Characterization of blasts in clinical samples containing few blasts.

Characterization (eg, phenotyping) of blasts present at low percentages in clinical samples is often required for decisions regarding the approach to therapy. However, the available methods for cell characterization do not yield reliable data when the target cells are scant, and the existing methods for blast enrichment, such as cell sorting by flow cytometry (FCM), cannot enrich blasts of unknown immunophenotype. Blastretriever is a newly developed density centrifugation reagent for retrieving blasts. We examined the utility of Blastretriever in clinical practice. When normal bone marrow (BM) cells were separated with this reagent, myeloblasts and B-cell precursors were enriched and detected as clusters on the FCM cytogram. Compared with a conventional reagent for mononuclear cell preparation, the Blastretriever reagent markedly enriched leukemic myeloblasts, leukemic lymphoblasts, and blastoid lymphoma cells from 36 test samples (BM cells and peripheral blood). We then applied the Blastretriever reagent to samples from 11 consecutive patients who had been referred to us because they exhibited low percentages of blasts (1 patient had only 0.2% blasts). Characterization was needed but impossible with conventional analyses. Blast enrichment was achieved for all 11 samples, allowing reliable blast characterization by FCM, fluorescence in situ hybridization, and/or G-banding determinations. The revealed blast characteristics were valuable for choosing appropriate therapy for the patients.