TRBC1 a Useful Tool in T-Cell Flow Cytometry [Test in Focus]
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Flow cytometry is a well-established method that is utilized to assist in the characterization of mature T-cell neoplasms and lymphoproliferations, but the markers used by individual laboratories can vary. In this "Test in Focus," Horatiu Olteanu, M.D., Ph.D., gives an overview of the new T-cell receptor (TCR) β-chain constant region (TRBC1) flow cytometry marker, which is now included in Mayo Clinic Laboratories' routine diagnostic T-cell flow cytometry panel. He discusses when this testing should be ordered, how the addition of TCRBC1 compares to previous testing approaches, and how this marker can assist ordering physicians.
Testing
Useful for:
- Evaluating lymphocytoses of undetermined etiology
- Identifying T-cell lymphoproliferative disorders involving blood and bone marrow
- Distinguishing reactive lymphocytes and lymphoid hyperplasia from malignant lymphoma
- Distinguishing between malignant lymphoma and acute leukemia
- T-cell large granular lymphocytic leukemia, peripheral T-cell lymphoma, not otherwise specified, anaplastic large T-cell lymphoma, angioimmunoblastic T-cell lymphoma, Sezary syndrome / mycosis fungoides, and certain T-lymphoblastic leukemia/lymphoma, among others.
Specimen Requirements
Specimen Type
Varies
Specimen Required
Submit only 1 of the following specimens:
Specimen Type: Blood
Container/Tube:
Preferred: Yellow top (ACD solution A or B)
Acceptable: Green top (sodium heparin) or lavender top (EDTA)
Specimen Volume: 6 mL
Slides: Include 5 to 10 unstained blood smears, if possible.
Collection Instructions:
1. Send specimen in original tube. Do not transfer blood to other containers.
2. Label specimen as blood.
Specimen Stability Information: Ambient <96 hours/Refrigerated < or =96 hours
Specimen Type: Bone marrow
Container/Tube:
Preferred: Yellow top (ACD solution A or B)
Acceptable: Green top (sodium heparin) or lavender top (EDTA)
Specimen Volume: 1-5 mL
Slides: Include 5 to 10 unstained bone marrow aspirate smears, if possible.
Collection Instructions:
1. Submission of bilateral specimens is not required.
2. Label specimen as bone marrow.
Specimen Stability Information: Ambient <96 hours/Refrigerated < or =96 hours
Specimen Type: Fluid
Sources: Serous effusions, pleural fluid, pericardial fluid, abdominal (peritoneal) fluid
Container/Tube: Body fluid container
Specimen Volume: 20 mL
Collection Instructions:
1. If possible, fluids other than spinal fluid should be anticoagulated with heparin (1 U/mL of fluid).
2. The volume of fluid necessary to phenotype the lymphocytes or blasts in serous effusions depends upon the cell count in the specimen. Usually 20 mL of pleural or peritoneal fluid is sufficient. Smaller volumes can be used if there is a high cell count.
3. Label specimen with fluid type.
Specimen Stability Information: Refrigerated <72 hours/Ambient < or =72 hours
Specimen Type: Spinal fluid
Container/Tube: Sterile vial
Specimen Volume: 1-1.5 mL
Collection Instructions:
1.An original cytospin preparation (preferably unstained) must be included with the spinal fluid specimen so correlative morphologic evaluation can occur.
2. The volume of fluid necessary to phenotype the lymphocytes or blasts in spinal fluid depends upon the cell count in the specimen. A cell count should be determined and submitted with the specimen. Usually 1 to 1.5 mL of spinal fluid is sufficient. Smaller volumes can be used if there is a high cell count. If cell count is <10 cells/mcL, a larger volume of spinal fluid may be required. When cell counts drop below 5 cells/mcL, the immunophenotypic analysis may not be successful.
3. Label specimen as spinal fluid.
Specimen Stability Information: Refrigerated <48 hours/Ambient < or =48 hours
Performance Information
Day(s) and Time(s) Test Performed
Specimens are processed and reported Monday through Saturday
Analytic Time
1 day
Additional Resources
- Single Antibody Detection of T-Cell Receptor αβ Clonality by Flow Cytometry Rapidly Identifies Mature T-Cell Neoplasms and Monotypic Small CD8-Positive Subsets of Uncertain Significance
- Flow cytometric evaluation of TRBC1 expression in tissue specimens and body fluids is a novel and specific method for assessment of T-cell clonality and diagnosis of T-cell neoplasms
- T-cell clones of uncertain significance are highly prevalent and show close resemblance to T-cell large granular lymphocytic leukemia. Implications for laboratory diagnostics
