(a) Heatmaps show the detection of known variants (rows) in ctDNA assay replicates (columns). Variants are sorted by expected variant allele frequency (VAF) in descending order for each sample/input quantity (Lbx-high 25ng, Lbx-low 10–50ng), and replicates are arranged hierarchically by assay type, test lab and replicate number. Grey rows indicate where known variant was not within the target regions for a given assay. (b,c) Curves showing the relationship between cell-free DNA input quantity (Lbx-low) and variant detection sensitivity (b) and pairwise reproducibility (c). (d) Bar charts show pairwise reproducibility scores for participating assays (n = 132 for ROC, ILM TFS; n = 56 for BRP; median ± range). Reproducibility is reported separately for all pairwise comparisons in Lbx-high and Lbx-low and separately for all within-lab and between-lab comparisons. Note that the IDT hybrid-capture assay is not included in these comparisons because this panel had limited overlap with TFS amplicon target regions.