Anti-transglutaminase antibody assay of the culture medium of intestinal biopsy specimens can improve the accuracy of celiac disease diagnosis

BACKGROUND: We measured anti-transglutaminase (anti-tTG) antibody in the culture medium of intestinal biopsy specimens from patients with suspected celiac disease (CD) and evaluated the relationship between antibody production and severity of intestinal mucosal damage. METHODS: We performed diagnostic testing for CD on 273 consecutive patients. In addition to routine histologic evaluation of duodenal biopsy specimens, we assayed anti-tTG antibodies in serum and in the culture medium of duodenal biopsy specimens. RESULTS: CD was diagnosed in 191 of the 273 patients. Sensitivity and specificity of the serum anti-endomysium (EmA) and anti-tTG assays were 83% and 85% and 99% and 95%, respectively, and both had 88% diagnostic accuracy. EmA and anti-tTG assayed in the culture medium had 98% sensitivity, 100% specificity, and 98% diagnostic accuracy (vs serum assays; P <0.0001). Twenty-nine CD patient specimens (16%) were negative for serum anti-tTG and EmA; for 24 of these patients, anti-tTG assay of the culture medium was positive. The CD patients whose biopsy specimens were positive for serum antibodies showed the following intestinal histologies: total villous atrophy, 35%; severe villous atrophy, 25%; mild atrophy, 25%; villi with no atrophy but with increased intraepithelial lymphocytes, 15%. None of the CD patients whose specimens were negative for serum antibodies showed total or severe villous atrophy; 77% had mild villous atrophy, and 23% had no villous atrophy but had increased intraepithelial lymphocyte counts. Mild villous atrophy was also seen in specimens from approximately 15% of patients without CD. CONCLUSION: Anti-tTG assay of the culture medium of biopsy specimens can improve the accuracy of CD diagnosis in patients negative for serum antibodies.     

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.     

Low specificity of anti-tissue transglutaminase antibodies in patients with primary biliary cirrhosis

The association between celiac disease (CD) and primary biliary cirrhosis (PBC) is well documented in medical literature; however, a high frequency of false positive results of the anti-transglutaminase (anti-tTG) test has been reported in patients with PBC. To verify if the positive results for anti-tTG autoantibody are false positives due to cross reactivity with mitochondrial antigens, we studied 105 adult patients affected with PBC, positive for anti-mitochondrial M2 antibodies. Anti-tTG IgA antibodies were studied by using six different immunoenzymatic assays that employ the tTG antigen obtained from different sources (human recombinant, placenta, red blood cells, and guinea pig liver). On the whole, 28 out of 105 PBC subjects tested positive for anti-tTG IgA antibodies, but only two were eventually found to be affected by CD; the other 26 were shown to be false positive. The specificity of the various antigenic substrates ranged from 88.5% of the human erythrocytes tTG to 97.1% of the human recombinant tTG. The results of this study showed that a true association between PBC and CD was present in only 2% of the patients and that, in most cases, the false positive results were attributable to the type of substrate utilized in the assay.     

High prevalence of celiac disease in autoimmune hepatitis detected by anti-tissue tranglutaminase autoantibodies

Celiac disease (CD) may be found in association with other autoimmune diseases. We investigated the relation between autoimmune hepatitis (AIH) and CD by assessing the prevalence of IgA and IgG anti-tissue transglutaminase (tTG) antibodies in AIH, and by verifying whether the findings were associated with clinical and histological features of CD. Forty-seven consecutive patients with AIH (type I: n = 39; type II: n = 8) were studied. One hundred patients with chronic hepatitis C, and 120 healthy blood donors were also studied as controls. We analyzed sera for the presence of IgA and IgG anti-tTG antibodies using a specific human recombinant tTG immunoenzymatic assay. Anti-tTG positive patients and controls were further tested for anti-endomysium antibodies (EMA) and HLA typing, and those found positive by either of these tests underwent duodenal biopsy to confirm a possible diagnosis of CD. Three of the 47 AIH patients (6.4%) were positive for IgA anti-tTG and EMA antibodies, and were subsequently confirmed to be affected with CD by small-bowel biopsy findings. No IgG anti-tTG positivity was found in the AIH patients. None of the controls were positive for IgA anti-tTG, and only one with chronic hepatitis C had a low positive reaction for IgG anti-tTG, which resulted as a false positive. The crude prevalence rate of CD in AIH was 63.8 per 1,000 (95% CI, 13.2-186.1), and it was significantly higher than that found in the general population in Italy (4.9 per 1,000; 95% CI, 2.8-7.8). The results of this study showed a high prevalence of CD in patients with AIH. For this reason, early serological screening testing for CD is strongly recommended for all AIH patients.     

