Serological markers and celiac disease: a new diagnostic approach?

Diagnosing and Monitoring Celiac Patients with Selective IgA Deficiency: Still an Open Issue

Although, the association between celiac disease (CD) and selective immunoglobulin A deficiency (SIgAD) has been known for more than fifty years, the procedures for diagnosing and monitoring patients with both conditions are still far from definitive. When serological markers were introduced as pre-bioptic investigations, it was immediately clear that searching for specific IgA antibodies without checking total serum IgA could lead to a failure in diagnosing IgA-deficient CD patients, while specific IgG antibodies could be useful as additional tests, because they are frequently found in the serum of affected patients. Nonetheless, until recently the diagnosis of CD in IgA-deficient patients was based on the few, fragmentary and often contradictory data available in literature. The introduction of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) guidelines in 2012 provided the current criteria for diagnosing CD in IgA-deficient patients, although some issues remained open, such as the selection of patients who should undergo specific IgG antibody testing and the choice of the most reliable IgG-based test for both diagnosis and follow-up. A real-life study recently assessed the impact of the 2012 ESPGHAN guidelines in diagnosing and monitoring CD in SIgAD patients, highlighting several pitfalls that can lead to operational uncertainties and difficulties in patient management. In the present report, the evolution of diagnostic tools and criteria for CD in SIgAD patients has been critically assessed, both strengths and open issues have been highlighted, and future perspectives for improving the current diagnostic protocols have been suggested.

Dermatitis herpetiformis: from the genetics to the development of skin lesions

Dermatitis herpetiformis (DH) is a rare autoimmune disease linked to gluten sensitivity with a chronic-relapsing course. It is currently considered to be the specific cutaneous manifestation of celiac disease (CD). Both conditions are mediated by the IgA class of autoantibodies, and the diagnosis of DH is dependent on the detection of granular deposits of IgA in the skin. There is an underlying genetic predisposition to the development of DH, but environmental factors are also important. This paper describes these different factors and discusses the known mechanism that lead to the development of skin lesions.

Outcome of infants with celiac disease

AIMS

Determine the proportion of infants whose celiac disease (CD) was confirmed in childhood and evaluate their prognosis in adulthood.

PATIENTS AND METHODS

The diagnosis of CD was established between 1971 and 1982 in 84 infants based on intestinal biopsy data; a gluten-free diet was prescribed and the cohort followed prospectively.

RESULTS

Thirty-six infants were followed less than 5 years. A second biopsy was performed in 25. Mucosa had healed in 13 and remained atrophic in 12. Three children developed partial villous atrophy between 6 and 12 years of age in spite of the gluten-free diet. Forty-five patients underwent a gluten challenge between 5 and 10 years of age: in 41 histological lesions relapsed, in two mucosa remained normal and clinical and immunological relapse developed in two. Among those 45 patients, 18 were examined after 18 years follow-up: the exclusion diet was resumed in four, overt clinical relapse developed in four and four experienced intermittent gastrointestinal disorders. All biopsies performed during a period of normal diet showed villous atrophy (except in one patient) without correlation with clinical symptoms.

CONCLUSION

The diagnosis of celiac disease in infants was confirmed in nearly all cases in childhood. When they reached adulthood, these patients had few symptoms but their histological lesions persisted. These data are in favor of a lifelong exclusion diet.

Even small amounts of gluten cause relapse in children with celiac disease

BACKGROUND

Previously, a gluten challenge was customary to establish the diagnosis of celiac disease in children. There are no clear recommendations on how to perform this challenge or what markers to rely on for timing the biopsy after the challenge. The authors' aim was to monitor gluten intake, clinical symptoms, and antibody kinetics to evaluate the influence of gluten exposure during the challenge.

METHODS

Twenty-five children under investigation for suspected celiac disease were challenged. One child was excluded because blood samples, food records, or biopsy was lacking. Median age at the postchallenge biopsy was 3.8 (2.7-8.8) years. The families kept daily records of the children's gluten intake and of symptoms that occurred. Blood samples were taken monthly for analysis of antigliadin and endomysium antibodies and total immunoglobulin A (IgA). A third biopsy was performed when clinical symptoms suggested a relapse.

RESULTS

All 24 children showed deterioration of the mucosa or elevated antibodies during gluten challenge. Median duration of the challenge was 13 (5-51) weeks, and mean gluten intake was 1.7 (0.2-4.3) g/d and 0.1 (0.02-0.26) g/kg daily.

