Professional
Technical
In the Industry Vocabulary Test
allelic fraction
The proportion of sequencing reads containing a variant allele at a specific genomic position in tumor tissue.
Full Definition
Allelic fraction represents the ratio of variant-containing reads to total reads at a genomic locus, expressed as a percentage or decimal. In oncology informatics, this metric helps determine variant confidence levels and tumor cellularity. Editorial teams must distinguish this from allele frequency, which refers to population-level variant prevalence. The term is critical in molecular pathology reports and variant calling pipelines.
Usage
Usage note: Always lowercase when used as a common noun; capitalize when part of a formal measurement name.
In Context
- "The pathologist reported an allelic fraction of 0.23 for the EGFR mutation, indicating moderate tumor cellularity." — Molecular pathology report
- "Quality control protocols require a minimum allelic fraction threshold of 5% for variant reporting." — Laboratory standard operating procedure
Also known as
variant allele fraction
VAF
Don't confuse with
allele frequency
mutant allele frequency