False positive reactions for IgA and IgG anti-tissue transglutaminase antibodies in liver cirrhosis are common and method-dependent

BACKGROUND: Conflicting results were obtained in the assay of anti-transglutaminase (anti-tTG) autoantibodies in patients with chronic liver disease. In order to establish whether this was attributable to methodological differences, anti-tTG antibodies were assayed in a large number of patients suffering from liver cirrhosis (LC). METHODS: 54 patients with LC and 29 patients suffering from celiac disease (CD), used as controls, were tested for IgA and IgG anti-tTG with 11 different commercial methods. RESULTS: In the patients with LC, positivity ranged from 0% to 33.3% for IgA anti-tTG and from 0% to 11.1% for anti-tTG of the IgG class. The largest number of false positives was found with methods that used tTG in association with gliadin peptides as antigen substrate. A significant association was found between IgA anti-tTG antibodies and serum immunoglobulin concentration. CONCLUSIONS: The results of the various methods of assaying anti-tTG antibodies in patients with LC are highly variable, and the positives found are generally false positives, partly due to the high immunoglobulin concentration.     

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.     

Use of likelihood ratios improves clinical interpretation of IgA anti-tTG antibody testing for celiac disease

BackgroundWe investigated whether taking into account IgA anti-tissue transglutaminase antibody concentration (IgA anti-tTG) and total IgA concentration could improve clinical interpretation of serologic testing for celiac disease (CD).MethodsWe retrospectively identified 43 consecutive newly diagnosed CD patients and 545 consecutive disease control patients who had an IgA anti-tTG request during the 42-month study period and for whom intestinal biopsy results were available.ResultsSensitivity and specificity of the IgA anti-tTG assay from Genesis was 95.3% and 92.7%, respectively, with a likelihood ratio (LR) of 12.4. The LR for CD markedly increased with increasing IgA anti-tTG concentration (from 2.0 for results between 7 and 20 U/ml up to 319 for results > 100 U/ml). The LR for CD was also higher in patients with a normal IgA concentration (0.82–4.53 g/L) compared to patients with an increased IgA concentration (15.3 vs. 3.1, respectively). These observations were confirmed with a second IgA anti-tTG assay from BioRad.ConclusionSensitivity of IgA anti-tTG was good. Specificity, however, was reduced when IgA anti-tTG was weak positive or when the IgA concentration was increased. Taking into account IgA anti-tTG concentration and IgA concentration improves clinical interpretation of serologic testing for CD.     

Diagnostic performance of IgG anti-deamidated gliadin peptide antibody assays is comparable to IgA anti-tTG in celiac disease

BackgroundDetection of IgG antibodies against deamidated gliadin peptides (DGP) is more sensitive and more specific for celiac disease than detection of IgG antibodies against native gliadin. Our aim was to evaluate the technical performance and diagnostic accuracy of four commercial IgG anti-DGP assays.MethodsCommercial IgG anti-DGP assays from Euroimmun, Inova, Phadia and The Binding Site were evaluated and their diagnostic accuracy (sensitivity and specificity) compared to other serologic assays for celiac disease (3 IgA and 2 IgG anti-tTG assays, 1 IgA and 1 IgG anti-gliadin assay, 1 IgA anti-DGP assay). The study population consisted of 86 consecutive CD patients and 741 disease controls.ResultsThe technical performance (linearity, interference and imprecision) of the IgG anti-DGP assays was acceptable. The sensitivity of the IgG anti-DGP assays varied between 76.7% and 86.0% at the cut-off recommended by the manufacturer and between 74.4% and 86.0% at the cut-off that corresponded to a specificity of 98%. The specificity varied between 97.3% and 99.3%. The diagnostic accuracy of the IgG anti-DGP assays was comparable to the diagnostic accuracy of the IgA anti-tTG assays. The sensitivity of the IgG anti-DGP assays was significantly better than sensitivity of the IgG anti-tTG assays (p < 0.05) and the specificity was significantly better than the IgA and IgG anti-gliadin assays (p < 0.05).ConclusionsThe overall performance of the four IgG anti-DGP assays was acceptable and the diagnostic accuracy comparable to the three IgA anti-tTG assays.     

