies (i.e., tissue selection, quality, and preparation) and limited availability of commercially prepared PE tissue.

Role of anti-transglutaminase (anti-tTG), anti-gliadin, and anti-endomysium serum antibodies in diagnosing celiac disease: a comparison of four different commercial kits for anti-tTG determination

The aims of this study were: (1) to compare the diagnostic efficacy for celiac disease (CD) diagnosis of serum determination of anti-gliadin (AG) (IgA and IgG) and anti-endomysium (AE) with that of anti-transglutaminase (AtTG); and (2) to compare the accuracy of four different assays to measure AtTG. We studied 72 children: the histological diagnosis of CD was made in 38 cases and excluded in the remaining 34 children. In fasting sera we measured AE, AG-IgA and IgG, and AtTG, the latter with four different commercial kits (Eurospital, Medipan, Inova, Arnika). Moreover AtTG was measured in a group of 58 CD children after a gluten-free diet. AE was positive in all but 1 case of CD patients (sensitivity = 97%); false positive results were found in 1/34 controls (specificity = 97%). When a specificity of 95% was fixed, the sensitivities were 97% for AE, 83% for AG-IgA, and 63% for AG-IgG; the sensitivities of anti-tTG were 90, 84, 84, and 75% when measured with Eurospital, Medipan, Inova, and Arnika kits respectively. The new AtTG seems to be accurate enough to be proposed as a noninvasive diagnostic tool for CD diagnosis; the 4 kits analyzed showed similar diagnostic efficacy.

Radioimmunoassay to detect antitransglutaminase autoantibodies is the most sensitive and specific screening method for celiac disease

OBJECTIVE

The aim of this study was to establish the most sensitive and specific screening method for celiac disease. We tested three methods based on different principles, which all detect autoantibodies against the same antigen (tissue transglutaminase).

METHODS

Sixty-two celiac children at the first biopsy (group 1), 78 celiac children on a gluten-free diet (group 2), 14 celiac children on a gluten-challenge (group 3), and 56 controls with a normal duodenal mucosa (group 4) were studied. The methods used were: 1) radioimmunoprecipitation assay using recombinant tissue transglutaminase (RIA); 2) commercial enzyme immunoassay using guinea pig tissue transglutaminase (ELISA); and 3) indirect immunofluorescence method for detection of antiendomysium antibodies (IF-EMA).

RESULTS

RIA antitransglutaminase autoantibodies were detected in 100% of group 1, 43.6% of group 2, 100% of group 3, and none of the control subjects. ELISA antitransglutaminase autoantibodies were detected in 90.3% of group 1, 9% of group 2, 78.6% of group 3, and in none of the control subjects. IF-EMA were detected in 95.2% of group 1, 11.5% of group 2, 92.3% of group 3, and 1.8% of the controls.

CONCLUSIONS

Our results demonstrate a very high sensitivity and specificity of the RIA method to detect antitransglutaminase autoantibodies in comparison to ELISA and IF-EMA assays. We can explain this finding with the use of human recombinant antigen and the increased capacity of the RIA method to detect low titers of autoantibodies. If our data are confirmed by studies on larger series, tissue transglutaminase RIA could be proposed as the best screening method for celiac patients.

Tissue transglutaminase and endomysial antibodies-diagnostic markers of gluten-sensitive enteropathy in dermatitis herpetiformis

The association of Durhing's disease, commonly referred to as dermatitis herpetiformis (DH), with gluten-sensitive enteropathy (GSE) is supported by the presence of villous atrophy and endomysial antibodies (EMA). EMA are found to be a marker of GSE both in celiac disease (CD) and in DH. Since tissue transglutaminase (tTG) is believed to be the major autoantigen in GSE, the aim of our study was to determine the specificity and sensitivity of anti-tTG antibody ELISA compared to the EMA indirect immunofluorescence test. We studied 44 cases of DH, confirmed by the presence of IgA immune deposits in the dermal papillae, and 58 cases of CD conforming to the International Criteria of Diagnosing CD. The control group comprised 161 sera from patients with vesiculobullous disorders other than DH and 106 sera from normal healthy blood donors. Anti-tTG antibodies were detected in 36 of 44 DH (79%) and in 32 of 58 CD (55%) patients. EMA were positive in 33 of 44 DH (74%) and in 36 of 58 CD (62%) patients. Both the EMA and the antibodies to tTG were present in the majority of patients with DH and CD when they were on a normal gluten-containing diet and were absent when on a gluten-free diet for an extended period of time. There were, however, small discrepancies in positivity and negativity in tTG antibody-positive and EMA-negative patients and vice versa. There seems to be a correlation between the EMA titers and the anti-tTG antibody levels. This study confirms the high specificity and sensitivity of anti-tTG antibody ELISA for GSE and its strong correlation with EMA both in CD and in DH. The results of anti-tTG antibody and EMA assays were comparable; however, in DH, tTG was somewhat more sensitive than the EMA test. For screening of DH, it is advisable to perform both EMA and anti-tTG antibody tests.

Malabsorption testing: a review

Malabsorption syndromes often present diagnostic dilemmas to even the most experienced clinicians. Several malabsorption screening tests are available, but d-xylose testing is our initial screening method of choice. Recent innovations such as serum assays for antibodies associated with celiac sprue are improving the work-up of patients with suspected malabsorption. In addition, physicians are applying technological advances in imaging to determine the underlying pathologies responsible for the occurrence of malabsorption and maldigestion. Breath testing remains a controversial modality in the work-up of patients with malabsorption. Tubeless tests of pancreatic function are also the subject of debate due to a lack of sensitivity for diagnosing mild to moderate chronic pancreatic insufficiency. This review identifies and provides critical analysis of new developments in the field of malabsorption testing. The authors also provide a clinical algorithm for diagnosing malabsorption.

New diagnostic findings in coeliac disease

Coeliac disease, a life-long gluten-sensitive disorder, characterized by malabsorption, villous atrophy and crypt hyperplasia, is well recognized. However, the disease is evidently underdiagnosed, and the classic forms constitute only the tip of the 'coeliac iceberg'. Patients with coeliac disease can have subtle symptoms, if any. Diagnostic difficulties may further emerge when minor mucosal changes are found. In coeliac screening and case-finding a novel test, the antitissue transglutaminase test, has proven promising with a sensitivity and specificity of over 95 %. Genetic and immunohistological research has taken a great leap forward. Coeliac disease is strongly associated with HLA-DQ2, coded by the DQA1*0501 and DQB1*02 alleles, or the DQ8 (DQA1*03, DQB1*0302 alleles). The disease is rare in patients who do not share these alleles, a circumstance which can be utilized in diagnostics. An increase in small bowel intraepithelial lymphocytes especially gammadelta+ T-cell receptor-bearing cells is typical, albeit not pathognomonic, for coeliac disease. Combining new symptoms, humoral immunity, genetics and immunohistological staining can today offer a greater diagnostic scope for coeliac disease, especially in cases where clinical presentation and small bowel biopsy findings remain doubtful.