Test Catalog

Test Id : BLWX

Walnut-Food Components, IgE, Serum

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

Evaluation of patients with suspected walnut-food allergy to one of 2 walnut-food components

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

If total walnut-food IgE result is 0.10 kU/L or more, then walnut-food component (Jug r 1 and Jug r 3) testing is performed at an additional charge.

Method Name
A short description of the method used to perform the test

Only orderable as a reflex. For more information see BLWRF / Walnut-Food, IgE, with Reflex to Walnut-Food Components, IgE, Serum.


Fluorescent Enzyme Immunoassay (FEIA)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Walnut-Food Components, IgE, S

Lists additional common names for a test, as an aid in searching

Jug r 1

Jug r 3

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

If total walnut-food IgE result is 0.10 kU/L or more, then walnut-food component (Jug r 1 and Jug r 3) testing is performed at an additional charge.

Specimen Type
Describes the specimen type validated for testing


Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Only orderable as a reflex. For more information see BLWRF / Walnut-Food, IgE, with Reflex to Walnut-Food Components, IgE, Serum.


Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory


Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
Frozen 90 days

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

Evaluation of patients with suspected walnut-food allergy to one of 2 walnut-food components

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

If total walnut-food IgE result is 0.10 kU/L or more, then walnut-food component (Jug r 1 and Jug r 3) testing is performed at an additional charge.

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

Allergies to tree nuts are relatively prevalent and can result in severe reactions. The main culprits in tree nut allergies include walnut, almond, pistachio, cashew, pecan, hazelnut, macadamia, Brazil nut, and pine nuts. Tree nut allergy often appears in young children and estimates of prevalence range from 0.1% to greater than 5% of the population, dependent on geographical region.


In the case of nut-induced allergic reactions, as with many other foods, symptoms usually present within minutes of ingestion. Over 80% of reactions to tree nuts involve allergy related respiratory symptoms. Tree nut allergies are one of the most dangerous types of allergic reaction with 20% to 40% of cases of related anaphylaxis and 70% to 90% of fatalities attributable to nut exposure (including peanut exposure).


Walnut is a relatively common cause of allergic reactions to tree nuts. with an overall population occurrence of 0.7%. Allergy to walnut is often persistent over a lifetime and can be severe. Walnuts can cause sensitization by means of walnut pollens/dust particles in processing industries. Allergy related common symptoms observed are nausea, vomiting, pruritus, abdominal pain urticaria, angioedema, diarrhea, asthma, and anaphylaxis. Walnuts and pecans are related species and there is significant potential for cross-reactively between them.


Jug r 1 is a prevalent component protein associated with systemic walnut allergy. In a study observed among patients with systemic allergic reactions to walnuts (n=16), 75% showed IgE binding to Jug r 1 Jug r 1 is the most specific and has the highest positive predictive value for walnut allergic and thus is considered the major component protein for walnut allergy diagnosis. than other walnut food allergenic components. Jug r 1 is the major component considered for diagnosing allergy to walnut. It is a persistent storage protein component (2s albumin), that is both heat and digestion stable. Cross-reactivity of 2S albumins with those of other plant sources, such as black walnut, Brazil nut, pecan, mustard, Corylus (common hazel), and sesame, may occur.


Jug r 3 is a lipid transport protein (LTP), that is also a major allergen in walnut. This protein is also resistant to heat/digestion. This component allergen is associated with the risk of severe reactions (food-induced contact urticaria, oral allergy syndrome, gastrointestinal symptoms, and anaphylaxis). Approximately 75% of individuals with walnut allergy show reactivity to this component.


Significant association of the presence of IgE antibodies between Jug r 3 (walnut) and Cor a 8 (hazelnut) suggests potential for co-sensitization. Other foods that also contain LTP proteins, such as peach, cherry, hazelnut, almond, and peanut (Ara h 9 component) may also exhibit cross reactivity and co-sensitization to individuals with IgE antibodies against Jug r 3.


Positive antibody to total walnut specific testing may be observed with concurrent negative Jug r 1 and Jug r 3 component protein antibody testing may occur when there is sensitization to other walnut component proteins and/or pollens containing profilins and other proteins.

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.

Only orderable as a reflex. For more information see BLWRF / Walnut-Food, IgE, with Reflex to Walnut-Food Components, IgE, Serum.



IgE kU/L



















Strongly positive



Strongly positive


> or =100

Strongly positive

Concentrations of 0.70 kU/L or more (class 2 and above) will flag as abnormally high.

Reference values apply to all ages.

Provides information to assist in interpretation of the test results

When detectable total walnut-food IgE antibody is present (> or =0.10 IgE kUa/L), additional specific component IgE antibody testing will be performed. If at least one potential specific allergenic walnut-food component IgE is detectable (> or =0.10 IgE kUa/L), an interpretive report will be provided.


When the sample is negative for total walnut-food IgE antibody (<0.10 IgE kUa/L), further testing for specific walnut-food component IgE antibodies will not be performed. Negative IgE results for total walnut-food antibody may indicate a lack of sensitization to potential walnut-food allergenic components.

