Next-generation amplicon TRB locus sequencing can overcome limitations of flow-cytometric Vβ expression analysis and confirms clonality in all T-cell prolymphocytic leukemia cases

T-cell receptor (TCR) beta repertoire analysis can distinguish monoclonal from polyclonal T-cell proliferations and crucially aid in the diagnosis of T-cell malignancies. TCR repertoire can be assessed either by flow cytometry (FCM), or by molecular genetic techniques. We compared the results of parallel analyses of V beta expression by FCM and TRB rearrangements by DNA-based next-generation sequencing (NGS) in 80 diagnostic peripheral blood samples of patients with T-cell prolymphocytic leukemia (T-PLL) for (1) the diagnosis of clonality and (2) the assessment of dominant V beta usage. FCM-based analysis of the surface expression was performed using the IOTest Beta Mark kit. The NGS-based analysis employed the multiplex Biomed-2 VB-JB primers. In all the samples, one or two clonal TRB rearrangements were detected by NGS. Although a dominant V beta domain usage was detected by FCM in only 41/80 (51%) samples, clonality was suspected in all of them. In a total of 12 cases, the FCM missed the clone detected by NGS, despite theoretical coverage by the antibodies, the functionality of the rearrangement, and the expression of TCR alpha beta on the cell surface. Partly overlapping with those cases, FCM discovered predominant V beta usage in the T-PLL population that differed from the one detected by NGS in 10 cases. Overall, the concordant NGS and FCM results were obtained on 61/80 (76%) of samples. We conclude that NGS-based TRB analysis can overcome certain limitations of FCM-based analysis by the identification of both productive and nonproductive rearrangements and by covering the whole V beta spectrum. Currently available FCM analysis of V beta expression lacks this breadth but has advantages, such as parallel immunophenotyping and a more accurate quantification of the V beta usage. (c) 2018 International Society for Advancement of Cytometry