Test Catalog

Test Id : EDN

Eosinophil Derived Neurotoxin, Serum

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

Evaluating patients suspected to have a condition associated with eosinophilia or hypereosinophilia


Evaluating patients with elevated peripheral blood eosinophil counts


Managing patients with elevated eosinophil-derived neurotoxin in the context of eosinophil-associated diseases

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

Fluorescence 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

Eosinophil Derived Neurotoxin, S

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




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


Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial within 12 hours of collection. Serum cannot sit on either gel or cells for longer than 12 hours.

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

0.3 mL

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
Heat-treated specimen Reject
If serum is on cell pellet or gel for >12 hours Reject

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) 7 days
Frozen 21 days

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

Evaluating patients suspected to have a condition associated with eosinophilia or hypereosinophilia


Evaluating patients with elevated peripheral blood eosinophil counts


Managing patients with elevated eosinophil-derived neurotoxin in the context of eosinophil-associated diseases

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

Eosinophils are a type of white blood cell (WBC) that derives from myeloid progenitor cells.(1) They are a critical part of the immune response to helminth and other infections and play a significant role in allergic diseases. Eosinophils are characterized by their cytoplasmic granules, which appear dark-red when stained with eosin. These cytoplasmic granules contain a number of cytotoxic proteins, including major basic protein, eosinophil cationic protein, and eosinophil-derived neurotoxin (EDN). Upon activation, eosinophils degranulate, with subsequent release of these proteins into the extracellular space. These proteins exhibit a variety of activities, with EDN being a ribonuclease having antiviral activity. Eosinophils generally comprise less than 5% of the total WBC count. Eosinophilia and hypereosinophilia are defined by elevated numbers of eosinophils in the peripheral blood at 500/mcL and above and 1500/mcL and above, respectively. Apart from situations of a normal immune response, elevated eosinophil numbers can be found in allergy, asthma, malignancies, immunodeficiencies, autoimmune diseases, and eosinophilic disorders. In some cases, peripheral blood eosinophil counts may not accurately reflect elevated numbers of eosinophils found in tissues; absolute counts also do not indicate the level of eosinophil activation and degranulation. EDN concentrations have been shown to correlate with peripheral blood eosinophil counts and may provide additional information related to activation status.(2,3)

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.

<70 mcg/L: Normal

70-99 mcg/L: Borderline

> or =100 mcg/L: Elevated

Provides information to assist in interpretation of the test results

Eosinophil-derived neurotoxin (EDN) concentrations greater than or equal to 100 mcg/L, in the presence of elevated numbers of peripheral blood or tissue-resident eosinophils, may be suggestive of inflammation and/or increased disease activity in patients with eosinophil-associated diseases.


In the context of normal eosinophil counts, EDN concentrations greater than 70 mcg/L may indicate cellular activation and degranulation.


In the context of elevated eosinophil counts, EDN concentrations less than or equal to 70 mcg/L may indicate limited or absent cellular activation.

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

Prolonged contact of serum with the cell pellet can lead to increased concentrations of serum eosinophil-derived neurotoxin (EDN). Serum should be aliquoted into a plastic vial immediately (within 12 hours) after centrifugation.


Elevated concentrations of EDN are not diagnostic for any specific condition and should be correlated with other laboratory data and clinical information.


Normal EDN concentrations do not exclude the possibility of eosinophilia or hypereosinophilia

Supportive Data

An internal study evaluated the correlation between serum eosinophil-derived neurotoxin (EDN) concentrations and peripheral blood eosinophil counts. A cohort of samples that spanned the measuring range for absolute eosinophil counts were collected (n=110). When samples were stratified according to clinical cutoffs for eosinophil counts, a significant difference in EDN concentrations between normal (median: 43.8, 95% CI: 32.8–54.0 mcg/L, n=40) and elevated (median: 120.0, 95% CI: 95.4–149.0 mcg/L, n=70) groups (p<0.0001) was observed. Moreover, the three samples that were considered hypereosinophilic (>1.5 x 10(9) cells/L) all had very high concentrations of EDN (median: 200 mcg/L). A receiver operating characteristic (ROC) analysis demonstrated an area under the curve of 0.841 in assessing overall sensitivity and specificity of EDN for eosinophilia. Based on the ROC curve, borderline and abnormal cutoffs were selected at 70 mcg/L and 100 mcg/L, respectively. Both cutoffs demonstrated a specificity of 85% for eosinophilia. However, the cutoff of 70 mcg/L had an improved sensitivity of 74.3% compared to 100 mcg/L with a sensitivity of 57.1%.

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

1. Wechsler ME, Munitz A, Ackerman SJ, et al: Eosinophils in health and disease: A state-of-the-art review. Mayo Clin Proc. 2021 Oct;96(10):2694-2707

2. Rutten B, Young S, Rhedin M, et al: Eosinophil-derived neurotoxin: A biologically and analytically attractive asthma biomarker. PLoS ONE. 2021 Feb 10;16(2):e0246627

3. Rydell N, Nagao M, Ekoff H, et al: Development of an automated ImmunoCAP research assay for eosinophil derived neurotoxin and its use in asthma diagnosis in children. Pract Lab Med. 2019 Sep 19;17:300138

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

Anti-eosinophil derived neurotoxin (EDN) antibodies, covalently bound to lmmunoCAP, bind to EDN in the patient sample. After washing, enzyme labeled antibodies against EDN are added to form a complex. Following incubation, the unbound enzyme labelled anti-EDN antibodies are washed away, and the bound complex is incubated with a developing agent. After the reaction has been stopped, the fluorescence of the eluate is measured. The response value correlates to the amount of EDN in the sample and a calibration curve is used to transform the response values to concentrations.(Package insert: Phadia ImmunoCAP EDN Assay Kit. Thermo Scientific; Rev 9/2020)

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.


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.

2 to 8 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


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their account representative. For assistance, contact Customer Service.

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 was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

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.


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
EDN Eosinophil Derived Neurotoxin, S 100976-0
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.
EDN Eosinophil Derived Neurotoxin, S 100976-0

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 | 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

Test Update Resources

Change Type Effective Date
New Test 2022-12-15