Diagnostic Use

This test is used to detect the presence of a monoclonal T cell population in a blood or tissue samples.

Note: Although accurate in the majority of cases, molecular data should never be used in isolation to establish a diagnosis. The clinical setting, morphological findings and other ancillary tests should always be used in the final interpretation.

Interpretation

Information on T-Cell Receptor Gene Rearrangement Analysis:

During normal T cell development rearrangement processes occur in the T cell receptor (TCR) gene. The structure of the TCR gene consists of constant (C), joining (J) and variable (V) regions. Variability in structure is generated by a process of rearrangement of the DNA which involves splicing out and recombination of DNA segments. This process results in each T cell having its own specific combination of V and J segments which forms the basis of TCR diversity. Each cell has a characteristic rearrangement pattern which is present in all the progeny, therefore a clonal population consists of cells with the same pattern. The Southern blot technique is the ‘gold-standard’ for distinguishing between monoclonal and polyclonal lymphoproliferative disorders but this technique is time-consuming, requires large amounts of high-quality DNA and is technically difficult. PCR-based assays, which do not have these limitations, may be used instead. Most importantly, the PCR based assay can be used on paraffin-block extracted DNA samples, enabling analysis of histologically relevant samples.

PCR analysis of the TCRgamma gene recombination process may be used to asses T cell clonality as the rearrangement occurs in the majority of T cell neoplasms (irrespective of whether a functional TCRgamma receptor is expressed). Monoclonal TCRgamma rearrangements have been found in up to 90% of T cell neoplasms using the PCR method described below. Note, however, that 10-30% of T-cell malignancies may be missed by this method.