CD38 expression on chronic lymphocytic leukaemia (CLL) cells is a poor prognostic factor, however, methods for measuring this vary. The QuantiBRITE™ flow cytometry (FC) system yields an absolute antigen expression value (antibodies bound/cell, ABC) and may be useful in standardizing CD38 expression analysis. We evaluated cryopreserved pretreatment CLL cells for CD20 ABC, CD38 ABC, and percentage of CD38+ B cells from 131 patients requiring therapy. The 92 patients (70%) with ≥ 100 CD38 ABC had worse overall survival (OS; 34% at 5 years) compared with those with <100 CD38 ABC (70% at 5 years, mortality hazard ratio 2.30, 95% confidence interval 1.28-4.12; two-tailed P = 0.003). Among the 64 patients with <30% CD38+ cells. OS of the 25 with ≥ 100 ABC was worse than that of the 39 with < 100 ABC (P = 0.018). OS of patients with < 30% CD38+ cells and ≥ 100 ABC was actually similar to that of patients with ≥ 30% CD38+ cells. BrightCD20 expression (≥ 20 000 ABC) was not associated with a worse as (P = 0.10). The presence of ≥ 100 CD38 ABC in CLL patients requiring therapy is an unfavourable prognostic factor for as and quantitative FC may be superior to percentage CD38+ cell assessment. Prospective trials are required to determine more precisely the prognostic significance of absolute expression levels in fresh CLL cells.
- Flow cytometry
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