Alternatives to Oral Gluten Challenge

Celiac.com 12/10/2022 - Increased awareness and celiac disease-specific diagnostic tests have aided the diagnosis of celiac disease. For instance, blood antibody testing has become a useful tool for screening suspected cases of celiac disease. These blood tests can be very sensitive in the detection of patients with severe intestinal damage, but invariably are negative in patients with mild lesions(1). Furthermore, some pathologists are not experienced in recognizing and detecting cases in which mild intestinal damage or even partial villous atrophy is present in biopsy samples. Yet, for these tests to be accurate a patient must be on a gluten-containing diet and doctors often put patients on an oral gluten challenge only after the patient has been on a gluten-free diet and/or their blood antibody tests prove negative.

The oral gluten challenge requires a patient to ingest gluten at the direction of a specialist such as a gastroenterologist for testing purposes such as preparation for an endoscopic exam with biopsies of the small intestine, still considered the gold standard of diagnosis. The demands of the oral gluten challenge are time-consuming, can exacerbate or provoke symptoms, and intentionally put celiac patients at risk for further intestinal damage.

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As a patient, I was gluten-challenged because I had already instituted a gluten-free diet (despite negative blood antibody tests), three weeks before my appointment with the gastroenterologist. I suffered intense and severe symptoms that were provoked by the gluten challenges—not to mention the psychological impact posed by the challenges. At the direction of my gastroenterologist, I was instructed to "make complete damage" in a span of several days upon the first of three, short gluten challenges. At one point, I was ingesting gluten up to seven times in one day. After the close of the third gluten challenge, I felt chronically cold; it was difficult to walk without extreme fatigue and weakness; and I found it difficult to eat or drink due to intense, unrelenting stomach spasms. I had already lost ten percent of my weight before the gluten challenges but lost an additional seven percent after the gluten challenges. Furthermore, I began experiencing heart symptoms and suffered constant and severe joint pain in my extremities. The gluten challenges devastated my already compromised health and made my recovery more difficult and fraught with further complications.

It has become clear that there is a need for methods of testing which do not expose patients to the health risks of an oral gluten challenge. Also, tests that offer more sensitive diagnostic value are needed for prompt and early diagnosis. Several research studies have evaluated the diagnostic potential of various methods without the requirement of an oral gluten challenge. Some of these studies examine the possibility of challenging intestinal biopsies with gluten outside the body in culture media (in vitro). Other studies have tested the immune response elicited by sites outside the small intestine.

In vitro gluten challenge

Today, anti-endomysial antibodies (EmAs) and anti-tissue transglutaminase antibodies (tTGs) are being used in the detection of celiac disease because of their sensitivity (detection of true CD-positive patients) and specificity (omission of non-celiac patients)(2). However, the blood antibody screening tests have not proven sensitive enough in the presence of mild intestinal damage or whereby only an increased intestinal lymphocyte (a type of white blood cell) count is present as a sign of the immune activation(1,3). Therefore, the production of EmA in cultured intestinal biopsies challenged with gliadin has been evaluated for its usefulness in celiac disease diagnosis. Carroccio et al found that EmA positivity of cultured biopsies challenged with gliadin for 48 hours correlated with the degree of intestinal damage, the shorter the treatment with a gluten-free diet (i.e., newly diagnosed celiac patients), and higher counts of inflammatory cells (i.e., white blood cells including lymphocytes) in the intestinal biopsies(2). A higher proportion of celiac patients with more severe intestinal lesions (95%) were EmA positive in their gliadin-challenged cultured biopsies as compared to celiac patients with mild intestinal damage (75%) who were EmA positive. However, this test still had higher sensitivity to detect 58% more celiac patients with mild intestinal damage than the blood EmA tests which were positive in only 17% of them. Furthermore, in newly diagnosed celiac patients, 90% of patients were EmA positive in their cultured biopsies before the addition of gliadin and 96% with the addition of gliadin. Finally, those patients who were EmA positive with the biopsy culture challenge with gliadin had significant higher numbers of inflammatory cells than those who were negative.

Sixty-two percent of celiac patients on a gluten-free diet (GFD-treated) for 12 months, were EmA positive in biopsies challenged in culture with gliadin for 24 hours(4). EmA was not observed in any of their pre-challenge biopsies. However, EmA was detected in all of the cultured intestinal biopsy samples, challenged with gliadin after 72 hours. In addition, none of the control (non-celiac) patients had EmA detectable in their biopsies challenged in culture with or without gliadin.

