Vijay Kumar, M.D., Research Associate Professor at the University of Buffalo and President and Director of IMMCO Diagnostics: There is no simple answer to this question as the susceptibility of the patient to developing celiac disease is dependent upon several factors. One factor is the amount of gluten intake. Another is the genetic makeup of the individual. However, we feel that several weeks of gluten intake, especially in doses of 2 gm gluten/day, should result in positive serology in patients with celiac disease.
Karoly Horvath, M.D., Ph.D., Associate Professor of Pediatrics; Director, Peds GI & Nutrition Laboratory; University of Maryland at Baltimore: The result of serological tests depends on the diet. Generally, three to six months of a gluten-free diet may result in normal antibody levels in a new patient. A strict gluten-free diet for more than three months may result in inconclusive serological tests in patients, who have started a diet without any diagnostic test. In this case a gluten challenge should be introduced for a proper diagnosis.
A 0.3 g/kg body weight/day of single gluten challenge causes immunological changes (cellular immunity) in the intestine (J Pediatr Gastroenterol Nutr 1989; 9:176-180) in patients on a gluten-free diet, however, the serological response is much slower.
Our recommendation is to ingest at least 0.3 g/kg/day of gluten for two months prior to the serological tests. However, if somebody experiences symptoms during the gluten challenge we recommend to perform serological tests earlier.
The protein content of wheat flour is between 7-15% and approximately 90% of the protein content is gluten. That means a slice of bread may have 2-3 g of gluten.