Diagnostic efficacy of the ELISA test for the detection of deamidated anti‐gliadin peptide antibodies in the diagnosis and monitoring of celiac disease

Background and Aim: We evaluated the diagnostic performance of an ELISA test for anti‐gliadin IgA and IgG antibodies, which uses synthetic deamidated gliadin peptides (anti‐gliadin antibodies, AGAs) as coating; the results were compared with a test that uses extracted gliadin (AGAe). Methods: The study was conducted on the sera of 144 patients suffering from celiac disease (CD), including 20 patients with IgA deficiency and 9 who were following a gluten‐free diet (GFD), and 129 controls. Results: In the 115 CD patients (without IgA deficiency), the sensitivity of AGAe IgA and IgG was 32.2 and 60.9%, whereas that of AGAs IgA and IgG was 59.1 and 72.2%. The specificity for AGAe IgA and IgG, and AGAs IgA and IgG was 93.8 and 89.9%, and 96.9% and 99.2%, respectively. Of the 20 patients with CD and IgA deficiency, 7 tested positive for AGAe IgG and 14 for AGAs IgG. The test using deamidated gliadin peptides performed better in terms of sensitivity and specificity than the AGA tests with extracted antigen. Conclusions: The very high specificity of the AGAs IgG test (99.2%) also suggests that patients who test positive with this assay require a thorough followup, even if the anti‐tissue transglutaminase antibodies (anti‐tTG) and anti‐endomysial autoantibodies (EMA) assays are negative. J. Clin. Lab. Anal. 23:165–171, 2009. © 2009 Wiley‐Liss, Inc.     

Serum IgA tissue transglutaminase antibodies in coeliac disease and other gastrointestinal diseases

We investigated the presence of IgA anti-tissue transglutaminase (tTG) antibodies in untreated coeliac disease (CD) and other gastrointestinal diseases, and compared IgA tTG concentrations with anti-endomysium (EMA) immunofluorescent findings. The study included 116 untreated CD patients (74 female, 42 male, age range 15-78 years, median 47 years), 82 treated CD patients, 65 patients with normal duodenal histology, 260 disease control samples and 29 healthy volunteers. IgA anti-tTG, EMA, and anti-gliadin (AGA) antibodies were measured. Serum total IgA was measured in the CD patients. Two IgA-deficient untreated CD patients were excluded. IgA EMA and IgA AGA were positive in 99 (87%) and 69 (61%), respectively, of the 114 untreated CD patients. Elevated IgA anti-tTG were found in 92/114 (81%) untreated coeliacs, 1/82 (1%) treated coeliacs, 2/65 (3%) non-coeliacs, 10/260 (4%) disease controls and 2/29 (7%) volunteers. Four of the untreated CD patients, with a normal serum total IgA concentration, were negative for all the serological tests. IgA anti-tTG concentrations were significantly higher in untreated coeliacs (median 10200 units/ml) than in other groups (Mann-Whitney, p<0.00001) and compared well with IgA EMA titres (r(2)=0.54; p<0.0001).     

Celiac disease: antibody recognition against native and selectively deamidated gliadin peptides.

BACKGROUND: Selective deamidation of glutamine residues by tissue transglutaminase (tTG) turns gliadin peptides into stronger activators of T cells from celiac disease (CD) patients. We examined the possibility that these modified peptides could be more specific epitopes for circulating antibodies than are native peptides. METHODS: Two native synthetic peptides and their respective modified sequences were used as antigens for ELISA assays: peptide-1, with residues 56-75 of alpha-type gliadin; and peptide-2, with residues 134-153 of gamma-type gliadin. We examined 40 CD patients [31 not being treated with a gluten-free diet (GFD) and 9 being treated with a GFD] and 30 non-CD patients. RESULTS: An enhanced response against deamidated peptides was observed in 4 (IgA) and 22 (IgG) of 31 untreated CD patients for peptide-1 and in 25 (IgA) and 29 (IgG) patients for peptide-2. Higher anti-gliadin antibody and anti-tTG IgA concentrations correlated with increased IgA reactivity to modified peptides. Among the nine treated CD patients, eight also displayed an improved IgG signal for the deamidated sequence. Deamidation of peptides did not increase the reactivity of non-CD sera. CONCLUSIONS: Selective deamidation specifically increases circulating antibody recognition of gliadin peptides in CD patients. This suggests that deamidated gliadin peptides are more specific CD B-cell epitopes than native peptides; this finding may be relevant for designing improved diagnostic tests.     

