Diagnostic utility of the lymphoid screening tube supplemented with TRBC1 for the assessment of T‐cell clonality

Abstract

AbstractIntroductionFlow cytometric panels for the investigation of lymphoproliferative disorders, such as the EuroFlow Lymphoid Screening Tube (LST), often fail to demonstrate T‐cell clonality, as a suitable clonality marker was unavailable until recently. Aim of this study was to evaluate the added value of supplementing TRBC1, a flow cytometric T‐cell clonality marker, to the LST.MethodsFlow cytometric analysis was performed on 830 routine samples referred to our lab for suspicion of hematological malignancy. T‐cells with monotypic TRBC1‐expression were additionally characterized with a 12‐color T‐cell tube and molecular T‐cell receptor gamma gene rearrangement (TRG).ResultsLST analysis revealed 97 (11.7%) samples with the presence of a monotypic T‐cell population according to TRBC1, including 21 (2.5%) “high‐count” (≥500 cells/μL blood or ≥15% of lymphocytes) and 76 (9.2%) “low‐count” (<500 cells/μL blood or <15% of lymphocytes) populations. Clinical symptoms indicative for T‐CLPD could be correlated to 11/21 “high‐count” and 17/76 “low‐count” monotypic T‐cell populations. Molecular TRG analysis demonstrated a monoclonal result in 76% (16/21) of “high‐count” samples and in 64% (42/66; 10 samples not tested) of “low‐count” samples, but also in 9/20 samples with polytypic TRBC1 results.ConclusionAnalysis of an LST tube supplemented with TRBC1 led to the detection of a high number of monotypic T‐cell populations. The detection of numerous small monotypic T‐cell populations raises the question of their clinical significance. A possible flowchart for assessment of these populations, based on the available literature, is proposed. Molecular TRG analysis is complementary and cannot be omitted from T‐cell clonality assessment.