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

Clinical correlation of results from in vitro IgE testing with patient history of allergic or anaphylactic responses to walnuts is recommended.


Negative results for IgE antibodies to walnut and walnut allergenic components do not completely exclude the possibility of clinically relevant allergic responses upon exposure.


Positive results for IgE antibodies to walnut or any potential walnut allergenic components are not diagnostic for walnut allergy and only indicate patient may be sensitized to walnut or a cross-reactive allergen.


Testing for IgE antibodies may not be useful in patients previously treated with immunotherapy to determine if residual clinical sensitivity exists or in patients whose medical management does not depend upon the 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.


Cross-reacting carbohydrate determinants may also result in positive total walnut specific IgE testing.

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

1. Salo PM, Arbes SJ Jr, Jaramillo R, et al. Prevalence of allergic sensitization in the United States: results from the National Health and Nutrition Examination Survey (NHANES) 2005-2006. J Allergy Clin Immunol. 2014;134(2):350-359

2. Waserman S, Watson W. Food allergy. Allergy Asthma Clin Immunol. 2011;7 Suppl 1(Suppl 1):S73. Abrams EM, Sicherer SH. Diagnosis and management of food allergy. CMAJ. 2016;188(15):1087-1093

4. Weinberger T, Sicherer S. Current perspectives on tree nut allergy: a review. J Asthma Allergy. 2018;11:41-51

5. Lomas JM, Jarvinen KM. Managing nut-induced anaphylaxis: challenges and solutions. J Asthma Allergy. 2015;8:115-123

6. Maloney JM, Rudengren M, Ahlstedt S, Bock SA, Sampson HA. The use of serum-specific IgE measurements for the diagnosis of peanut, tree nut, and seed allergy. J Allergy Clin Immunol. 2008;122(1):145-151

7. Sicherer SH, Burks AW, Sampson HA. Clinical features of acute allergic reactions to peanut and tree nuts in children. Pediatrics. 1998;102(1):e6

8. Crespo JF, James JM, Fernandez-Rodriguez C, Rodriguez J. Food allergy: nuts and tree nuts [published correction appears in Br J Nutr. 2008 Feb;99(2):447-8]. Br J Nutr. 2006;96 Suppl 2:S95-S102

9. Yang L, Clements S, Joks R. A retrospective study of peanut and tree nut allergy: Sensitization and correlations with clinical manifestations [published online ahead of print, 2015 Feb 27]. Allergy Rhinol (Providence). 2015;doi:10.2500/ar.20105.6.0108

10. Pastorello EA, Farioli L, Pravettoni V, et al. Lipid transfer protein and vicilin are important walnut allergens in patients not allergic to pollen. J Allergy Clin Immunol. 2004;114(4):908-914

11. Rosenfeld L, Shreffler W, Bardina L, et al. Walnut allergy in peanut-allergic patients: significance of sequential epitopes of walnut homologous to linear epitopes of Ara h 1, 2 and 3 in relation to clinical reactivity. Int Arch Allergy Immunol. 2012;157(3):238-245

12. Masthoff LJ, Hoff R, Verhoeckx KC, et al. A systematic review of the effect of thermal processing on the allergenicity of tree nuts. Allergy. 2013;68(8):983-993

13. Costa J, Carrapatoso I, Oliveira MB, Mafra I. Walnut allergens: molecular characterization, detection and clinical relevance. Clin Exp Allergy. 2014;44(3):319-341

14. Valcour A, Lidholm J, Borres MP, Hamilton RG. Sensitization profiles to hazelnut allergens across the United States. Ann Allergy Asthma Immunol. 2019;122(1):111-116.e1

15. Asero R, Piantanida M, Pravettoni V. Allergy to LTP: to eat or not to eat sensitizing foods? A follow-up study. Eur Ann Allergy Clin Immunol. 2018;50(4):156-162

Method Description
Describes how the test is performed and provides a method-specific reference

Specific IgE from the patient's serum reacts with the allergen of interest, which is covalently coupled to an ImmunoCAP. After washing away nonspecific IgE, enzyme-labeled anti-IgE antibody is added to form a complex. After incubation, unbound anti-IgE is washed away, and the bound complex is then incubated with a developing agent. After stopping the reaction, the fluorescence of the eluate is measured. Fluorescence is proportional to the amount of specific IgE present in the patient's sample (ie, the higher the fluorescence value, the more IgE antibody is present).(Package insert: ImmunoCAP System Specific IgE FEIA. Phadia; Rev 06/2020)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

86008 x2

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
BLWX Walnut-Food Components, IgE, S 63486-5
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
INBLW Walnut-Food IgE Ab Interpretation 69048-7
R1JUG Jug r 1 (Walnut-Food), IgE, S 81790-8
R3JUG Jug r 3 (Walnut Extract), IgE, S 81789-0

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | PHP Pdf | CMS Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports