Description of a novel FR1 IgH PCR strategy and its comparison with three other strategies for the detection of clonality in B cell malignancies

PCR amplification of IgH gene V-D-J junctional variability (IgH PCR) is increasingly replacing Southern analysis for the detection of clonal lymphoid populations in cases presenting diagnostic difficulties. In order to determine the most efficient strategy, we have compared three known methods, using consensus primers against the VH FR3 or FR2 (FR256) regions, or a mix of six primers against the FR1 region (FR1f), with a new approach using a consensus primer against FR1 (FR1c), never previously described for diagnostic purposes, on DNA from 89 monoclonal B-cell proliferations (16 ALL, 28 CLL/PLL, 15 myelomas, 30 NHL). We obtained a detection rate of 70% for FR3, 64% for FR1f and 77% and 78% for FR256 and FR1c, respectively. Polyclonal lymphocytes and mature T cell malignancies tested negative for all systems. Differences in the detection rate were related not only to the choice of VH primer but also the JH primer(s) used and the pathological subtype. All strategies led to adequate detection of leukaemic DNA, whereas the detection rate in myeloma varied between strategies from 47 to 80% and that of follicular lymphoma from 13 to 63%. The lowest detection rates were observed in follicular lymphoma and in mature CD5 negative proliferations, reflecting the probable correlation between somatic mutation and PCR false-negativity. The combined use of FR1c and FR256 allowed detection in at least one system of 92% of cases overall and at least 75% in all pathological subtypes, thus providing a simple, reliable and rapid non-radioactive system for the detection of B cell clonality.