NIH Guidelines for the diagnosis and: management of FA (2010)------------------
"Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel"
http://www.jacionline.org/article/S0091-6749(10)01566-6/fulltext------------------
4.2.2.8. Oral food challenges
Guideline 11: The EP recommends using oral food challenges for diagnosing FA. The DBPCFC is the gold standard. However, a single-blind or an open-food challenge may be considered diagnostic under certain circumstances: if either of these challenges elicits no symptoms (ie, the challenge is negative), then FA can be ruled out; but when either challenge elicits objective symptoms (ie, the challenge is positive) and those objective symptoms correlate with medical history and are supported by laboratory tests, then a diagnosis of FA is supported.
Rationale: DBPCFC is the most specific test for diagnosing FA. However, due to the expense and inconvenience of DBPCFCs, single-blind and open-food challenges may be used in the clinical setting.
Balance of benefits and harms: The DBPCFC markedly reduces potential bias of patients and supervising health care professionals that may interfere with the appropriate interpretation of oral food challenges, and corresponds most closely to the natural ingestion of food. Other diagnostic tests lack specificity and may lead to the unnecessary exclusion of foods from patients' diets. However, the DBPCFC is time consuming, expensive, and, like any form of oral food challenge, subjects the patient to potential severe allergic reactions. Single-blind and open-food challenges are frequently used to screen patients for FA. When negative, they may be considered diagnostic in ruling out FA, and when positive (ie, when “immediate” objective allergic symptoms are elicited), they may be considered diagnostic in patients who have a supportive medical history and laboratory data.
Quality of evidence: High
Contribution of expert opinion: Moderate
Note: Because of the inherent risk, an oral food challenge must be conducted at a medical facility that has onsite medical supervision and appropriate medicines and devices on hand.
A positive SPT or sIgE test result is indicative of allergic sensitization, but these findings alone may or may not be clinically relevant. Most investigators in the field agree that verification of clinical reactivity requires well-designed oral food challenge testing.102, 103, 129, 130, 131, 132, 133
Prior to initiating an oral food challenge, suspected foods are eliminated from the diet for 2 to 8 weeks, depending on the type of food-induced allergic reaction being examined (for example, urticaria vs EoE).133, 134 All foods in question must be strictly avoided simultaneously. An infant's diet can be limited to a hypoallergenic formula. For exclusively breast-fed infants, either the suspected food is eliminated from the mother's diet or the baby is fed a hypoallergenic formula until the allergic food is identified.
After documenting significant improvement on dietary elimination, the challenge test is carried out while the patient is on minimal or no symptomatic medication. The test should be designed and performed under medical supervision to document the dose that provokes the reaction and to administer symptomatic treatment, which may require management of anaphylaxis (section 6), and the medical personnel should have experience in carrying out such challenges. Oral food challenge begins with a low dose (intended to be lower than a dose that can induce a reaction135, 136). While monitoring for any allergic symptoms, the dose is gradually increased, until a cumulative dose at least equivalent to a standard portion for age is consumed. The challenge may be carried out in an open fashion in infants, but in older children, single-blind food challenges or DBPCFCs may be necessary to minimize patient and physician bias.
Using DBPCFC, several studies have shown that only about one third of the suspected foods are found to be truly allergic.103 In addition to verifying FA, challenge testing prevents unnecessary dietary avoidance and enhances compliance with the elimination diet. Nevertheless, because of the risk of a severe reaction, intentional challenge should be avoided in patients who have recently experienced a life-threatening reaction to a particular food, particularly if it occurred more than once. In the case of post-prandial exercise-induced reactions, food challenge should be followed by exercise.92
There is currently no internationally accepted, standardized protocol for performing and interpreting DBPCFCs, although reviews outlining benefits and deficiencies have been published.133, 135, 136, 137
Topic: What constitutes a "FAIL"? (Read 4112 times)
