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HelpTest Code BTK Bruton Tyrosine Kinase, Protein Expression, Flow Cytometry, Blood
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Reporting Name
Btk Protein Flow, BSpecimen Type
Whole Blood EDTAOrdering Guidance
Bruton tyrosine kinase (BTK) protein and genetic tests are not meant for patients with hematological neoplasias on kinase inhibitor therapy, including but not restricted to the selective BTK inhibitor, ibrutinib. This test is only meant for the assessment of patients with a suspected monogenic primary immunodeficiency, X-linked agammaglobulinemia, caused by germline variants in the Bruton tyrosine kinase gene.
The preferred test for confirming a diagnosis of X-linked agammaglobulinemia in male patients and identifying female carriers is BTKSG / Bruton Tyrosine Kinase, BTK Full Gene Analysis, Varies.
In families where a BTK variant has already been identified, order FMTT / Familial Variant, Targeted Testing, Varies.
Shipping Instructions
Testing is not performed on Saturday, Sunday, or observed holidays. Only collect and ship specimen for arrival on days when testing is performed.
Specimens received on days when testing is not performed or after 5 p.m. Central on Friday may be canceled if specimen is outside of stability when testing is next performed.
Collect and package specimen as close to shipping time as possible. It is recommended that specimens arrive within 24 hours of collection.
Necessary Information
Ordering healthcare professional name and phone number are required.
Specimen Required
Container/Tube: Lavender top (EDTA)
Specimen Volume: 4 mL
Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood EDTA | Ambient | 48 hours | PURPLE OR PINK TOP/EDTA |
Specimen Minimum Volume
2 mL
Day(s) Performed
Monday through Friday
Specimen Retention Time
4 daysReport Available
3 to 4 daysReference Values
Present
Useful For
Preliminary screening for X-linked agammaglobulinemia, primarily in male patients (<65 years) or female carriers (child-bearing age: <45 years)
CPT Code Information
88184
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| BTK | Btk Protein Flow, B | 75708-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 89011 | Btk Protein Flow, B | 75708-8 |
Method Description
The Bruton tyrosine kinase (BTK) protein expression screening assay is performed on a whole blood sample. The cells in the blood are stained with antihuman CD20 (B cells) and CD14 (monocytes) antibodies followed by red blood cell lysis (using a premade Lysis buffer), cell fixation, and permeabilization to prepare the cell membrane for the anti-human BTK antibody. After the permeabilization step, the cells are stained for intracellular BTK using antihuman BTK-fluorescent pre-conjugated antibody. After the staining and wash process, the cells are fixed and analyzed by multiparametric flow cytometry.(Unpublished Mayo method)
Disease States
- Humoral immunodeficiency
- Common variable immunodeficiency
Genetics Test Information
The Bruton tyrosine kinase (BTK) gene is present on the long arm of the X-chromosome and encodes the intracellular signaling protein BTK critical for B-lymphocyte development and function. Loss of function variants in this gene cause X-linked agammaglobulinemia in male patients.