Local Challenge of Nasal Tissue and Oral Lining

Other exciting prospects in the diagnosis of celiac disease are on the horizon which offer easy access to testing. For instance, other sites outside the intestine such as the nasal tissue and the oral lining are being studied for whether they can elicit a gliadin-specific immune response. In a study of GFD-treated celiac patients, gluten provoked a significant but only mild gliadin-specific inflammatory response in the nasal tissue scrapings (not biopsies) of the celiac patients via activation of lymphocyte cells but not in control patients(5). Another study involved the injection of gliadin into the oral lining of ten GFD-treated celiac patients who were negative for EmA(6). After a 24-hour gliadin challenge, oral biopsies were taken and the number of lymphocytes was significantly increased in celiac patients but not in the controls. Further evaluation of these methods, including studies of untreated patients, is needed to confirm their usefulness in the diagnosis of celiac disease.

Rectal Gluten Challenge

The rectum is an easily accessible site for which a gluten challenge can be performed and rectal biopsies taken7. The test does not require any patient preparation or the more invasive procedure of an endoscopic exam with biopsies. Also, no pre-challenge biopsies are required for comparison.

The diagnostic power of the rectal gluten challenge is demonstrated by its ability to recognize gluten sensitive patients whose blood antibody tests are negative at presentation or whose biopsies are inconclusive(7). The four-hour rectal gluten challenge provided both 100 percent specificity and sensitivity in the diagnosis of gluten-sensitive patients in comparison with blood EmA which had only a 70% sensitivity and 98% specificity. In a group of 45 untreated patients, the rectal gluten challenge showed a significant increase in the numbers of lymphocytes responding to gluten whereas the non-celiac group of patients demonstrated a negative response in their lymphocyte populations. Furthermore, celiac patients on a GFD for two or more years still had more rectal lymphocytes than non-celiacs(8). Post rectal gluten challenge results of biopsy samples disclosed a significantly increased inflammatory infiltration of lymphocyte cells in celiacs but not in control patients.

Inherently, the traditional oral gluten challenge is designed to cause intestinal damage to a celiac patient and may exacerbate or provoke symptoms, which may not be acceptable to the patient. The true cost of a diagnosis of celiac disease is the overt and acute as well as silent and chronic damage to the celiac patient caused by the undertaking of an oral gluten challenge. However, the future use of alternative diagnostic tests in practice offers the patient choices outside the risks and complications of oral gluten challenges. Since rectal gluten challenges, as well as the oral or nasal gluten challenges, must be taken internally, more studies must be done to evaluate the safety of using these potential methods of diagnosis. Some of these studies sought to find a more sensitive way to detect early events in the staging of celiac disease. Others also sought to find if the immune system could identify gliadin outside the gastrointestinal tract to make testing more accessible and easier on the patient. Both the sensitivity and specificity of methods such as EmA detection in cultured biopsies challenged with gliadin may one day change the way celiac disease is currently diagnosed, in the presence of more severe intestinal damage or villous atrophy. Instead, these alternative methods to oral gluten challenge have the potential to facilitate early diagnosis of celiac patients with inconclusive biopsies, those with only mild intestinal damage and negative blood antibody tests as well as high-risk patients such as relatives of celiac patients, and patients with associated autoimmune diseases.

References:

1. Tursi A, et al. 2003. The symptomatic and histologic response to a gluten-free diet in patients with borderline enteropathy. J Clin Gastroenterol 36: 13-17.
2. Carroccio A, et al, 2002. Production of anti-endomysial antibodies in cultured duodenal mucosa: Usefulness in coeliac disease diagnosis, Scand J Gastroenterol 37: 32-38.
3. Tursi A, et al. 2003. Prevalence of antitissue tranglutaminase antibodies in different degrees of intestinal damage in celiac disease. J Clin Gastroenterol 36: 219-21.
4. Picarelli A, et al, 2001. Forty-eight hours of biopsy culture improve the sensitivity of the in vitro gliadin challenge in the diagnosis of celiac disease, Clin Chem 47: 1841- 1843.
5. Torre P, et al, 2002. Immune response of the coeliac nasal mucosa to locally-instilled gliadin, Clin Exp Immunol 127: 513-518.
6. Lahteenoja H, et al, 2000b. Local challenge on oral mucosa with an alpha-gliadin related synthetic peptide in patients with celiac disease, Amer Jour Gastroenterol 95: 2880-87.
7. Ensari A, et al, 2001. Diagnosing coeliac disease by rectal gluten challenge: a prospective study based on immunopathology, computerized image analysis and logistic regression analysis, Clin Sci 101: 199-207.
8. Troncone R, et al, 1996. In siblings of celiac children, rectal gluten challenge reveals gluten sensitization