CONCLUSIONS

Gluten intake during the challenge varied widely, and the parents were unable to give their children the recommended amount. Despite the small amounts given, all children showed signs of relapse at a clinical, laboratory, or histologic level. Much smaller amounts of gluten than previously suggested seem sufficient to cause relapse during gluten challenge in children.

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.

Antiendomysium antibodies in Brazilian patients with celiac disease and their first-degree relatives

BACKGROUND

Literature data have shown high specificity of antiendomysial antibodies (EmA IgA) in celiac disease. The scarcity of Brazilian reports concerning this subject motivated the present study.

OBJECTIVES

To determine the sensitivity and specificity of antiendomysial IgA antibodies in Brazilian celiac patients at diagnosis and after treatment, to confirm patient adherence to a gluten-free diet and to screen first-degree relatives.

METHODS

An extensive clinical and serological study was performed by investigating the presence of these antibodies in 392 individuals from Southern Brazil. Indirect immunofluorescence using human umbilical cord as substrate was employed and the total levels of IgA were determined by turbidimetry in all groups. The study was conducted on 57 celiac patients (18 at diagnosis, 24 who adhered to a gluten-free diet and 15 with marked or slight transgression of the diet), 115 relatives of celiac patients (39 families), 94 patients with other gastrointestinal diseases, and 126 healthy individuals from the general population.

RESULTS

The results demonstrated 100% positivity for the recently diagnosed patients and for those consuming gluten, in contrast to the patients who complied with the diet (0%). In the control group one individual was positive, but refused to undergo a biopsy. In the group of other gastrointestinal diseases, one positive patient presented ulcerative colitis, Down's syndrome and epilepsy, and the intestinal biopsy was diagnostic for celiac disease. These data showed 99.3% specificity for the test. Eighteen relatives were positive for antiendomysial antibodies IgA (15.65%), and comparison with the healthy population revealed a significant difference. An intestinal biopsy was obtained from seven subjects (one with total villous atrophy and six without alterations in the mucosal architecture, but all with a high number of intra-epithelial lymphocytes).

CONCLUSIONS

The method revealed 100% sensitivity and 99.3% specificity. Because it is not an invasive method it can be used for the screening of atypical and latent forms of celiac disease to avoid serial biopsies and to control adherence to a gluten-free diet with implications in the prevention of malignancy in celiac disease.

Antibodies to gliadin, endomysium, and tissue transglutaminase for the diagnosis of celiac disease

BACKGROUND

Tissue transglutaminase has recently been identified as the main autoantigen recognized by antiendomysial antibodies in celiac disease. Serum immunoglobulin (Ig)A antibodies to tissue transglutaminase (tTG-ab) determined by an enzyme-linked immunosorbent assay (ELISA) technique have been reported to correlate closely with IgA antiendomysial antibodies (EMA). The purpose of this study was to assess the sensitivity, specificity, and predictive value of tTG-ab measured by a commercially available ELISA technique, compared with those of EMA and IgA antigliadin antibodies (AGA) for the diagnosis of celiac disease.

METHODS

Twenty-seven serum samples were obtained from patients with untreated celiac disease, 37 from patients who had had gluten withdrawn from their diets for varying time spans, and 34 from control subjects without celiac disease. All were younger than 14 years. Presence of tTG-ab and AGA was determined by ELISA and of EMA by indirect immunofluorescence.

RESULTS

Twenty-six of 27 serum samples obtained from patients at the time of diagnosis of celiac disease were AGA positive. All 27 (concordance rate 100%) were positive for EMA and tTG-ab. Of the 34 control subjects, 1 was for AGA and 2 for tTG-ab. All 34 were negative for EMA. Sensitivity, specificity, positive predictive value, and negative predictive value within this group were, for tTG-ab: 100%, 94%, 93%, and 100%, respectively; for EMA: all four indexes were 100%; and for AGA: 96%, 97%, 96%, and 97%, respectively. Of the 37 with treated celiac disease, 2 were AGA positive, 9 were EMA positive, and 6 were tTG-ab positive. The concordance rate between EMA and tTG-ab was 100% in the group with untreated celiac disease, 94% in the control subjects, and 76% in the group with treated celiac disease.

CONCLUSIONS

Immunoglobulin A antibodies to tissue transglutaminase are new, highly sensitive, and specific markers of celiac disease. They can be determined easily by an accurate, comparatively cheap technique and thereby may advantageously replace the EMA marker traditionally used.

