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HelpTest Code BTK Bruton Tyrosine Kinase, Protein Expression, Flow Cytometry, Blood
Reporting Name
Btk Protein Flow, BUseful For
Preliminary screening for X-linked agammaglobulinemia, primarily in male patients (<65 years) or female carriers (child-bearing age: <45 years)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen 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.
Specimen Minimum Volume
2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood EDTA | Ambient | 48 hours | PURPLE OR PINK TOP/EDTA |
Reference Values
Present
Day(s) Performed
Monday through Friday
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 |
Interpretation
Results are reported as Bruton tyrosine kinase (BTK) protein expression present (normal) or absent (abnormal) in monocytes and B cells if present. Additionally, mosaic BTK expression (indicative of a carrier) and reduced BTK expression (consistent with partial BTK protein deficiency) are reported when present and correlated with a healthy experimental control.
BTK genotyping (BTKSG / Bruton Tyrosine Kinase, BTK Full Gene Analysis, Varies or FMTT / Familial Variant, Targeted Testing, Varies) should be performed in the following situations:
-To confirm any abnormal flow cytometry result
-In the rare patient with the clinical features of X-linked agammaglobulinemia, but normal BTK protein expression
-In mothers of patients who do not show the classic carrier pattern of bimodal protein expression (to determine if there is maternal germinal mosaicism or skewed altered X-chromosome inactivation), or there is dominant expression of the normal protein in the presence of one copy of a genetic variant.
Report Available
3 to 4 daysReject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
Method Name
Flow Cytometry