Frequency of relapse. Bar plot showing the frequency of relapse according to MRD status for MRD-negative patients (n = 77, 5 relapses), MRD-positive patients (n = 28, 17 relapses), and MRD-positive patients within the quantitative range of the PCR (n = 15, 13 relapses, being a subset of the MRD-positive group). The 2 patients who did not relapse in the last group were censored at the time of stem cell transplantation.