Application of red cell distribution width to screening for coeliac disease in insulin-dependent diabetes mellitus

Coeliac disease has been reported to occur in 2-5 per cent of insulin-dependent diabetic patients (IDDM). Suitable non-invasive screening tests would allow identification of these patients. The aim of this study was to determine the value of the red cell distribution width (RDW) in detecting unrecognised coeliac disease in insulin-dependent diabetic patients (IDDM). All patients (n = 208) attending the Diabetic out-patient clinics at 2 adjacent centres who had a full blood picture and RDW carried out in the past 18 months were included. IDDM patients with an elevated RDW were identified and their charts were reviewed to determine if they had symptoms or laboratory abnormalities compatible with coeliac disease. They were invited to attend for serological screening. Ninety-five of 208 patients had an elevated RDW of whom 66 had non-insulin dependent diabetes mellitus and 29 had IDDM. Two of the 29 IDDM patients had died in the interim period. Six of the remaining 27 IDDM patients had previously been tested for serological markers associated with coeliac disease, of whom 1 had a positive antigliadin antibody titre (IgA-AGA 199 EU) and normal duodenal biopsy. Eighteen of the remaining 21 patients with IDDM consented to serological testing of whom only 1 had a positive titre of antiendomysial antibody (IgA-EMA) and villous atrophy. Although the RDW is known from previous studies to be a sensitive predictor for coeliac disease, this study has demonstrated its poor specificity in predicting IDDM patients who may have coeliac disease. The RDW is not recommended as a screening test for coeliac disease in patients with IDDM.

Prospective significance of antiendomysium antibody positivity in subsequently verified celiac disease

BACKGROUND

In order to assess their long-term predictability for the diagnosis of celiac disease, antiendomysium antibody results were compared with the outcome of the Interlaken diagnostic process.

METHODS

Prospective gluten challenge was performed in 153 children with previously diagnosed flat small-intestine mucosa. In 90 patients (Group A), endomysium antibodies were initially positive, in seven (Group B) they were negative, and 56 patients (Group C) had no initial serological results. In IgA-deficient persons, IgG antibodies were also assayed, both by the immunofluorescent method.

RESULTS

Histological relapse rates were 100% (90/90), 14.3% (1/7), and 76.8% (43/56), p < 0.001, in Groups A, B, and C, respectively. Each patient with relapse also exhibited endomysium antibody positivity during the challenge. Patients in whom celiac disease could be finally ruled out remained consistently endomysium-antibody negative. The celiac disease patient in Group B had severe secondary immunoglobulin deficiency at entry, which explained the initial negativity. Diagnosis based on antiendomysium antibody positivity and flat mucosa gave a higher applicability (92.8 vs. 50.3%) and reliability (relapse rate 100 vs. 89.6%) than the 1990 European Society of Paediatric Gastroenterology and Nutrition (ESPGAN) criteria among these patients.

CONCLUSIONS

Endomysium antibody positivity at presentation has been found to be as useful as gluten challenge in the diagnosis of celiac disease, even in patients under the age of 2 years. Challenge is still advisable in patients with a flat small intestinal mucosa when antiendomysium antibody results are negative or have not been done, as among these patients significantly lower relapse rates were found.

Biochemical tests in diseases of the intestinal tract: their contributions to diagnosis, management, and understanding the pathophysiology of specific disease states

Biochemical testing plays a major role in the complete evaluation of patients with suspected or established intestinal disease. We have classified these tests according to the medium in which they are performed: breath tests, including isotopic and nonisotopic tests, fecal tests, urine tests, serum tests, tissue tests, and other tests. The principles of various tests are outlined, and the role of each test in the evaluation of particular gastrointestinal disorders is discussed.

