Flow cytometric assessment of TCR-VBETA expression in the evaluation of peripheral blood involvement by mature T-cell leukaemias

Abstract

Background Mature T-cell leukaemias have always been considered difficult and challenging to diagnose by flow cytometry, owing to a paucity of immunophenotyping markers that are sensitive for detection of a clonal T-cell population. Demonstration of the neoplastic nature of T-cell proliferations traditionally has relied on morphological criteria and molecular tests. TCR gamma gene rearrangement studies have been used as the only reliable test to prove clonal T-cell receptor. This notion is changing now. Aim To validate the current commercially available kit IOTest TCR Vβ Repertoire Kit (#IM3497, Beckman Coulter) for routine use in the clinical flow cytometry laboratory. Methods EDTA antigoagulated blood specimens: 10 controls and 10 patients with known or suspected T-cell lymphoproliferative disorders were tested for the expression of 24 TCR Vβ antigens with TCR Vβ Repertoire Kit. All specimens were subjected to four-colour immunophenotyping on FC 500 cytometer. Correlation was performed with TCR gene rearrangement by PCR using Cohen’s Unweighted Kappa score. Results All 13 patients had clonal T-cell population detected by flow cytometry. PCR confirmed T-cell clonality in all 13 cases studied– Kappa score 1. No false positive or negative results were observed in our settings. Conclusion Detection of T-cell clonality is no longer restricted to molecular techniques or research laboratories. It is now possible to prove T-cell clonality by means of flow cytometry, based on abnormal distribution of TCR Vβ antigens. Apart from the very high cost, the assay is easy to perform and interpret, with a turnaround time of approximately 2 hours. This test represents a powerful tool for rapid diagnosis of peripheral T-cell lymphoma before the disease becomes a medical emergency and, in some instances, might eliminate the need for further genetic testing.