Are Double-Blind Food Challenges Necessary Before Starting an Elimination Diet?
Abstract:Food allergy is normally treated by eliminating the offending food. Such a measure, however, may cause nutritional and sociopsychological problems, so an allergy must be diagnosed with the utmost certainty. To date the most reliable diagnostic test is the double-blind food challenge (DBFC).
The rationale for using this test is the marked difference in positive results with open and double-blind food challenges. Only about 30% of open challenges that appear positive are confirmed on blind challenge. There is ample evidence, too, that a negative DBFC may in fact indicate tolerance to that food. From the literature it appears that almost all patients who reintroduced a certain food into their diet after a DBFC had given negative findings did not present any adverse reaction to it.
In our caselist of 21 patients with probable reactions to foods but negative DBFC, 19 (90.5%) tolerated the "incriminated" food well when it was reintroduced into their diet even in unlimited amounts. Only two (9.5%) again presented symptoms when they started taking large amounts of the problem food. Therefore, one precaution recommended before reintroducing afood item into a patient's diet after a negative DBFC is to check how it is tolerated at high doses.
A review of the literature confirms the unquestioned utility of the DBFC. Nevertheless, in some situations this test is not indicated. The main one, of course, is in patients with life-threatening symptoms such as anaphylactic shock or glottis edema, in whom any provocation test is contraindicated. Another situation is when the food items eliminated are not normally present in the patient's diet and are not nutritionally indispensable, in which cases the DBFC can be avoided because it is money- and time-consuming.
Document Type: Research Article
Publication date: September 1, 1991
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- Allergy and Asthma Proceedings is a peer reviewed publication dedicated to distributing timely scientific research regarding advancements in the knowledge and practice of allergy, asthma and immunology. Its primary readership consists of allergists and pulmonologists.
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