Comparative Analysis Between the EuroClonality-NGS Approach and the LymphoTrack® Dx Assay for IG/TR Marker Screening in Lymphoid Leukemias: A Campus ALL Study

: Next-generation sequencing (NGS) clonality assessment has the potential to overcome the conventional limitations of PCR-based methods. This study aimed at comparing the performance and concordance of the EuroClonality-NGS approach and the LymphoTrack® Dx assay for immunoglobulin (IG)/T-cell receptor (TR)-marker identification at diagnosis. Across four quality-control rounds, six Italian laboratories analyzed 23 acute lymphoblastic leukemia (ALL) and five chronic lymphocytic leukemia (CLL) cases. Overall, 171 rearrangements were identified; 80.7% were detected by both methods. Among shared targets, the concordance was 89.1%, with a higher agreement for IG (IGH 100%-IGK 92.1%) than for TR loci (TRG 78.9%-TRB 81.8%). Bland-Altman analysis indicated no statistically significant systematic bias between methods [mean bias 1.99% (95% CI: -5.29 to +1.31%)]. The Spearman correlation was ρ = 0.680 (p < 0.001). Discordances (10.9%) rarely yielded suitable sensitive PCR assays for disease monitoring (20%) and were never the sole marker in individual patients. In larger independent cohorts, similar rates of no-marker cases were observed (~4-5% in adults), with higher frequencies in T-ALL and no association with blast percentage (Spearman's ρ = 0.447, p = 0.450 in adults and ρ = 0.700, p = 0.188 in childhood). These findings support the reliability of both methods for diagnostic screening, while highlighting locus-specific variability and the importance of multi-target identification.