Testing for IgG class antibodies in celiac disease patients with selective IgA deficiency. A comparison of the diagnostic accuracy of 9 IgG anti-tissue transglutaminase, 1 IgG anti-gliadin and 1 IgG anti-deaminated gliadin peptide antibody assays

BACKGROUND: To evaluate the diagnostic characteristics of commercially available IgG anti-tTG assays in selective IgA deficiency (SIgAD), we tested different IgG anti-tTG methods and compared the results with those obtained from two other tests: one for IgG anti-gliadin (AGA) and one for IgG to deaminated gliadin peptides (DGP). METHODS: 20 CD patients with SIgAD and 113 controls (9 patients with SIgAD without CD; 54 patients with chronic liver disease; 50 healthy subjects) were tested with 9 IgG anti-tTG assays (2 of which are enriched with gliadin peptides), one IgG AGA assay and one IgG anti-DGP assay. RESULTS: Using optimal cutoffs as determined by ROC curves, the sensitivity of IgG anti-tTG methods ranged from 75% (1 kit) to 95% (7 kits) and the specificity from 94% (1 kit) to 100% (5 kits). Sensitivity and specificity were 40% and 87% for IgG AGA, and 80% and 98% for IgG anti-DGP, respectively. CONCLUSIONS: All IgG anti-tTG methods evaluated are reliable serologic assays for the diagnosis of CD in patients with SIgAD and perform better than the gliadin-based assays used in this study. The tests containing both tTG and gliadinic peptides are burdened by a lower specificity than the anti-tTG assays.     

Anti-tissue transglutaminase antibodies in inflammatory bowel disease: new evidence.

Anti-tissue transglutaminase, previously held to be identical to anti-endomysial antibodies in celiac sprue, has been reported in inflammatory bowel disease patients. To investigate these data further, we evaluated serum and intestinal anti-tissue transglutaminase in inflammatory bowel disease patients, with respect to the Crohn's disease activity index and the integrated disease activity index. Study population comprised: 49 patients with Crohn's disease and 29 patients with ulcerative colitis; 45 patients with celiac sprue and 85 autoimmune patients as disease controls; and 58 volunteers as healthy controls. Immunoglobulin A (IgA) anti-recombinant human tissue transglutaminase and anti-endomysial antibody detection in sera and fecal supernatants were performed. Adsorption of positive sera with recombinant human tissue transglutaminase were also performed. Marked increased anti-tissue transglutaminase concentrations were found in celiac sprue, while low-positive values were also found in Crohn's disease and ulcerative colitis. Anti-endomysial antibodies were detectable only in celiac sprue. Antigen adsorption resulted in a significant reduction of the anti-tissue transglutaminase either in celiac sprue or inflammatory bowel disease sera. A significant correlation between anti-tissue transglutaminase and Crohn's disease activity index or integrated disease activity index scores was found. Anti-tissue transglutaminase was also detectable in fecal supernatants from inflammatory bowel disease patients. Data highlight that both circulating and intestinal anti-tissue transglutaminases are detectable in inflammatory bowel disease, and that they are related to disease activity. These features underline that, in addition to anti-tissue transglutaminase, an anti-endomysial antibody test is necessary in the diagnostic work-up of celiac sprue, especially in patients with known inflammatory bowel disease.     

