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Peanut Component Panel.

Peanut Component Panel

Test Summary

Peanut Component Panel

  

Clinical Use

  • Assess risk of severe allergic reaction vs mild or localized reaction to peanut exposure

Clinical Background

The prevalence of peanut allergy in North American school-aged children is approximately 1%.1 This allergy is often a lifelong condition,2 and is the most common food-related cause of fatal allergic reactions in Western countries.3 Peanut allergy is typically diagnosed based on clinical history and peanut sensitization (ie, IgE antibody response to peanut extract during blood or skin prick testing). Sensitization, however, does not correlate with allergic symptoms in a large percentage of patients,4,5 and as many as 77% of peanut sensitized patients may not be at risk for a systemic reaction.6 This may be because most tests are based on crude natural peanut extracts that contain allergenic and non-allergenic components, and some of these components may crossreact with pollen or other allergens.

Over 13 allergenic components have been identified in peanuts.7 Of these, Ara h 1, 2, 3, 6, 8, and 9 are considered the most important markers of peanut sensitization and are predictive of an allergic response. Ara h 1, 2, and 3 are seed storage proteins, and sensitization to them is associated with a high risk of a systemic allergic reaction: 87% of the children with IgE reactivity have allergic symptoms, including anaphylaxis.8 Ara h 2 is a more important predictor of clinical peanut allergy than Ara h 1 and 3, and is the one most often associated with severe reactions.6 Ara h 6 sensitization is associated with IgE antibodies that crossreact with Ara h 29; rarely does sensitization to Ara h 6 occur in the absence of sensitization to Ara h 2.10

Ara h 8 is a pathogenesis-related (PR)-10 protein, and sensitization to it is associated with a low risk of systemic reaction and a moderate risk of mild, localized symptoms (ie, oral allergy syndrome). In a study of 144 children with IgE antibodies to Ara h 8 (but not Ara h 1-3), 89% were either peanut consumers or did not react to an oral food challenge with peanuts, while 9.7% of the children had mild oral cavity symptoms and 1 child developed mild gastrointestinal symptoms.11 Ara h 8 crossreacts with pollens (eg, Birch and Birch-related tree pollen); Mittag et al showed that 20 patients with Birch pollen allergy and IgE antibodies to Ara h 8 exhibited oral allergy syndrome when exposed to peanut.12

Ara h 9 is a lipid transfer protein, and sensitization to it can result in systemic reactions, including anaphylaxis; 38% (6/16) of subjects sensitized to Ara h 9 were found to have severe symptoms after peanut exposure.9 People sensitized to Ara h 9 are often also sensitized to Ara h 1-3.13 Ara h 9 is not specific to peanut; it crossreacts with fruits with pits (eg, peaches).14

The Peanut Component Panel tests for IgE antibodies to peanut allergens Ara h 1, 2, 3, 8, and 9. Identifying sensitization to peanut component allergens can assist is assessing a patient’s risk for a severe systemic reaction.

Individuals Suitable for Testing

  • Individuals with a history of peanut sensitivity or with documented sensitization by blood or pin prick testing

Method

  • Fluorescent enzyme immunoassay (FEIA) measurement of IgE antibodies to Ara h 1 (f422), Ara h 2 (f423), Ara h 3 (f424), Ara h 8 (f352), and Ara h 9 (f427)

  • Analytical sensitivity: <0.1 kU/L

Interpretive Information

Reactivity to Ara h 1, 2, or 3 is associated with a high risk for systemic reaction, including anaphylaxis. Reactivity to Ara h 9 is associated with a variable risk for systemic reaction, including anaphylaxis. Patients who exhibit reactivity to Ara h 1, 2, 3, and/or 9 should be counseled to avoid peanuts, foods that contain peanut products, and foods that have been processed in plants that also process peanuts.

Reactivity to Ara h 8 and nonreactivity to Ara h 1, 2, 3, and 9 indicates a low risk of a systemic allergic reaction. Patients with only Ara h 8 sensitization may consider taking an oral food challenge test, and, if negative, they may not have to avoid peanuts or peanut-containing foods.15

As with all diagnostic testing, results should be interpreted in light of a patient’s history, physical examination, and results of other diagnostic testing.

References

  1. Sicherer SH, Munoz-Furlong A, Burks AW, et al. Prevalence of peanut and tree nut allergy in the US determined by a random digit dial telephone survey. J Allergy Clin Immunol. 1999;103:559-562.

  2. Wood RA. The natural history of food allergy. Pediatrics.2003;111:1631-1637.

  3. Bock SA, Munoz-Furlong A, Sampson HA. Further fatalities caused by anaphylactic reactions to food, 2001–2006. J Allergy Clin Immunol. 2007;119:1016-1018.

  4. Wainstein BK, Yee A, Jelley D, et al. Combining skin prick, immediate skin application and specific-IgE testing in the diagnosis of peanut allergy in children. Pediatr Allergy Immunol. 2007;18:231- 239.

  5. Ostblom E, Lilja G, Ahlstedt S, et al. Patterns of quantitative food-specific IgE-antibodies and reported food hypersensitivity in 4-year-old children. Allergy. 2008;63:418-424.

  6. Nicolaou N, Poorafshar M, Murray C, et al. Allergy or tolerance in children sensitized to peanut: prevalence and differentiation using component-resolved diagnostics. J allergy Clin Immunol. 2010;125:191-197.e1-13.

  7. Allegome database. Available at: http://www.allergome.org/index.php. Accessed August 28, 2013.

  8. Asarnoj A, Movérare R, Ostblom E et al. IgE to peanut allergen components: relation to peanut symptoms and pollen sensitization in 8-year-olds. Allergy. 2010;65:1189-1195.

  9. Chen X, Wang Q, El-Mezayen R, et al. Ara h 2 and Ara h 6 have similar allergenic activity and are substantially redundant. Int Arch Allergy Immunol. 2013;160:251-258.

  10. Asarnoj A, Glaumann S, Elfström L, et al. Anaphylaxis to peanut in a patient predominantly sensitized to Ara h 6. Int Arch Allergy Immunol. 2012;159:209-212.

  11. Asarnoj A, Nilsson C, Lidholm J, et al. Peanut component Ara h8 sensitization and tolerance to peanut. J Allergy Clin Immunol. 2012;130:468-472.

  12. Mittag D, Akkerdaas J, Ballmer-Weber BK, et al. Ara h 8, a Bet v1-homologous allergen from peanut, is a major allergen in patients with combined birch pollen and peanut allergy. J Allergy Clin Immunol. 2004;114:1410-1417.

  13. Movérare R, Ahlstedt S, Bengtsson U, et al. Evaluation of IgE antibodies to recombinant peanut allergen in patients with reported reactions to peanut. Int Arch Allergy Immunol. 2011;156:282-290.

  14. Lauer I, Dueringer N, Pokoj S, et al. The non-specific lipid transfer protein, Ara h 9, is an important allergen in peanut. Clin Exp Allergy. 2009;39:1427-1437.

  15. Eckman J, Saini SS, Hamilton RG. Diagnostic evaluation of food-related allergic diseases. Allergy Asthma Clin Immunol. 2009;5:2. doi: 10.1186/1710-1492-5-2.
     

 Content reviewed 09/2013

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