UCSF

What's Already Known about This Topic? Aneuploidy screening using cell free DNA (cfDNA) has recently been expanded to include selected microdeletions. However, validation has been limited, and the real-world positive-predictive value is unknown. What Does This Study Add? Here we describe three cases of false positive cfDNA microdeletions because of small, non-pathogenic copy number variants near the region of interest. These findings elucidate one mechanism of false-positive results with this screening test and suggest that additional validation is necessary before wider use in clinical practice.