Simultaneous detection of IgA and IgG antibodies against tissue transglutaminase: The preferred pre-biopsy test in childhood celiac disease

Objectives IgA antibodies against tissue transglutaminase (anti-TG2) is a reliable marker of celiac disease (CD). However, IgA-deficient patients are not identified and young children may lack IgA anti-TG2. Combined detection of IgA and IgG (IgA/IgG) against deamidated gliadin peptides (DGP) has shown a high diagnostic performance for untreated CD. Here we examined the utility of IgA/IgG anti-TG2, IgA/IgG anti-DGP and IgA/IgG against a mix of TG2 and DGP (anti-TG2/DGP) in finding CD among children. Methods Serum antibodies against TG2, DGP, and TG2/DGP were determined with ELISA in 242 children referred to a paediatric gastroenterologist. Fifty had untreated CD verified by an intestinal biopsy and 192/242 children had other diseases than CD. Results Forty-eight untreated CD children had increased IgA/IgG anti-TG2, 47/50 had increased IgA/IgG anti-DGP and 46/50 had increased IgA/IgG anti-TG2/DGP. One control subject had increased IgA/IgG anti-TG2 and IgA/IgG anti-TG2/DGP, whereas 7/192 control subjects had increased IgA/IgG anti-DGP. The IgA/IgG anti-TG2 assay had the best performance with a sensitivity of 96%, a specificity of 99.5% and the area under the ROC-curve was 0.996 (95% CI 0.992–1, p?Conclusions Detection of one antibody is not sufficient when screening for untreated CD among children due to cases of IgA deficiency. The inclusion of DGP antigens in the IgA/IgG combination assays seems to affect the sensitivity and specificity negatively, whereas detection of IgA/IgG anti-TG2 has the potential of finding most untreated CD patients, including those with IgA deficiency.     

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.     

A beta-turn rich oats peptide as an antigen in an ELISA method for the screening of coeliac disease in a paediatric population

BACKGROUND: ELISA methods for the measurement of IgA antigliadin antibodies (AGA), both home-made and commercial systems, routinely employ wheat gliadin fractions as coating antigens. We investigate the sensitivity and specificity for CD diagnosis of a new ELISA method using a highly immunoreactive beta-turn rich gamma3-avenin peptide as an alternative coating antigen. METHODS: The assay was standardized with antihuman IgA peroxidase-conjugated as the second antibody. Alternatively, an ELISA based on the use of protein A-peroxidase was assayed to measure both IgG plus IgA antibodies. Sixty-three sera from healthy controls were analyzed to establish the system's cut-off point. Sera from 103 coeliac and from 65 noncoeliac children were tested; for diagnosis purposes, a small intestinal biopsy had been performed in all of them. RESULTS: For the IgA class antibodies assay a high sensitivity and specificity of 90.3% and 98.5%, respectively, was obtained, comparable to those achieved for IgA antiendomysium antibodies (EmA) with the same sera. CONCLUSIONS: In view of the high sensitivity and specificity obtained together with water solubility of the peptide and easiness for large-scale reproducible synthesis, the new AGA IgA avenin peptide ELISA represents a significant improvement in CD diagnosis in comparison with conventional established AGA IgA ELISA using crude gliadins as coating antigens.     

Antibodies against synthetic deamidated gliadin peptides as predictors of celiac disease: prospective assessment in an adult population with a high pretest probability of disease

BACKGROUND: Noninvasive serologic tests have shown high diagnostic accuracy for celiac disease (CD) in selected populations. Our aim was to determine prospectively the performance of CD-related serology in individuals undergoing intestinal biopsy because of clinical suspicion of small-bowel disorders. METHODS: We enrolled 141 unselected consecutive adult patients attending a small-bowel disease clinic. Patients underwent endoscopy and biopsy; serum samples were obtained at that time for measurements of anti-tissue transglutaminase (a-tTG), IgA and IgG anti-deamidated gliadin-related peptide (a-DGP), and IgA antiactin antibodies (AAAs). Characterization of patients was based on histological criteria (Marsh type II lesion or greater). RESULTS: The prevalence of CD was 42.5%. Sensitivity, specificity, and positive and negative predictive values were >90% for most assays. Diagnostic accuracy based on ROC curve analysis was similar for all assays [area under the curve (95% CI): 0.996 (0.967-0.998) for a-tTG, 0.995 (0.964-0.998) for IgA a-DGP, 0.989 (0.954-0.999) for IgG a-DGP, 0.996 (0.966-0.998) for blended conjugated of IgA + IgG a-DGP in a single assay, and 0.967 (0.922-0.990) for AAA]. The combinations of 2 tests, IgG a-DGP plus IgA a-tTG or the single blended conjugate detecting IgA + IgG a-DGP plus IgA a-tTG had 100% positive and negative predictive values if concentrations of both tests in either combination were above or below the cutoff. CONCLUSIONS: In a population with high pretest probability, the newly developed a-DGP tests have diagnostic accuracy that is at least equivalent to that of established assays.     

