Anti-food IgG assays: Methods and clinical relevance of results. Position of the biology task force of the French society of allergy

There is an increasing tendency in western countries to attribute to food intolerance various clinical types of gastrointestinal disorders, joint pain or rheumatoid arthritis (RA), migraine and chronic fatigue. Several authors have reported a greater frequency of positive anti-food IgG in patients presenting irritable bowel syndrome (IBS), chronic inflammatory bowel disease (IBD) and RA compared to healthy controls. Over the last decade, screening tests have become routinely available on prescription but are also freely available over the Internet. These assays are used to create diets that avoid IgG-positive foods in the hope of improving symptoms thought to be related to the consumption of these foods associated with IgG-mediated intolerance reactions. The purpose of this study is to review the mechanisms involved in food intolerance and the physiological and pathological role of IgG immune response. Commercially available assays for food IgG are reviewed. Studies based on anti-food IgG determination applied to various diseases are reviewed and discussed. Considerable controversy surrounds the clinical relevance of anti-food IgG assays because of their poor positive predictive value. The recommendations made on the basis of these assays are likely to jeopardize the health of patients by delaying correct diagnosis or encouraging them to follow a mostly useless and occasionally harmful diet. The frequently high direct and indirect costs of assays and avoidance diets may be avoided in favor of other diagnostic strategies. Finally, in the current state of medical knowledge, anti-food IgG tests should not be performed routinely to establish a food intolerance diagnosis or to devise an avoidance diet. They should be used solely for research purposes. (C) 2018 Elsevier Masson SAS. All rights reserved.