One of the difficulties in managing celiac disease is knowing whether or not you are on a truly gluten-free diet. This question comes up if your symptoms do not go away. It also comes up if you had a “silent” presentation and were diagnosed because of early osteoporosis or iron deficiency anemia. In cases like that, you don’t have the gastrointestinal symptoms to let you know if there is gluten hidden in something you are eating.
Doing repeated biopsies to check to see if your small intestine is looking normal is not a good screening test for this, although it is often done. It is too uncomfortable and expensive to be an ideal way answer this question. Blood tests may also not be useful, because the antibody blood tests for celiac disease may take years to normalize even in someone on a gluten-free diet.
Researchers are looking for a test that is easy and inexpensive to do, and will detect gluten that may have been eaten. Research into what parts of gluten cause the reaction in people with celiac disease has yielded a lot of information. What are called a-gliadin 33-mer epitopes (33EPs) seem to be the parts of the gluten that provokes the reactions. This part of the gluten has been used in research to see if it can be removed so that gluten can be safe to eat. There is an antibody test (antigliadin 33-mer G12 antibody) already being used in research to identify the parts of gluten (peptides) that people with celiac disease react to.
Now research is being done to see if these substances could be found in feces. This could be accomplished by using the same antibody tests used to examine food for gluten and to see if it has been made safe.
A recent study was done using normal volunteers without celiac disease as well as patients with celiac disease. The patients without celiac disease were tested after diets with varying amounts of gluten, small and large.
For celiac patients, stool samples were collected before initiating the gluten-free diet, after patients on the gluten-free diet had no symptoms, and after a gluten challenge given to patients in remission.
The first tests were done to check how well the tests would work on parts of gluten after digestion was simulated by using the gastric enzyme pepsin and other digestive enzymes. A variety of tests were performed on these samples and showed that the tests could detect 33EPs after the digestive simulation.
Then, subjects without celiac disease were given a normal diet for a week followed by a 10 day gluten-free period, to see how long it took gluten peptides to leave the intestinal tract. It took two to four days. Healthy volunteers were then given the gluten-free diet for a week, followed by 9 grams of gluten a day for four days, then 40 grams of gluten for four more days.
There was a correlation between the amount of gluten consumed and the amount of 33EPs detected in feces. To check and see if small amounts could be detected, subjects were given very small amounts of gluten, from 50 mg to 1 gram per day. There were detectible 33EPS after as little as 50 mg of gluten.
Participants with celiac disease were then tested. Of 43 patients in remission on gluten-free diets, 42 had undetectable amounts of the gluten peptides. The one patient who tested positive admitted to eating cake during the testing period.
Patients with active celiac disease eating a normal diet with gluten tested positive for the 33EPs.
Patients in remission were given a gluten challenge for 6 days. These were three patients who requested the challenge to confirm their diagnosis. Two of the three developed abdominal symptoms within the first few days and were not studied further. The third patient did not develop symptoms. He had gluten-derived peptides in his stool starting on the third day of the gluten challenge.
While this was one patient, it did confirm that a patient with celiac disease who eats gluten and does not develop symptoms can still have the digested parts of the gluten in measurable amounts in stool.
Given all this information, the researchers believe that this test can detect the products of gluten ingestion in feces after as little as 50 mg of gluten is eaten. The digested products appear between two and four days after gluten ingestion.
The researchers suggest that tests like these could be used to monitor compliance with a gluten-free diet. The digested peptides would be detected whether or not a person believed themselves to be on a gluten-free diet but had contaminated food, or if they were just eating gluten.
Refractory celiac disease is more serious than celiac disease that responds to treatment. These tests could be used to try and exclude people who are in fact not really on a gluten-free diet. Continued gluten in the diet, whether knowingly or not knowingly is usually the reason for continued symptoms.
The authors concluded by suggesting that their testing methods could be used to monitor dietary compliance with a gluten-free diet because they are non-invasive, sensitive, and correlate well with the amount of gluten consumed.
So, at some time in the future, your doctor may wind up asking you for stool samples. They already do this routinely to check for blood, or in patients with other problems, they test for parasites. There are actually lots of stool tests. This may turn out to be one that can help doctors and patients answer questions about whether or not gluten has really been removed from their diet.