False positive reactions for IgA and IgG anti-tissue transglutaminase antibodies in liver cirrhosis are common and method-dependent
Introduction
Celiac disease (CD) is an immunomediated disorder characterised by multiform clinical expressions and the presence of circulating antibodies [1]. Anti-endomysial autoantibodies (EMA) appear at the early stages of the disease, and the EMA test is considered an excellent, non-invasive diagnostic test due to its high sensitivity and specificity [1], [2]. However, this test, based on the indirect immunofluorescence method using primate esophagus as substrate, is not easily applied for large-scale screening. Since Dieterich et al. [3] identified tissue transglutaminase (tTG) as the main autoantigen responsible for EMA positivity in CD patients, it has been possible to prepare immunoenzymatic assays (ELISA) to test for anti-tTG autoantibodies. The first ELISA tests, using guinea pig liver (gp-tTG) as tTG antigen source, demonstrated good diagnostic sensitivity [4], [5], [6], [7], but also low specificity due to the presence of a large proportion of false positive results, especially in patients with chronic liver disease [8], [9]. Later studies demonstrated that these false positives were due to impurities in the antigen source [9], [10], and that the use of the ELISA gp-tTG test is consequently not very practicable for screening patients with persistent, otherwise unexplained hypertransaminasemia.
Subsequently, in a trial conducted on a large number of patients with chronic liver disease, Carroccio et al. [9] demonstrated that the use of recombinant human tTG (rh-tTG) considerably improved the specificity of the test. Recently, however, Vecchi et al. [11] found a high rate (31.6%) of positivity for anti-tTG in patients with liver cirrhosis (LC) not associated with CD, although they also used a method with rh-tTG. In order to establish whether the conflicting results of the above studies were attributable to differences in the methods used, we determined the anti-tTG autoantibodies in a large number of LC patients with 11 different commercial methods, all of which used rh-tTG or human native tTG (nh-tTG) as antigen source.
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Patients
54 patients suffering from LC were studied (34 men, mean age 66.7±11.7 years, and 20 women, mean age 68.6±10.2 years), 32 of whom were HCV+ and 10 HBV+, and 12 of whom suffered from alcoholic or cryptogenetic cirrhosis, all treated at the Liver Unit of the Department of Medicine, Pordenone Hospital, Italy. Patients suffering from cirrhosis secondary to autoimmune hepatitis or primary biliary cirrhosis were excluded from the trial. The first step was to conduct the EMA test on all patients;
IgA anti-tTG
None of the healthy controls or those affected by autoimmune diseases tested positive with the various methods used.
All the CD patients tested positive for IgA anti-tTG with 8 out of 11 methods; the remaining three methods failed to detect positivity in only one case (Table 1 and Fig. 1a) with a low antibody content, and Cronbach's alpha test showed a high degree of agreement between the methods (α=0.979).
However, the methods performed differently in the LC patients, with positivity ranging
Discussion
CD often accompanies liver damage, and hypertransaminasemia, sometimes isolated, can be present in 10–54% of patients [12], [13], [14], [15], [16]. Serological screening for CD is therefore mandatory in patients with otherwise unexplained hypertransaminasemia. Although the EMA test has proved to be highly sensitive and specific, identification of tTG as the main, if not the only antigen responsible for EMA positivity [3] means that the ELISA tests for anti-tTG have rapidly become the most
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Celiac Disease
2017, Foodborne Diseases: Third EditionAssociated autoimmune diseases in children and adolescents with type 1 diabetes mellitus (T1DM)
2015, Autoimmunity ReviewsCitation Excerpt :However recent studies have shown that EMA are sensitive even in younger children [299]. On the other hand anti-tTG-IgA antibodies are determined using ELISA technique, which is easier to interpret, albeit with reportedly low positive predictive value, particularly in low-risk populations and false positivity in patients with hepatic disease [256,300]. Another impediment in the serological diagnosis of CD is the fact that EMA and anti-tTG are IgA antibodies and patients with CD have ten times higher prevalence of IgA deficiency compared to the general population [301].
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2015, Advances in Clinical ChemistryCitation Excerpt :Other authors, however, have not confirmed this observation, finding only AGA positivity with negative IgA anti-tTG antibody results in patients with Giardiasis [196]. False-positive results are also possible in patients with IgA monoclonal gammopathy, chronic liver disease, lymphoma, and rheumatologic diseases [142,197–201]. It has already been emphasized that IgA anti-tTG autoantibody levels may reflect the degree of mucosal damage present [186–191], although there are reports of high levels of IgA anti-tTG in patients without CD [202].
IgA antibodies against deamidated gliadin peptides in patients with chronic liver diseases
2012, Clinica Chimica ActaCitation Excerpt :In addition, most studies reported that IgG anti-DGP antibodies had comparable or even better performance of that reported for IgA anti-tTG and IgA anti-DGP antibodies [15–19], although these studies mainly looked at patients with a clinical suspicion of CD and not in asymptomatic cases. However, the predictive value of all the abovementioned CD-related antibodies in the diagnosis of CD in patients with liver diseases does not appear to be as high as in those without liver disease [20–22]. Indeed, in a previous study of our group, we have reported that the prevalence of IgA anti-tTG antibodies was higher in patients with diverse liver disorders compared to healthy controls, but their specificity for CD diagnosis in this group of patients was low, because of their association with the presence of autoimmunity, cirrhosis and cholestasis, irrespective of the cause of liver disease [23].