Test Catalog

Test Id : DHRF

Dihydrorhodamine Flow Cytometric N-Formyl-Methionyl-Leucyl-Phenylalanine Test, Blood

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

Evaluation of RAC2 deficiency and RAC2 gain of function

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

Flow Cytometry

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

DHR Flow fMLP, B

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

Neutrophil Oxidative Burst (NOXB)

Nitroblue Tetrazolium (NBT) Assay


Dihydrorhodamine (DHR)

Neutrophil Function

Rac2 deficiency

Specimen Type
Describes the specimen type validated for testing

WB Sodium Heparin

Shipping Instructions

Specimens are required to be received in the laboratory weekdays and by 4 p.m. on Friday. Collect and package specimen as close to shipping time as possible. Ship specimen overnight in an Ambient Shipping Box-Critical Specimens Only (T668) following the instructions in the mailer.


It is recommended that specimens arrive within 24 hours of collection.


Samples arriving on the weekend and observed holidays may be canceled.

Necessary Information

Ordering physician name and phone number are required.

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

Both a whole blood sodium heparin specimen and a whole blood sodium heparin control specimen from an unrelated, healthy donor are required.


Supplies: Ambient Shipping Box-Critical Specimens Only (T668)



Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.


Normal Control:

Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Collection Instructions:

1. Collect a control specimen from a normal (healthy), unrelated person within an hour of the patient's specimen collection time.

2. Label clearly on outermost label normal control.

3. Send whole blood specimen in original tube. Do not aliquot.

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

1 mL

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

Gross hemolysis Reject
Gross lipemia 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
WB Sodium Heparin Ambient 48 hours GREEN TOP/HEP

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

Evaluation of RAC2 deficiency and RAC2 gain of function

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

This assay can be used for the diagnostic evaluation of RAC2 deficiency, which is a neutrophil defect that causes profound neutrophil dysfunction with decreased chemotaxis, polarization, superoxide anion production, azurophilic granule secretion. This disease is caused by inhibitory variants in the RAC2 gene, which encodes a Rho family GTPase essential to neutrophil activation and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase function.(1) Patients with RAC2 deficiency have been shown to have normal neutrophil oxidative burst when stimulated with phorbol myristate acetate (PMA), indicating normal NADPH oxidase activity, but abnormal neutrophil responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), which is a physiological activator of neutrophils. The defective oxidative burst to fMLP, but not to PMA, is consistent with RAC2 deficiency.(2) By contrast, gain of function variants in RAC2 would lead to a an exaggerated response to fMLP.(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.

Result name


Cutoff for defining normal

% fMLP ox-DHR+


> or =10%



> or =2

Control % fMLP ox-DHR+


> or =10%

Control MFI fMLP ox-DHR+


> or =2


fMLP = N-formyl-methionyl-leucyl-phenylalanine

DHR = dihydrorhodamine

MFI = mean fluorescence intensity


The appropriate age-related reference values for Absolute Neutrophil Count will be provided on the report.

Provides information to assist in interpretation of the test results

An interpretive report will be provided, in addition to the quantitative values described in Clinical Information.


Interpretation of the results of the quantitative dihydrorhodamine (DHR) flow cytometric assay has to include both the proportion of positive neutrophils for DHR after N-formyl-methionyl-leucyl-phenylalanine stimulation, and the mean fluorescence intensity.

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

Specimens are optimally tested within 24 hours of blood draw, though the stability of the assay is within 48 hours of collection. Specimens should be collected in sodium heparin and transported under strict ambient conditions. Use of the Ambient Mailer-Critical Specimens Only box (T668) is encouraged to ensure appropriate transportation of the specimen.


Hemolyzed specimens may give high background. Specimens with an absolute neutrophil count below 200 will not be accepted for this assay. Complete myeloperoxidase deficiency can yield a false-positive result.

Supportive Data

Dihydrorhodamine analysis was performed to assess neutrophil oxidative burst in 157 healthy donors, 74 children, and 83 adults.

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

1. Ambruso DR, Knall C, Abell AN, et al: Human neutrophil immunodeficiency syndrome is associated with an inhibitory Rac2 mutation. Proc Natl Acad Sci U S A. 2000 Apr 25;97(9):4654-4659

2. Accetta D, Syverson G, Bonacci B, et al: Human phagocyte defect caused by a RAC2 mutation detected by means of neonatal screening for T cell lymphopenia. J Allergy Clin Immunol. 2011 Feb;127(2):535-538

3. Hsu AP, Donko A, Arrington ME, et al: Dominant activating RAC2 mutation with lymphopenia, immunodeficiency, and cytoskeletal defects. Blood. 2019 May 2;133(18):1977-1988

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

A sodium heparin whole blood specimen is incubated at 37 degrees C in the presence of DHR123. N-formyl-methionyl-leucyl-phenylalanine (fMLP) stimulant is added and mixed with the whole blood specimen for additional incubation at 37 degrees C. The sample is then centrifuged, and cell pellet is subsequently lysed with ammonium chloride at room temperature. Lysed samples are then washed with azide-free phosphate buffered saline prior to staining with LIVE/DEAD viability marker and CD15 at ambient temperature. Finally, cells are washed, centrifuged, and resuspended in 1% paraformaldehyde prior to analysis. Viable neutrophils are identified by the use of the viability dye and further confirmed by the presence of CD15. Approximately 20,000 viable neutrophil events in the unstimulated sample are used to set the limits for number of events collected for flow cytometry. The results are derived as delta % DHR+ neutrophils after fMLP stimulation and mean fluorescence intensity.(O'Gorman MR, Corrochano V: Rapid whole-blood flow cytometry assay for diagnosis of chronic granulomatous disease. Clin Diagn Lab Immunol 1995;2[2]:227-232; Kuhns DB: Diagnostic testing for chronic granulomatous disease. Methods Mol Biol. 2019;1982:543-571)

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


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.

3 to 4 days

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

4 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 Regional Manager. 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 using an analyte specific reagent. Its performance characteristics were 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
DHRF DHR Flow fMLP, B 98123-3
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.
ANC Absolute Neutrophil Count 751-8
FMPPP % FMLP ox-DHR+ 85373-9
FMPM MFI fMLP ox-DHR+ 85370-5
ANCC Control Absolute Neutrophil Count 85369-7
FMPPC Control % fMLP ox-DHR+ 85372-1
FMPMC Control MFI fMLP ox-DHR+ 85371-3
DHRFI Interpretation 69052-9

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