Testing for Anti-Human Transglutaminase Antibodies in Saliva Is Not Useful for Diagnosis of Celiac Disease

Laboratory tests commonly used in complementary and alternative medicine: a review of the evidence

It is increasingly easy for the general public to access a wide range of laboratory tests. Tests can be ordered online with little or no input from a health professional. The complementary and alternative medicine (CAM) community promote and sell a wide range of tests, many of which are of dubious clinical significance. Many have little or no clinical utility and have been widely discredited, whilst others are established tests that are used for unvalidated purposes. They range from the highly complex, employing state of the art technology, e.g. heavy metal analysis using inductively coupled plasma-mass spectrometry, to the rudimentary, e.g. live blood cell analysis. Results of 'CAM tests' are often accompanied by extensive clinical interpretations which may recommend, or be used to justify, unnecessary or harmful treatments. There are now a small number of laboratories across the globe that specialize in CAM testing. Some CAM laboratories operate completely outside of any accreditation programme whilst others are fully accredited to the standard of established clinical laboratories. In this review, we explore CAM testing in the United States, the United Kingdom and Australia with a focus on the common tests on offer, how they are reported, the evidence base for their clinical application and the regulations governing their use. We will also review proposed changed to in-vitro diagnostic device regulations and how these might impact on CAM testing.

Gluten-related disorders: certainties, questions and doubts

In the last decade, the ingestion of gluten, a heterogeneous complex of proteins present in wheat, rice, barley and probably in oats, has been associated with clinical disorders, such as celiac disease, wheat allergy and recently to non-celiac gluten sensitivity or wheat intolerance syndrome. Gluten-related disorders, which are becoming epidemiologically relevant with an estimated global prevalence of about 5%, require the exclusion of gluten from the diet. For the past 5 years, an important shift in the availability of gluten-free products, together with increased consumption in the general population, has been recorded and is estimated to be about 12-25%. Many people follow a self-prescribed gluten-free diet, despite the fact that the majority have not first been previously excluded, or confirmed, as having gluten disorders. They rely on claims that a gluten-free diet improves general health. In this review, we provide an overview of the clinical disorders related to gluten or wheat ingestion, pointing out the current certainties, open questions, possible answers and several doubts in the management of these conditions. KEY MESSAGE Incidence of gluten-related disorders is increased in the last decade and self-diagnosis is frequent with inappropriate starting of a gluten-free diet. Gluten and wheat are considered as the most important triggers to coeliac disease, wheat allergy and non-celiac gluten sensitivity. Pediatricians, allergologist and gastroenterologist are involved in the management of these conditions and appropriate diagnostic protocols are required.

Salivary changes in oral mucosal diseases

Saliva is a unique biological fluid that can be easily collected and analyzed with low cost and low morbidity. Therefore, there is a growing attention for using salivary biomarkers in the diagnosis and monitoring of disease progress and response to treatment. Salivary changes have been described in relation to oral mucosal diseases. This article discusses the causes and consequences of salivary hypofunction and presents a review of the literature related to changes in salivary parameters in various oral mucosal diseases and in systemic diseases with possible oral mucosal involvement.

Extension of the celiac intestinal antibody (CIA) pattern through eight antibody assessments in fecal supernatants from patients with celiac disease

BACKGROUND

Detection of anti-transglutaminase, anti-endomysium and anti-gliadin antibodies is commonly used to screen celiac disease patients. Besides that in serum, these antibodies are detectable in culture supernatants of oral, duodenal and colonic biopsy samples, saliva, gut lavage fluid samples, and fecal supernatants. Our aim was to extend the intestinal antibody pattern in fecal supernatants from patients with celiac disease.

METHODS

The fecal supernatants obtained from 25 celiac disease patients and 12 healthy volunteers were used to determine IgA and IgG1 anti-endomysium by immunofluorescence analysis, IgA and IgG anti-transglutaminase, IgA and IgG anti-deamidated gliadin peptides, IgA/IgG anti-transglutaminase/deamidated gliadin peptides and IgA anti-actin by enzyme-linked immunosorbent assay.

