A Comparative Study of Polymerase Chain Reaction Detection of Clonal T-cell Receptor Gamma Chain Gene Rearrangements Using Polyacrylamide Gel Electrophoresis versus Fluorescence Capillary Electrophoresis

Abstract

Polymerase chain reaction (PCR)-based molecular techniques are useful adjunctive tools in the diagnosis of cutaneous T-cell lymphomas (CTCL). This study compares the sensitivity of PCR analysis of the T-cell receptor-gamma (TCR-gamma) gene rearrangements using conventional polyacrylamide gel electrophoresis (PCR-PAGE) and fluorescent capillary electrophoresis (PCR-FCE). A total of 22 paraffin blocks were analysed using PCR-PAGE and PCR-FCE. There were 17 cases of mycosis fungoides (MF), 4 cases of non-MF CTCL and 1 case of lymphoblastic leukaemia. Complete agreement was obtained between PCR-PAGE and PCR-FCE in 19 of the 22 cases, giving a concordance rate of 86.4%. PCR-FCE had a higher sensitivity of 77.3%, compared to 63.6% for PCR-PAGE, allowing the detection of 3 additional cases of clonal T-cell rearrangements, which had equivocal or polyclonal bands on PAGE. Two of these 3 cases were in erythrodermic MF patients. PCR-FCE also allowed the detection of matching clones in serial specimens taken from different sites and at different time intervals in patients with MF. However, matching clones from different specimens can be achieved qualitatively in PCR-PAGE by running and comparing these on the same polyacrylamide gel block. Both PCR-PAGE and PCR-FCE are useful in detecting T-cell clones in CTCL, with both methods being comparable in sensitivity and showing a high concordance rate of 86.4%. PCR-FCE has the added advantage of exhibiting semiquantitative properties, which may be important in early or erythrodermic MF cases, but the requirement for sophisticated and costly machinery limits its availability to high-capacity laboratories. The well-established PCR-PAGE method is a suitable alternative in routine clinical applications.