Longitudinal follow-up of PB MRD, showing proportions of patients in each MRD category, by treatment arm. (A) FC-obinutuzumab plus I arm. (B) I arm. PB MRD was assessed every 6 months from month 16. For each treatment arm, we defined 2 groups with MRD: the first included cases with MRD ≥0.01% and was referred to as positive MRD; and the second included cases with positive MRD <0.01% and was referred to as low-level positive MRD. When the positivity criteria were not met, the MRD status was undetectable and a limit of sensitivity of the test was calculated. Undetectable MRD cases were then subcategorized into 3 groups depending on the limit of sensitivity: MRD4 comprised sensitivity 10−4 to 10−5, MRD5 comprised sensitivity 10−5 to 10−6, and MRD6 comprised sensitivity below 10−6. As we were able to produce high-sensitivity tests, the proportion of cases with MRD4 was low and the proportions with MRD5 and MRD6 were well balanced.