TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: PEANT    
Peanut, IgE with Reflex to Peanut Components, IgE, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluation of patients with suspected peanut allergy

 

Evaluation of patients with possible peanut cross-reactivity

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Testing begins with analysis of peanut IgE. If peanut IgE is undetectable (<0.10 kU/L), testing is completed.

If peanut IgE is detectable (> or =0.10 kU/L), then the 5 peanut components (Ara h 2, Ara h 1, Ara h 3, Ara h 8, and Ara h 9) are performed at an additional charge.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Peanut allergy is one of the most common food allergies in the United States, with an estimated prevalence of approximately 1% to 2%.(1) The clinical symptoms of peanut allergy may range from relatively mild, such as rhinorrhea, pruritus, or nausea, to an anaphylactic reaction that is systemic and potentially life-threatening. The diagnosis of peanut allergy is dependent upon the presence of compatible clinical symptoms in the context of peanut exposure, with support from identification of peanut-specific IgE antibodies, either by skin testing or in vitro serology testing. In vitro testing has generally focused on assessing for the presence of total peanut IgE antibodies. These antibodies are identified by immunoassay in which the capture allergen is an extract prepared from natural peanut raw material. Most studies have demonstrated a correlation between total peanut IgE antibodies and an increased likelihood of a clinical allergic response. However, some patients with significantly elevated concentrations of total peanut IgE antibodies do not have any reaction when administered a peanut oral food challenge. In some cases, this may be due to the presence of an IgE antibody specific for a nonallergenic protein present within the peanut extract. This is the basis of component allergen testing, in which the presence of IgE antibodies specific for individual proteins, namely Ara h 1, Ara h 2, Ara h 3, Ara h 8, and Ara h 9, within the peanut extract are assessed. Ara h 1, 2, and 3 are seed storage proteins, and are the most relevant for evaluation of suspected peanut allergy.(2,3) Ara h 2, in particular, has the best sensitivity and specificity for clinically relevant peanut allergic disease. Ara h 1, 2, and 3-specific IgEs also tend to be associated with more severe allergic reactions. Ara h 9 is a member of the lipid transfer protein (LTP) family. LTPs are ubiquitous throughout the plant kingdom, and are also extremely homologous. IgE antibodies specific for Ara h 9 may be associated with allergic reactions upon peanut ingestion, although published data on this is not conclusive.(4) In addition, because of the significant sequence homology, cross-reactivity of IgE antibodies may be observed between Ara h 9 and LTPs in commonly consumed plants such as peaches, apples, and plums. Lastly, Ara h 8 is a homologue of the birch pollen allergen Bet v 1. IgE antibodies against Ara h 8 are generally associated with milder peanut allergies and may be seen in the context of birch pollen sensitization.(5)

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Class

IgE kU/L

Interpretation

0

<0.10

Negative

0/1

0.10-0.34

Borderline / Equivocal

1

0.35-0.69

Equivocal

2

0.70-3.49

Positive

3

3.50-17.4

Positive

4

17.5-49.9

Strongly positive

5

50.0-99.9

Strongly positive

6

> or =100

Strongly positive

Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

Negative for total peanut IgE:

-Negative IgE results for total peanut may indicate a lack of sensitization to peanut. Because IgE antibodies specific for total peanut are not detectable, testing for peanut components is not performed.

 

Positive for total peanut IgE/negative for peanut component IgE:

-Positive IgE results for total peanut in the absence of detectable IgE responses to any peanut components may indicate a low to moderate sensitization to peanut. Correlation with patient history of allergic or anaphylactic responses to peanut is recommended.

 

Positive for total peanut IgE/positive for peanut component IgE:

-Positive IgE results to the storage proteins Ara h 1, Ara h 2, and Ara h 3 in the context of a positive IgE result for total peanut may be associated with sensitization to peanut, with increased risk for allergic reaction upon exposure to peanut, and/or with a stronger risk for a systemic reaction.

-Positive IgE results to Ara h 8 in the context of a positive IgE result for total peanut, but with negative antibodies to Ara h 1, Ara h 2, and Ara h 3, may be associated with cross-reactivity with birch and birch-related tree pollens and/or with an increased risk of a localized allergic reaction.

-Positive IgE results to Ara h 9 have been associated with both systemic and localized reactions, and with cross-reactivity to peach and peach-related fruits.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Negative results for IgE to total peanut and any peanut components do not completely exclude the possibility of clinically relevant allergic responses upon exposure to peanut. Recommend correlation of results from in vitro IgE testing with patient history of allergic or anaphylactic responses to peanut.

 

Positive results for IgE to total peanut or any peanut components are not diagnostic for peanut allergy, and only indicate patient may be sensitized to peanut or cross-reactive allergen. Recommend correlation of results from in vitro IgE testing with patient history of allergic or anaphylactic responses to peanut.

 

Testing for IgE antibodies is not useful in patients previously treated with immunotherapy to determine if residual clinical sensitivity exists, or in patients in whom the medical management does not depend upon identification of allergen specificity.  

 

False-positive results for IgE antibodies may occur in patients with markedly elevated serum IgE (>2500 kU/L) due to nonspecific binding to allergen solid phases.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Sicherer SH, Wood RA: Advances in diagnosing peanut allergy. J Allergy Clin ImmunolPract 2013;1:1-13

2. Eller E, Bindslev-Jensen C: Clinical value of component-resolved diagnostics in peanut-allergic patients. Allergy 2013;68:190-194

3. Hong X, Caruso D, Kumar R, et al: IgE, but not IgG4, antibodies to Ara h 2 distinguish peanut allergy from asymptomatic peanut sensitization. Allergy 2012;67:1538-1546

4. Klemans RJ, van Os-Medendorp H, Blankestijn M, et al: Diagnostic accuracy of specific IgE to components in diagnosing peanut allergy: a systematic review. Clin Exp Allergy 2015;45:720-730

5. Asarnoj A, Nilsson C, Lidholm J, et al: Peanut component Ara h 8 sensitization and tolerance to peanut. J Allergy Clin Immunol 2012;130:468-472

Special Instructions Library of PDFs including pertinent information and forms related to the test