Regarding the Congruence Between 2 Circulating Tumor DNA Sequencing Assays

To the Editor We read with interest the article by Torga and Pienta. They address a timely and important subject, not just for liquid biopsies but also for other commercial next-generation sequencing offerings, and delve deeper into the need for rigorous analytical validation of assays that are used widely in patient care. Unfortunately, there are some key pieces of information missing to allow the reader to fully understand the data. The authors do not provide the variant type or allele frequencies (AFs) for called variants, which is important given different reporting criteria for different assays. Moreover, Stetson et al showed in a similar comparison much greater concordance for variants called at greater than 1% AFs, but striking variability with AFs of less than 1%. Having this information would allow for a discussion as to the difficulties in interpreting plasma next-generation sequencing with low AF results. The study by Torga and Pienta does succeed in cautioning the reader that not all laboratory-developed tests are created equal, and points to a need for rigorously validated reference materials for all assays to benchmark against in the pursuit of more consistent reporting of these important clinical results.

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