In Vitro Gliadin Challenge Confirms 'Hard-To-Diagnose' Celiac Disease

October 11, 2011

By Megan Brooks

NEW YORK (Reuters Health) Oct 10 - Challenging biopsied duodenal mucosa with gliadin, the toxic fraction of wheat gluten, can help establish a diagnosis of celiac disease when gluten sensitivity is suspected, but can't be confirmed with standard diagnostic tests, Italian researchers say.

In vitro gliadin challenge is particularly helpful when patients started a gluten-free diet before biopsy samples were taken, said senior investigator Dr. Carolina Ciacci, from the University of Salerno, in an email to Reuters Health.

"People often start the gluten-free diet before diagnosis, just to see if they feel better (often doctors give that wrong advice)," she said. Often such patients "need to return (to) a gluten-containing diet, wait for months, sometimes having symptoms, and repeat blood tests and endoscopy to disclose the presence of celiac disease."

The current study shows that "gluten can be put directly on a biopsy; the biopsy of a person with celiac disease develops inflammation markers upon gluten contact. There is no need to eat it."

In the presence of gliadin, a celiac patient's intestinal mucosa undergoes several modifications that can partly be reproduced in vitro, according to a report online September 27 in the American Journal of Gastroenterology.

Dr. Ciacci and colleagues experimented with in vitro gliadin challenges using duodenal biopsy samples from 337 patients (all adults) at a tertiary center for food intolerance and celiac disease. The cohort included 221 patients with celiac disease (positive controls; 166 untreated and 55 on a gluten-free diet) and 57 patients without it (negative controls). There were also 59 "difficult diagnosis" patients, i.e., people with suspected celiac disease in whom the diagnosis couldn't be confirmed, either because they had already eliminated gluten from their diet or because they had non-concordant diagnostic tests.

In each tissue sample, the researchers measured gliadin-induced mucosal expression of seven inflammatory markers: PY99, ICAM-1 (intercellular cell adhesion molecule), HLA-DR, CD3, CD25, CD69, and transglutaminase 2 IgA.

HLA-DR had the highest accuracy for celiac disease in analyses on negative controls and untreated positive controls (i.e., excluding patients on a gluten-free diet). The area under the receiver operating curve was 0.99. The accuracy of the test did not increase when this marker was combined with any of the other markers.

The findings were similar in a subset of 39 patients in the "difficult diagnosis" group who agreed to go off a gluten-free diet after gliadin challenge for reassessment of celiac disease-specific antibodies.

The findings for HLA-DR, the researchers point out, were consistent at incubation times of three hours and 24 hours, on or off a gluten-free diet, and in patients with difficult diagnosis.

How many people fall into this "difficult diagnosis" category? "Many, many, but nobody knows exactly how many," Dr. Ciacci told Reuters Health.

The investigators note in their paper that this test could provide a psychological boost for patients who don't have celiac disease but are afraid to return to a normal gluten-containing diet.

Dr. Ciacci cautioned, however, that to perform in vitro gliadin challenge "you need an endoscopy unit next to a good laboratory equipped for cell culture. We suggest the test be performed only in celiac disease/food intolerance centers."

Dr. Daniel Leffler, director of clinical research at the Celiac Center at Beth Israel Deaconess Medical Center, Boston, told Reuters Health, "improvements in diagnosis of celiac disease in people on a gluten free diet are greatly needed."

"This is a well designed and performed study," added Dr. Leffler, who was not involved in the study. "However, the techniques used, namely HLA-DR expression in cultured duodenal biopsies, is probably too complicated to be done in routine clinical use and will be limited to specialized research centers."

SOURCE: http://bit.ly/nQTpVL

Am J Gastroenterol 2011.

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