Clinical Application of Easychip 8x15K Platform in 4106 Pregnancies Without Ultrasound Anomalies

Abstract

Clinical utility of Array-CGH Easychip 8x15K platform can be assessed by testing its ability to detect the occurrence of pathogenic copy number variants (CNVs), and occurrence of variants of uncertain significance (VoUS) in pregnancies without structural fetal malformations. The demand of chromosomal microarray analysis in prenatal diagnosis is progressively increasing in uneventful pregnancies. However, depending on such platform resolution, a genome-wide approach also provides a high risk of detecting VoUS and incidental finding (IF) also defined as "toxic findings." In this context, novel alternative strategies in probe design and data filtering are required to balance the detection of disease causing CNVs and the occurrence of unwanted findings. In a cohort of consecutive pregnancies without ultrasound anomalies, a total of 4106 DNA samples from cultured and uncultured amniotic fluid or chorionic villi were collected and analyzed by a previously designed Array-CGH mixed-resolution custom platform, which is able to detect pathogenic CNVs and structural imbalanced rearrangements limiting the identification of VoUS and IF. Pathogenic CNVs were identified in 88 samples (2.1%), 19 of which (0.5%) were undetectable by standard karyotype. VoUS accounted for 0.6% of cases. Our data confirm that a mixed-resolution and targeted array CGH platform, as Easychip 8x15K, yields a similar detection rate of higher resolution CMA platforms and reduces the occurrence of "toxic findings," hence making it eligible for a first-tier genetic test in pregnancies without ultrasound anomalies.

Keywords: Array CGH; CNV; General cytogenetics; Genetic counseling; Pregnancy without ultrasound anomalies; VOUS.