Fig. 3

SCAN-SNV FDR tuning strategy. Somatic SNVs and hSNPs are supported by 50% of DNA prior to amplification in single cells. The shapes of VAF distributions for the two mutation types should be similar because both are equally affected by allelic imbalance, but artifacts in the candidate sSNV set (red line) usually create an enrichment at low VAF compared with hSNPs (black line). VAFs for the unknown number of true mutation among candidate sSNVs (green area) should be distributed similarly to hSNPs. Potential values for the total number of true sSNVs N (dashed lines) can be evaluated by first distributing the N mutations according to the hSNP VAFs and then ensuring the predicted numbers of sSNVs at each VAF do not exceed the number of candidates at that VAF. The largest such N provides an upper bound on the number of somatic mutations. Given N, a lower bound on the fraction of artifacts amongst sSNVs at any VAF can be estimated