Test ID: LCMS
Leukemia/Lymphoma Immunophenotyping by Flow Cytometry

A request for leukemia immunophenotyping initiates a process in the laboratory to determine the most appropriate and cost-efficient immunophenotyping antibody panel. A screening panel is initially performed to evaluate for B-cell clonality by kappa and lambda light chain expression, increased percentage of blasts or plasma cells by CD45 expression, and side scatter gating. This panel also includes antibodies to assess the percentage of CD3-positive T-cells and CD16-positive/CD3-negative natural killer (NK) cells present. This panel also determines if there is an increased percentage of T-cells that aberrantly coexpress CD16, an immunophenotypic feature of T-cell granular lymphocytic leukemia. 

This limited panel, together with the provided clinical history and morphologic review, is used to determine what, if any, further testing is needed for disease diagnosis or classification. If additional testing is required, it will be added per algorithm to fully characterize a disease state with a charge per unique antibody tested.

If an increased percentage of leukemic blasts are identified by immunophenotyping or if morphologic evaluation suggests that flow cytometry is needed for leukemia diagnosis and classification, then an acute leukemia immunophenotyping panel will be ordered. A myeloid linage-specific panel will be used in follow-up specimens for previously phenotyped acute myeloid leukemias and in cases in which morphologic review or flow triage analysis suggests an increase in myeloid lineage blasts, yet these cells either comprise <20% of the total specimens cellularity or the specimens is sparsely cellular and therefore optimum utilization is required. If excess kappa- or lambda-positive lymphocytes are identified in the screening panel, then a B-lymphocyte immunophenotyping panel will be ordered. If there are increased numbers of T or NK cells, or if a CD3-positive T-cell population that coexpresses CD16 is identified, a T-lymphocyte immunophenotyping antibody panel will be performed. In our laboratory, T-cell immunophenotyping studies typically include CD2, CD3, CD5, CD7, CD4, and CD8. Additional antibody panels may be used in the evaluation of potential T- and NK-cell lymphoproliferative disorders, these include: KIR panel to assess for the expression of additional NK-cell-associated antigens (useful in establishing a diagnosis of granular lymphocytic leukemia); TCR V Beta panel to assess the expression of T-cell receptor beta chain variable region family expression (useful in establishing T-cell clonality). If an increased population of plasma cells is noted a plasma cell screen for monoclonality will be performed.

If no abnormalities are detected by the triage panel, no further flow cytometric assessment will be performed unless otherwise indicated by specific features of the clinical presentation or prior laboratory results. If necessary, cytochemical stains will be performed at no additional charge to further subclassify the disease process. In some instances, additional cytogenetic or molecular genetic studies may be indicated by the immunophenotyping results. In these cases, the ordering physician will be contacted prior to these studies being performed.

Immunophenotyping is performed by multicolor flow cytometry using monoclonal antibodies directly conjugated with different fluorochromes. (Borowitz M, Bauer KD, Duque RE, et al: Clinical applications of flow cytometry: immunophenotyping of leukemic cells; Approved Guideline: 1997. NCCLS document H43-A. NCCLS, Wayne, PA; Borowitz MJ, Guenther KL, Shults KE, et al: Immunophenotyping of acute leukemia by flow cytometric analysis. Use of CD45 and right-angle light scatter to gate on leukemic blasts in three-color analysis. Am J Clin Pathol 1993;100:534-540; van Den Beemd R, Boor PP, van Lochem EG, et al: Flow cytometric analysis of the Vbeta repertoire in healthy controls. Cytometry 2000 August 1;40[4]:336-345)

Specimens are processed Monday through Sunday and reported Monday through Friday.