Double-Blind Placebo-Controlled Food Challenges

Accuracy of Food Challenges:

Food challenges are the "gold standard" of food allergy diagnosis. But they are not 100% accurate. It is possible for DBPC food challenges to return false negatives, false positives, and ambiguous results.

False negatives --- that is, no reaction to a food that is actually an allergen --- can occur for several reasons:

  1. Some allergic reactions are exercise-induced or require another circumstance (a psychological, physical, or medical factor) to show up. These circumstances are called augmentation factors and are difficult to test for in a food challenge.
  1. Certain drugs (like antihistamines) the patient may have been taking prior to the test may interfere with the test, causing a false negative.
  2. Patients can, in some cases, develop a short-term oral tolerance induction, or SOTI, to the food they're being tested for. This means that the body may become accustomed to the small amounts of food delivered in the capsules and may not react as the dosage increases. SOTI, however, lasts for short periods of time, and is by no means a "cure" for food allergies.

False positives generally occur due to ingestion of another food during the course of the test. If the test is taken over a long period of time, the person being tested will need to eat. While food taken during a long test should be prepared to be free of allergens, mistakes can alter the test results.

Ambiguous results occur when:

  • The patient experiences symptoms that are not typical allergy symptoms (like vomiting or heart palpitations);
  • Symptoms occur several hours or more after the allergen capsule was administered; or
  • The patient experiences a mild reaction (like hives around the mouth), especially if it cannot be repeated or does not get more severe with higher doses.

Despite these potential issues, DBPC food challenges are considered far more accurate than blood tests or prick tests.

Sources:

Niggemann, Bodo, and K. Beyer. "Pitfalls in Double-Blind Placebo-Controlled Food Challenges." Allergy July 2007 62(7):729-32. 25 Jun 2007.

Roberts, S. "Challenging Times for Food Allergy Tests." Archives of Disease in Childhood 2005(90):564-66. 25 Jun 2007.

Roberts, S. "Food Challenge Tests." Archives of Disease in Childhood 2005(90):1207-08. 25 Jun 2007.

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