Single-nucleotide polymorphism leading to false allelic fraction by droplet digital PCR

Eric S. Christenson, W. Brian Dalton, David Chu, Ian Waters, Karen Cravero, Daniel J. Zabransky, Amy E. DeZern, Ben Ho Park

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


BACKGROUND: Molecular-based diagnostics have great utility for cancer detection. We have used droplet digital PCR (ddPCR) as a platform for identifying mutations in circulating plasma tumor DNA (ptDNA). We present the unexpected finding of a spurious mutant allele fraction that was discovered to be artifactual because of the presence of a single-nucleotide polymorphism (SNP) in a patient sample. DESIGN AND METHODS: Probe and primer combinations for the K700 and V701 loci of the SF3B1 spliceosome gene were designed for ddPCR to identify the percentage of mutant and wild-type alleles. Clinical samples from patients with cancer with known SF3B1 mutations were collected and tested to evaluate the assays' ability to detect SF3B1 mutations in ptDNA. RESULTS: Patient samples showed SF3B1 K700E mutations within the ptDNA of 4 patients with acute leukemia and 3 with myelodysplastic syndrome who were known to harbor this mutation. A blood sample from a patient with lung cancer with a known SF3B1 V701F mutation was also analyzed and this mutation was successfully identified in ptDNA. However, 1 of the patients with a K700E mutation was found to have a mutational burden of 98%. After careful analysis of this locus by Sanger sequencing and ddPCR, this patient was found to have an SNP (R702R), which prevented binding of the ddPCR wild-type probe to its cognate allele. CONCLUSIONS: These results further support that ddPCRbased assays may be valuable companion diagnostics for the identification and monitoring of patients with cancer, but the results also emphasize the need to identify SNPs at loci that are being analyzed.

Original languageEnglish (US)
Pages (from-to)1370-1376
Number of pages7
JournalClinical chemistry
Issue number8
StatePublished - Aug 2017

ASJC Scopus subject areas

  • General Medicine


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