RESULTS

IgA anti-endomysium were found in 11 of 25 (44.0%) celiac disease patients and in none of healthy volunteers (p=0.0066). The levels of IgA anti-transglutaminase, IgA anti-deamidated gliadin peptides, IgA/IgG anti-transglutaminase/deamidated gliadin peptides and IgA anti-actin determined in celiac disease patients were significantly higher (p=0.0005, p=0.0018, p=0.0061 and p=0.0477, respectively) than those measured in healthy volunteers. The ROC curve analysis showed a diagnostic significance in IgA anti-transglutaminase (AUC=0.862, p<0.0001), IgA anti-deamidated gliadin peptides (AUC=0.822, p<0.0001) and IgA/IgG anti-transglutaminase/deamidated gliadin peptides (AUC=0.783, p=0.0003) fecal tests.

CONCLUSIONS

Our data extend the intestinal antibody pattern detectable in fecal supernatants, thus increasing the knowledge in the humoral immunity of celiac disease. Further studies are needed to better evaluate the role of fecal antibody tests in identifying celiac disease patients.

Identification of human salivary transglutaminases

Transglutaminases (TGs) expression and enzymatic activities in human saliva were investigated. Specific antibodies showed the co-existence of TG1, TG2, TG3 and TG4. TG2 and TG3 were found in native and multiple proteolytic forms. Our data indicate that TG1 and TG2 isoenzymes are highly active with the major activity attributed to TG1. These findings pave the way for future studies on the physiological role of TG in the oral cavity and the potential impact of their deregulation in TG-associated oral diseases.

Orally based diagnosis of celiac disease: current perspectives

Celiac disease (CD) is a lifelong immune-mediated disorder caused by the ingestion of wheat gluten in genetically susceptible persons. Most cases of CD are atypical and remain undiagnosed, which exposes the individuals to the risk of life-threatening complications. Serologic endomysial and tissue transglutaminase antibody tests are used to screen at-risk individuals, although a firm diagnosis requires demonstration of characteristic histopathologic findings in the small-intestinal mucosa. A gluten challenge, with a repeat biopsy to demonstrate recurrence of histopathologic changes in the intestinal mucosa after the re-introduction of gluten, is considered for those persons in whom diagnosis remains in doubt. In this paper, we review studies that evaluated: (1) the possibility of using oral mucosa for the initial diagnosis of CD or for local gluten challenge; and (2) the possibility of using salivary CD-associated antibodies as screening tests. Our review shows that orally based diagnosis of CD is attractive and promising, although additional evaluations with standardized collection and analysis methods are needed. There is some evidence of a dissociation between systemic and oral mucosal immune responses in CD. The hypothesis that gluten could stimulate naive lymphocytes directly in the oral cavity would have important implications for the understanding, diagnosis, and management of CD.

Radioimmunological detection of anti-transglutaminase autoantibodies in human saliva: a useful test to monitor coeliac disease follow-up

BACKGROUND

Serum radioimmunoassay (RIA) tissue transglutaminase autoantibodies (tTG-Abs) proved to be a sensitive test also during coeliac disease (CD) follow-up. We demonstrated that RIA tTG-Abs could be detected in human saliva.

AIM

To evaluate salivary RIA tTG-Abs in coeliac children on gluten-free diet (GFD).

METHODS

Saliva and serum samples from 109 coeliac children were evaluated at diagnosis (group 1: 71 females, median age 9.4 years) and 58 of them on GFD: 36 after 3-6 months (group 2a), 34 at 9 months or more (group 2b). Two gender- and age-matched control groups: 89 gastroenterological patients (group 3) and 49 healthy subjects (group 4) participated in the study. Saliva and serum tTG-Abs were detected by RIA and compared with serum tTG-Abs ELISA and IgA anti-endomysium antibodies (EMA).

RESULTS

Salivary RIA tTG-Abs were found in 94.5%, 66.7% and 50.0% of groups 1, 2a and 2b CD patients and in 98.2%, 72.2% and 50.0% of corresponding serum samples, respectively. tTG-Abs decreased with GFD progression and a correlation was found between saliva and serum titres (r = 0.75, P = 0.0001). During the CD follow-up, salivary and serum RIA sensitivities were comparable, and higher with respect to EMA and ELISA.

