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HelpTest ID DHRF Dihydrorhodamine Flow Cytometric N-Formyl-Methionyl-Leucyl-Phenylalanine Test, Blood
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
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)
Patient:
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.
Secondary ID
62766Useful For
Evaluation of RAC2 deficiency and RAC2 gain of function
Method Name
Flow Cytometry
Reporting Name
DHR Flow fMLP, BSpecimen Type
WB Sodium HeparinSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| WB Sodium Heparin | Ambient | 48 hours | GREEN TOP/HEP |
Clinical Information
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
|
Result name |
Unit |
Cutoff for defining normal |
|
% fMLP ox-DHR+ |
% |
≥10% |
|
MFI fMLP ox-DHR+ |
MFI |
≥2 |
|
Control % fMLP ox-DHR+ |
% |
≥10% |
|
Control MFI fMLP ox-DHR+ |
MFI |
≥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.
Cautions
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.
Report Available
3 to 4 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
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
86352