Evaluation of six anti-gliadin antibody assays

Two in-house methods developed in gastroenterological laboratories for the detection and quantitation of IgG and IgA antibodies to gliadin (AGA) were compared with three commercially available ELISAs (gluten IgG/IgA EIA, Kabi Pharmacia, Sweden; alpha-Gliatest, Eurospital, Italy; AGA Orkit, Labodia, Switzerland) and one qualitative rapid assay (Gliastick, Eurospital, Italy). 67 acute, biopsy confirmed coeliac disease cases were compared with 54 biopsy confirmed disease controls. The result of anti-endomysium antibody (AEA) testing was available from all cases. The testing of 121 sera in different test systems permitted comparison of the range of concentration and sensitivity of the quantitative IgG and IgA anti-gliadin tests. Each test uses its own arbitrary calibration. To permit direct comparison of the different test ranges the values of the different positive reference sera were converted into Pharmacia arbitrary units (AU). The AGA and IgG tests ranged from 0 to a maximum of 157-430 AU and the maximum IgA test results from 81 to 855 AU. This illustrates the need for an internationally accepted standard. All three EIA kits met the performance claims of the manufacturers and were easy to use. Most results agreed with the clinical diagnosis when the sera were positive for anti-endomysium antibodies. However, AEA negative specimens showed a considerable incidence of positive AGA in non-coeliacs. The study emphasises the need to test for both AGA and AEA in order to reliably diagnose coeliac disease. The qualitative test showed a high degree of false positive results and could be used to monitor the dietary compliance of coeliac patients.

Celiac disease and hypoparathyroidism: cross-reaction of endomysial antibodies with parathyroid tissue

Celiac disease (CD) is a gluten-sensitive enteropathy characterized by the presence of serum antibodies to endomysial reticulin and gliadin antigens. CD has been associated with various autoimmune endocrine disorders, such as diabetes. We report a rare case of idiopathic hypoparathyroidism with coexistent CD characterized by the presence of serum autoantibodies. Studies were conducted to determine the specificities of these autoantibodies and to localize the antibody binding sites by indirect immunofluorescence and immunoelectron microscopy. Sera from a patient with idiopathic hypoparathyroidism and CD and from two patients with CD alone were tested by indirect immunofluorescence for autoantibodies to parathyroid and endomysial antigens. The specificities of the antibody reactions were determined by testing the sera before and after absorption with monkey stomach tissue. In addition, immunoelectron microscopic studies were performed to determine the localization of the endomysial antigen. Indirect-immunofluorescence studies on the patient's serum were positive with the parathyroid as well as the endomysial substrate. Similar reactions were also observed with the sera of endomysial antibody-positive patients with CD. Absorption of the sera with monkey stomach powder, which is known to have the endomysial antigen, abolished the antibody activities on both the endomysial substrate and the parathyroid tissue. Immunoelectron microscopic studies showed that endomysial antibody activity was associated with antigens localized on the myocyte plasma membrane and in the intercellular spaces. Thus, reactions of the patient's serum with the parathyroid tissue were due to endomysial antibodies and were not parathyroid specific as in patients with idiopathic hypoparathyroidism who did not have coexistent CD. In conclusion, indirect-immunofluorescence tests on parathyroid tissue detect not only tissue-specific antibodies but also cross-reactive antibodies, and this should be taken into consideration when these tests are performed.

Is small bowel biopsy necessary in adults with suspected celiac disease and IgA anti-endomysium antibodies? 100% positive predictive value for celiac disease in adults

The comparative diagnostic value of IgA anti-endomysium and IgA antigliadin antibodies in adults with histologically confirmed celiac disease is reported. Sera from 144 adult patients (without concurrent dermatitis herpetiformis or IgA deficiency) who underwent small bowel biopsy were analyzed for both IgA anti-endomysium and IgA anti-gliadin antibodies. Nineteen patients (13%) had celiac disease. The presence of IgA antiendomysium antibodies had a sensitivity of 74% and a specificity of 100%. The positive and negative predictive values were 100% and 96%, respectively, and the diagnostic accuracy was 97%. In contrast, IgA anti-gliadin antibodies had positive and negative predictive values of 28% and 96%, respectively, with a diagnostic accuracy of 71%. Based on these data, we suggest that small bowel biopsy is not necessary to diagnose celiac disease in symptomatic adults with IgA antiendomysium antibodies. Due to a negative predictive value of 96%, some symptomatic adults lacking anti-endomysium antibodies will not be correctly diagnosed without small bowel biopsy.

Antiendomysium antibodies and coeliac disease: solved and unsolved questions. An Italian multicentre study

A total of 3783 subjects were enrolled to compare IgA and IgG gliadin antibodies (AGA) with IgA endomysium antibodies (EMA) in coeliac disease (CD). Among 688 children with untreated CD EMA were positive in 93.8%, IgA AGA in 84.9% and IgG AGA in 90.2%. AGA, but not EMA, sensitivity decreased with age. EMA were present in 3.8% of control subjects, IgA AGA in 14.9% and IgG AGA in 34.3%. Follow-up of 5 of 39 EMA-positive controls showed flat mucosa. Combined determination of EMA and AGA showed an increased predictive value: if EMA and AGA were both positive, the mucosa was flat in 99.1%, if both were negative, the mucosa was normal in 99.1%. After a gluten-free diet (GFD), IgA-AGA disappeared first. Among 21 patients not on a strict GFD and in 194 coeliac patients after challenge, EMA, but not AGA, were always positive. Among 67 first-degree relatives of coeliacs, the positive predictive value of EMA was 90.6%, IgA AGA 74.3% and IgG AGA 44.6%. In conclusion, EMA screening is an excellent test for the diagnosis and follow-up of CD, and for identification of its silent and latent forms.

