Comparison of MRD results assessed with different techniques. (A) MFC vs IG/TR RT-qPCR.¹¹  The sensitivity of MFC for MRD detection relative to RT-qPCR (y-axis) is shown for certain time points (days 15, 33, and 78) and for all samples together. Data are presented for variable numbers of acquired cells (x-axis): all samples (independent of cell counts; n = 377) and samples with at least 1 (n = 330), 2 (n = 287), 3 (n = 255), 4 (n = 227) and 5 (n = 191) million cells acquired. Sensitivity is calculated as the number of samples positive by both FCM and PCR divided by the total number of samples positive by PCR. The sensitivity significantly increases when larger numbers of cells are acquired. (B) Immunoglobulin heavy chain RT-qPCR vs immunoglobulin heavy chain NGS.⁷  The comparison of MRD as detected by RT-qPCR and NGS is shown for different follow-up time points (days 15, 33, and 78) by qPCR (x-axis) and NGS (y-axis). The correlation of both methods is good (R² = 0.72) with the majority of the noncorrelating samples below the sensitivity thresholds of the methods. (C) IG/TR RT-qPCR vs BCR-ABL1 RT-qPCR.¹⁷  Comparison of MRD levels in ALL patients as detected by IG/TR RT-qPCR (x-axis) vs BCR-ABL1 genomic transcript quantification (y-axis). A significant number of samples (23%) have quantifiable BCR-ABL1 levels, whereas IG/TR MRD is negative. Panel C adapted from Hovorkova et al.¹⁷