Dried blood spot sampling for detection of monoclonal immunoglobulin gene rearrangement.

Molecular methods are important tools for diagnosis and monitoring of many lymphoproliferative disorders. The reliability of lymphoma diagnoses is strikingly different between developed and developing countries, partly due to lack of access to these advanced molecular analyses. To overcome these problems, we propose a new application of dried blood spots (DBS) for detecting clonal B-cell populations in peripheral blood (PB). We ensured that the DBS contained sufficient lymphocytes to perform a PCR-based clonality assay without producing false positives. Using the Namalwa B-cell line, we established that the assay is sensitive enough to detect 200 clonal cells in the analyzed sample. Very similar clonal results were obtained between DNA from DBS and fresh whole blood from patients with B-cell chronic lymphocytic leukemia. B-cell clonality can also be detected in DBS from African children with EBV-associated diseases. This is the first study demonstrating that clonality testing can be performed on DBS samples, thus improving the diagnostic and monitoring options for lymphoproliferative diseases in resource-limited settings.