Food Intolerance - Diagnosis

Diagnosis

Diagnosis of food intolerance can include hydrogen breath testing for lactose intolerance and fructose malabsorption, professionally supervised elimination diets, and ELISA testing for IgG-mediated immune responses to specific foods. It is important to be able to distinguish between food allergy, food intolerance, and autoimmune disease in the management of these disorders. Non-IgE-mediated intolerance is more chronic, less acute, less obvious in its clinical presentation, and often more difficult to diagnose than allergy, as skin tests and standard immunological studies are not helpful. Elimination diets must remove all poorly tolerated foods, or all foods containing offending compounds. Clinical investigation is generally undertaken only for more serious cases, as for minor complaints which do not significantly limit the person's lifestyle the cure may be more inconvenient than the problem.

The Hemocode Food Intolerance System and Rocky Mountain Analytical Food Allergy Test are unvalidated yet heavily marketed examples of ELISA testing of IgG4 to foods. IgG4 against foods indicates that the person has been repeatedly exposed to food proteins recognized as foreign by the immune system. However, its presence should not be considered a factor which induces intolerance. Food-specific IgG4 does not indicate food allergy or intolerance, but rather a normal physiological response of the immune system after exposure to food components. Although elimination of foods based on IgG-4 testing in IBS patients resulted in an improvement in symptoms, the positive effects of food elimination were more likely due to wheat and milk elimination than IgG-4 test-determined factors. The IgG-4 test specificity is questionable as healthy individuals with no symptoms of food intolerance also test positive for IgG-4 to several foods.

Diagnosis is made using medical history and cutaneous and serological tests to exclude other causes, but to obtain final confirmation a Double Blind Controlled Food Challenge must be performed. Treatment can involve long-term avoidance, or if possible re-establishing a level of tolerance.

The antigen leukocyte cellular antibody test (ALCAT) has been commercially promoted as an alternative, but has not been reliably shown to be of clinical value.