Celiac disease: clinical features and pathogenesis

Celiac disease is a fascinating illness, from both a clinical and research perspective. Most clinicians consider a diagnosis of celiac disease when a young patient has classic signs and symptoms of steatorrhea and severe malabsorption. However, the typical gastrointestinal symptoms often are absent. The patient may only have subtle signs of chronic malnutrition or nonspecific gastrointestinal complaints. Celiac disease is not diagnosed commonly in the United States, at least in part because of a low clinical index of suspicion. A diagnosis of celiac disease is confirmed by a small bowel mucosa biopsy. A dramatic clinical response to a gluten-free diet verifies the diagnosis, and provides a cost-effective treatment free of significant side effects. Strict adherence to the prescribed diet usually results in a complete resolution of the symptoms and mucosal histopathologic changes. The serious, long-term complication of intestinal lymphoma also may be prevented. To the clinical investigator, celiac disease is an important model of the HLA-associated immune-mediated illnesses. A specific HLA-DQ heterodimer is found in 95% of patients, representing perhaps the strongest association of any illness with a specific class II HLA molecule. In addition, an important environmental trigger (gluten) has been identified, providing a unique opportunity to study the interaction of gene products and environmental factors in the pathogenesis of an immune-mediated disease.

Evaluation of the gliadin antibody test for diagnosing coeliac disease

The purpose of this study was to evaluate the diagnostic value of gliadin antibodies (GA) in coeliac disease. The test was a diffusion in gel enzyme-linked immunosorbent assay (DIG-ELISA), with combined determination of IgA and IgG. The sensitivity, specificity, and positive and negative predictive value of the test were determined, as used on a well-described, consecutive material of 100 adult patients, admitted for small-intestinal biopsy. For comparison, the positive predictive value of the test, when used on a larger Danish patient material of adults and children, was determined. One hundred and eighteen adults and 55 children with increased or borderline GA were included. For adults the positive predictive value was 71-90%, the negative predictive value 97%, sensitivity 77%, and specificity 95%. For children the positive predictive value was 74%. A graded interpretation, improving the usefulness of the test, is proposed. It is concluded that GA are useful in screening for coeliac disease (CD). It is still necessary to perform at least one small-intestinal biopsy to establish the diagnosis. Highly elevated GA levels strongly indicate CD, whereas a result well below limits makes CD unlikely.

Immunological diagnosis of childhood coeliac disease: comparison between antigliadin, antireticulin and antiendomysial antibodies

The immunological markers proposed to supplement intestinal biopsy for the diagnosis of coeliac disease are antigliadin, antireticulin and antiendomysial antibodies. These antibodies have been studied separately or compared as pairs, but no prospective comparison of all three antibodies in childhood coeliac disease exists. Thirty-four confirmed coeliacs were compared with nine non-coeliacs with pathological small intestines, and 32 children with a normal intestinal histology. Sera were examined for IgG- and IgA-antigliadin antibodies (AGA) by ELISA, and for IgA-antireticulin antibodies (ARA) and IgA endomysial antibodies (EMA) by indirect immunofluorescence. In active coeliac disease, IgA-EMA was the most sensitive (97%), while IgA-AGA the least sensitive antibody (52%). The specificity of IgA-AGA, IgG-AGA, IgA-ARA, IgA-EMA was 95%, 92%, 100% and 98%, respectively. Positive predicted values of ARA and EMA were comparable (97-100%), while EMA had the highest negative predicted value (98%). Compared with IgG-AGA, IgA-EMA titres better reflected variations in dietary gluten, and correlated best with intestinal pathology. Compared with AGA and ARA sensitivity, specificity and predictive values, EMA is the most reliable serological marker for the diagnosis of coeliac disease. It reflects dietary changes in gluten and correlates best with intestinal histopathology. Therefore, it should be considered the best of the three serological tests available for childhood coeliac disease.