Figure 1: Comparison of the probability that an observed variant is real [54] for subclonal variants using Q30-filtered reads of an Illumina HiSeq2500 (NGS) versus Duplex Sequencing. Error Frequencies of each approach is given in parenthesis. PPV (Positive Predictive Value)=(Expected Number of true positives)/(Expected Total Number of Positive Calls). Note that the PPV is 0.50 for NGS when the variant frequency at a single position is ~1/100, i.e., any variant call has a 50/50 chance of being real hen the frequency of real variants equals the frequency of mistakes invalidity [62].