Correlation heatmap of all replicate UHRR pairs. Heatmap of Pearson correlations between replicate pairs of UHRR samples highlights the inter-experiment, inter-run, and inter-chip differences; particularly at the inter-experiment level. Red cells correspond to ~80% correlation and white to 100% correlation. Batches and sample numbers are consistent with the colouring and labelling in Figures 1 and Additional File 2. A: detection filtered (DF); B: DF & quantile normalised (QN); C: DF & QN &ComBat(by experiment); D: DF & QN &ComBat(by run).