IgA isotyping of antigliadin antibodies. A possible clue for a less invasive diagnosis of coeliac disease

An enzyme-linked immunosorbent assay was used to measure serum antigliadin antibodies (AGA) of IgG and IgA classes. The assay was modified to measure IgA1 and IgA2 subclasses with monoclonal anti-IgA subclass antibodies. Serum IgG- and IgA-AGA levels were elevated in patients with coeliac disease (CD) but an overlap was seen with control sera. IgA-AGA isotyping using monoclonal anti-human IgA1 and IgA2 antibodies increased the sensitivity and specificity of the assay to almost 100%. All patients with active untreated CD and none of the control groups had elevated IgA1-AGA and IgA2-AGA. In order to measure the relative distribution of IgA1-AGA versus IgA2-AGA an IgA1/IgA2 ratio was calculated. In patients with active untreated CD a ratio of 2.8 was found, declining to 2.2 during treatment. A gluten challenge increased the ratio to 3.4. These findings suggest that IgA1-AGA subclass measurements are a useful screening test before small bowel biopsies are performed. This method can also be used to assess the results of a gluten free diet.     

A novel visual immunoassay for coeliac disease screening

BACKGROUND: To date, the most commonly accepted techniques for the screening of coeliac disease are indirect immunofluorescence and enzyme-linked immunosorbent assay (ELISA), which reveal antiendomysium and antigliadin antibodies respectively. We report the use of a simple visual system for coeliac disease screening based on the use of Staphylococcus aureus protein A, which binds to both IgG and IgA, thus avoiding the need for two parallel immunoassays. MATERIALS AND METHODS: Opaque polystyrene microwell strips coated with a wheat gliadin extract were incubated with sera followed by incubation with protein A-colloidal gold conjugate. The resulting colour was compared with that of positive and negative control sera. The procedure took less than an hour. RESULTS: One hundred and forty-five biopsy-proven sera, 94 from active coeliac patients and 51 from non-coeliac patients with diverse gastrointestinal pathologies or diabetes mellitus, were assayed. Ninety of the 94 sera from the active coeliac patients were positive, whereas only 3 of the 51 non-coeliac control subjects were positive. The technique has a sensitivity of 95.7% and a specificity of 94.1%. CONCLUSIONS: The sensitivity and specificity of the visual system are greater than those of most ELISA systems and are similar to those observed with IgA antiendomysium antibodies when tested in the same population. Moreover, it is inexpensive, quick, simple to perform and easy to interpret, i.e. it requires no qualified personnel. It is for these features, together with the outstanding sensitivity and specificity, that we propose this immunoassay as a new test for reliable coeliac disease screening.     

The prevalence of growth hormone deficiency and celiac disease in short children

OBJECTIVES: To assess the occurrence of growth hormone deficiency (GHD) in patients with celiac disease (CD) referred for short stature. DESIGN: A retrospective, multi-center study. A total of 7066 children with short stature were referred to a number of centers for second-line evaluation over a 5-year period. All patients were screened for CD by antiendomysial antibodies (EMA) and antitissue transglutaminase IgA.Those with positive sera underwent intestinal biopsy. The EMA-negative patients and the EMA-positive ones who did not grow after 1 year of gluten-free diet underwent endocrinological investigation. RESULTS: Among the 7066 short children (age 2-14 years) evaluated, 650 (9.2%) had GHD and 44 (0.63%) had CD. An association of both CD and GHD was found in 16 short children (0.23%); these children did not grow after 1 year of gluten-free diet and therefore GH treatment was started. CONCLUSIONS: GH secretion should be evaluated in celiac patients showing no catch-up growth after an appropriate period on a gluten-free diet in spite of reversion to seronegativity for EMA.