Real-time quantitative PCR analysis in case 449. The x-axis presents the time during the course of the disease. The patient relapsed at day 760. The y-axis shows percent MRD level at different time points. Circles indicate the IgH-V_H4 original clone, and this initial clone was undetectable from day 30 to relapse. The IgH-V_H3 relapse clone is shown by triangles. This clone existed as a minor clone at presentation, persisted at detectable levels until day 180, and was detectable from day 600 to relapse. The limit of detection of the assay is represented by a dotted line.