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Sensitive NIPT screening at low fetal fractions
Originally published April 2017
What is fetal fraction?
Fetal fraction describes the proportion of the total cfDNA that is fetal in origin. The 'fetal' component is actually derived from placental trophoblast (2, 3). Thus, cfDNA analysis (NIPT) for fetal trisomy can be considered a 'liquid biopsy' of the placenta.
Why is fetal fraction important?
All methods of NIPT require a minimum fetal fraction for accurate trisomy screening, commonly estimated at 4% (4). However, high analytical sensitivity can be achieved at lower fetal fractions by using protocols that combine statistical methods based on normalised chromosome values in combination with higher sequencing read counts (5, 6). High read counts (counting more cfDNA molecules) is known to improve analytical sensitivity at lower fetal fractions.
percept NIPT employs these methods to accurately detect trisomy at fetal fractions as low as 2.0-2.5% (VCGS validation data on file).
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