MRD assessment in blood and bone marrow. (A-B) MRD was measured by flow cytometry in peripheral blood (PB) and bone marrow (BM). One patient who had undetectable PB MRD at 4 years was plotted at the lowest margin of detection (10⁻⁶). Patients were stratified by IGHV subgroups: M for mutated, U for unmutated. Red lines indicate median, boxes indicate interquartile ranges. *P < .05; **P < .01; n.s., not significant. (C-E) PB and BM MRD in matched samples at 24, 36, and 48 months. (F) Correlation between PB and BM MRD measurements.