Conjunctival provocation test in diagnosis of peanut allergy in children.

BACKGROUND: Peanut allergy frequently causes severe allergic reactions. Diagnosis includes detection of IgE to peanuts in serum or by skin prick tests. While children may have allergic sensitization without having clinical peanut allergy, oral peanut challenge is often required for accurate diagnosis. The conjunctival provocation test is used for diagnosis and evaluation of treatment effect in inhalant allergies, but it has not been evaluated as a tool for diagnosing peanut allergy. OBJECTIVE: To investigate whether the conjunctival provocation tests may be feasible, accurate and safe in diagnosing clinically relevant peanut allergy in patients with suspected peanut allergy. METHODS: This cross-sectional case-control study in children with clinical or laboratory suspected peanut allergy included 102 children recruited from the regional paediatric departments and specialist practices during one year from April 2011. A peanut-tolerant control group of 28 children of similar age was recruited locally. A double-blind placebo-controlled conjunctival provocation test with peanut extract was performed in all children, while oral peanut provocation was performed as double-blind placebo-controlled challenge in children with suspected peanut allergy and as an open challenge in the control children. RESULTS: All 81 children with a positive double-blind placebo-controlled oral food challenge (OFC) also had a positive conjunctival provocation test. None of the children with negative conjunctival provocation test had a positive OFC. The sensitivity and the specificity of the conjunctival provocation test were 0.96 and 0.83, respectively. No children had severe adverse reaction caused by the conjunctival provocation test, whereas 23 children suffered an anaphylactic reaction to the OFC. CONCLUSION AND CLINICAL RELEVANCE: Conjunctival allergen challenge appears to be feasible, accurate and safe in diagnosing children referred for suspected peanut allergy.

Immunoglobulin E cross-reactivity between lupine conglutins and peanut allergens in serum of lupine-allergic individuals.

BACKGROUND: Lupine is used increasingly in food products. The development of lupine allergy in peanut-allergic patients is believed to occur as a result of cross-reactivity between lupine and peanut proteins. OBJECTIVE: To investigate the degree of immunoglobulin (Ig) E cross-reactivity between allergens in lupine and peanut. METHODS: We investigated IgE cross-reactivity between lupine alpha-, beta-, gamma-, and delta-conglutins and the major peanut allergens Ara h 1, Ara h 2 and Ara h 3 using enzyme-linked immunosorbent assay with sera from patients with coexisting peanut and lupine allergy. RESULTS: Peanut proteins inhibited IgE binding towards alpha- conglutins, delta-conglutins, and, to a lesser degree, beta-conglutins, while no IgE cross-reaction with delta-conglutin was observed. Ara h 2 most potently inhibited IgE binding to lupine and delta-conglutins, while Ara h 1 most potently cross-reacted with beta-conglutin. Ara h 3 was apparently not involved in these mechanisms. CONCLUSIONS: The present study reveals IgE cross-reactivity between the 2S albumins Ara h 2 and delta-conglutin, and the 7S vicilin-like Ara h 1 and beta-conglutin, which are possibly based on homologies between phylogenetically related proteins. Ara h 2 was the most potent inhibitor of IgE binding to lupine conglutins.