CONCLUSIONS

This study demonstrates that it is possible to detect salivary tTG-Abs with high sensitivity not only at CD diagnosis, but also during GFD.

Salivary dysfunction associated with systemic diseases: systematic review and clinical management recommendations

OBJECTIVES

The objective of this study was to identify systemic diseases associated with hyposalivation and xerostomia and develop evidence-based management recommendations for hyposalivation/xerostomia.

STUDY DESIGN

Literature searches covered the English language medical literature from 1966 to 2005. An evidence-based review process was applied to management studies published from 2002 to 2005.

RESULTS

Several systemic diseases were identified. From studies published 2002 to 2005, 15 were identified as high-quality studies and were used to support management recommendations: pilocarpine and cevimeline are recommended for treating hyposalivation and xerostomia in primary and secondary Sjögren's syndrome (SS). IFN-alpha lozenges may enhance saliva flow in primary SS patients. Anti-TNF-alpha agents, such as infliximab or etanercept, are not recommended to treat hyposalivation in SS. Dehydroepiandrosterone is not recommended to relieve hyposalivation or xerostomia in primary SS. There was not enough evidence to support any recommendations for the use of local stimulants, lubricants, and protectants for hyposalivation/xerostomia. However, professional judgment and patient preferences may support the use of a specific product for an individual patient.

CONCLUSIONS

These evidence-based management recommendations should guide the clinician's management decisions for patients with salivary dysfunction related to systemic disease. Future treatment strategies may include new formulations of existing drugs, e.g., local application of pilocarpine. Recent discoveries on gene expression and a better understanding of the etiopathogenesis of SS may open new treatment options in the future.

Diagnosis of coeliac disease

The diagnosis of coeliac disease depends on the finding of characteristic, though not specific changes, of intraepithelial lymphocytosis, crypt hyperplasia and various degrees of villous height reduction identified in duodenal biopsies of individuals ingesting a gluten containing diet, together with symptomatic and histologic improvement on gluten withdrawal. Serologic testing has become the main mode of determining who will undergo biopsy. The IgA endomysial antibody and IgA tissue transglutaminase antibody have approximately 90% sensitivity and specificity, though there are reports of lower sensitivity and specificity in the clinical practice setting. This is due to lower titers of these antibodies in the presence of lesser degrees of mucosal damage. The widespread availability of serologic tests for coeliac disease allows the diagnosis to be considered by any physician. Gastroenterologists will be required to interpret the results of serologic tests and perform duodenal biopsies when indicated. Pathologists likewise need to be better acquainted with the more subtle changes of cell mediated immunity within the mucosa that are suggestive of underlying gluten sensitivity.

Practical considerations for the identification and follow-up of children with celiac disease

Celiac disease is an immune-mediated enteropathy affecting 0.5% to 1% of children and is induced by dietary gluten in susceptible individuals carrying the human leukocyte antigen DQ2 or DQ8 heterodimer. If serological screening is positive or if a patient displays suggestive symptoms, an endoscopic biopsy of the distal duodenum is required to confirm the diagnosis. Symptoms of celiac disease are often mild or absent. Overt malabsorption occurs in only 2% to 10% of children. Individuals with a higher risk of developing celiac disease, including first-degree relatives of affected patients and children with type I diabetes, Turner syndrome, Williams syndrome or Down syndrome, should be offered screening for celiac disease along with a discussion of the implications. If serological testing is negative, a high index of suspicion should remain if malabsorption, iron deficiency or osteopenia is present. Also, immunoglobulin A deficiency should be excluded. At-risk individuals should undergo serial serological screening. Lifelong adherence to a gluten-free diet is the only treatment. If left untreated, symptomatic children with celiac disease carry an increased risk of developing osteoporosis and have a greater lifetime risk of cancer. The long-term outcome of undiagnosed or untreated asymptomatic individuals is less clear.