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Double-blind placebo-controlled food challenge (DBPCFC) with food items applied in capsules was performed in a prospective study of 17 selected patients and 34 age- and sex-matched healthy controls in the interdisciplinary clinical setting. Protein immunoblotting showed no differences in antigenicity between foods in the capsules and the corresponding fresh foods. All patients reacted to one or more food substances during DBPCFC, with a doubtful reaction to placebo in 2 patients. Agreement between diet history and provocation was seen in 53 of 85 individual food challenges, 36 being positive with both examinations. In 22 (38%) of the 58 positive provocations, the reactions were not expected from the patients' histories. No reaction to food or placebo occurred in the control group. Related to diet history, sensitivity and specificity of provocation were 62 and 63%, respectively, with a positive predictive value of 78%. Allergy, previous gastroenterologic and infectious diseases among first-degree relatives, immunologic abnormalities and elevation of total IgE were significantly more common for the patients than controls. A positive skin prick test correlated well with diet history, but both prick test and food antibodies correlated poorly with DBPCFC. Assessment by the General Health Questionnaire showed a significant difference towards the controls. After 3-4 months of follow-up on an individually based diet, 11 of 15 patients reported general improvement of their condition. DBPCFC may be a valuable diagnostic test in addition to dietary history as a basis for elimination diet on food-intolerant patients. The effect of the elimination diet on the symptoms may also suggest a therapeutic effect or provocation.(ABSTRACT TRUNCATED AT 250 WORDS)