Participation in the College of American Pathologists Laboratory Accreditation Program Decreases Variability in B-Lymphoblastic Leukemia and Plasma Cell Myeloma Flow Cytometric Minimal Residual Disease Testing: A Follow-up Survey.

Context.—: Minimal residual disease (MRD) testing by flow cytometry is ubiquitous in hematolymphoid neoplasm monitoring, especially B-lymphoblastic leukemia (B-ALL), for which it provides predictive information and guides management. Major heterogeneity was identified in 2014.

CD49f protein expression varies among genetic subgroups of B lymphoblastic leukemia and is distinctly low in KMT2A-rearranged cases.

Background: CD49f (integrin α6) is a useful marker for minimal residual disease (MRD) detection in B lymphoblastic leukemia and has recently been suggested to mediate infiltration of the central nervous system by leukemic B lymphoblasts. However, data regarding expression of CD49f protein in B lymphoblastic leukemia are limited, and whether CD49f protein expression varies among genetic subgroups of B lymphoblastic leukemia is unknown.

Methods: CD49f protein expression was characterized by flow cytometry in a series of 40 cases of B lymphoblastic leukemia, which included the genetic subgroups: KMT2A-rerranged, BCR-ABL1+, ETV6-RUNX1+, hypodiploidy, and hyperdiploidy.

Immunophenotyping of Acute Lymphoblastic Leukemia.

Immunophenotyping by flow cytometry is an important component in the diagnostic evaluation of patients with acute lymphoblastic leukemia. This technique further permits the detection of minimal residual disease after therapy, a robust prognostic factor that may guide individualized treatment. We describe here laboratory methods for both the initial characterization of lymphoblasts at diagnosis, and the detection of rare leukemic lymphoblasts after treatment.

PhenoGraph and viSNE facilitate the identification of abnormal T-cell populations in routine clinical flow cytometric data.

Background: Flow cytometric identification of neoplastic T-cell populations is complicated by the wide range of phenotypic abnormalities in T-cell neoplasia, and the diverse repertoire of reactive T-cell phenotypes. We evaluated whether a recently described clustering algorithm, PhenoGraph, and dimensionality-reduction algorithm, viSNE, might facilitate the identification of abnormal T-cell populations in routine clinical flow cytometric data.

Methods: We applied PhenoGraph and viSNE to peripheral blood mononuclear cells labeled with a single 8-color T/NK-cell antibody combination.

Improved compensation of the fluorochrome AmCyan using cellular controls.

Background: Implementation of polychromatic flow cytometry in the clinical laboratory often requires the use of newer fluorochromes, with which experience may be comparatively limited. In the course of implementing polychromatic flow cytometry in our laboratory, we have observed significant differences in compensation values derived for the violet-excited dye, AmCyan, when cells rather than a commercially available set of polystyrene microparticles (BD CompBeads) are used as compensation controls.

Methods: Compensation values were calculated for AmCyan and several other fluorochromes using the BD CompBeads Set according to the manufacturer's protocol, and using unstained and singly stained lymphocytes as compensation controls.