FLOW CYTOMETRY WITH T-CELL RECEPTOR B CHAIN CONSTANT REGION-1 ANTIBODY IS SUPERIOR TO GENE REARRANGEMENT STUDIES AT DIFFERENTIAL INTERPRETATIONS OF T-CELL CLONES IN A POPULATION-BASED STUDY

Document Type

Conference Proceeding

Publication Date

11-24-2024

Publication Title

Int J Lab Hematol

Abstract

Introduction: Polymerase chain reaction (PCR) based T-cell receptor (TCR) gene rearrangement study remains a mainstay of T-cell clonality detection. However, false positive results have been reported in up to 20% of cases in literature. Flow cytometry immunophenotyping with T-cell receptor β chain constant region-1 (TRBC1) antibody offers an alternative measure of T-cell clonality and can assess sizes of clones and extent of phenotypic aberrancies. We hypothesize that flow cytometry with TRBC1 can differentially classify T-cell clones into physiologic clones, T-cell clones of uncertain significance (T-CUS), malignant clones. Methods: From a flow cytometry database at Henry Ford Health, a large healthcare system covering a 4.5 million population, 194 consecutive cases in 2023 with TCBR1 panels were retrieved. Included are following antibodies: TCBR1, CD2, CD3, CD4, CD5, CD7, CD8, CD16, CD25, CD45, CD56, and CD57. T-cell clones were identified by having > 85% of TBCR1+ events or < 15%. Immunophenotypic aberrancies were scored as follows: decrease or increase −1; loss −2. Concurrent TCR gene rearrangements were conducted in 76 cases (39.2%). Electronic medical records were reviewed to assign the cases into three categories: physiologic clones, T-CUS and malignant clones. Results: The median age of the 194 patients was 62 (range: 2–97), male to female ratio 1:1.1. The prevalence of physiologic clones, T-CUS and malignant clones was: 6.6% (5/76 cases), 3.6% (7/194 cases), and 6.2% (12/194 cases). By flow cytometry, T-CUS showed significantly smaller clones (9%±23.6% of total lymphocytes vs. 61%±21.8%; p < 0.001) and less immunophenotypic aberrancies (1±0.53 vs. 3±1.27; p < 0.001) than malignant clones, while molecular studies show 100% positivity in both groups. By taking 30% clone size as a cut-off, flow cytometry studies showed significantly higher specificity than molecular testing (100% vs. 81.25%; p < 0.001) in detecting malignant clones without compromising sensitivity (100% with both tests). Conclusions: A population-based retrospective study suggests T-CUS is less frequent than having been reported in literature while significantly complicating the interpretation of T-cell clones. Superior to molecular testing, flow cytometry with TCBR1 could potentially differentiate T-CUS from overt malignant clones by measuring clone size and extent of immunophenotypic aberrancy. Further studies are warranted to affirm the utility.

Volume

46

Issue

S2

First Page

95

Last Page

96

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