Quantitative Real-Time PCR Method for Detection of B-Lymphocyte Monoclonality by Comparison of κ and λ Immunoglobulin Light Chain Expression

Abstract

Background: An abnormal IgLκ:IgLλ ratio has long been used as a clinical criterion for non-Hodgkin B-cell lymphomas. As a first step toward a quantitative real-time PCR-based multimarker diagnostic analysis of lymphomas, we have developed a method for determination of IgLκ:IgLλ ratio in clinical samples. Methods: Light-up probe-based real-time PCR was used to quantify IgLκ and IgLλ cDNA from 32 clinical samples. The samples were also investigated by routine immunohistochemical analysis and flow cytometry. Results: Of 32 suspected non-Hodgkin lymphoma samples analyzed, 28 were correctly assigned from real-time PCR measurements assuming invariant PCR efficiencies in the biological samples. Four samples were false negatives. One was a T-cell lymphoma, one was a diffuse large B-cell lymphoma, and one was reanalyzed and found lymphoma-positive by in situ calibration, which takes into account sample-specific PCR inhibition. Twelve of the samples were fine-needle aspirates, and these were all correctly assigned. Conclusions: This work is a first step toward analyzing clinical samples by quantitative light-up probe-based real-time PCR. Quantitative real-time PCR appears suitable for high-throughput testing of cancers by measuring expression of tumor markers in fine-needle aspirates.