ERBB2 and breast cancer: Additional comparison between QASeq and other CNV calling tools including CovCopCan33 and CNVKit34 were performed in one normal PBMC DNA sample (expected ERBB2 ploidy = 2.00), two reference spike-in samples prepared by mixing the normal PBMC DNA sample with ERBB2-positive cell-line (SK-BR-3) DNA (expected ERBB2 ploidy = 2.05 and 2.20), and three clinical cfDNA samples from breast cancer patients with ERBB2 amplification identified by QASeq (Ploidy = 2.17, 2.32 and 2.94).