2018 Articles

Validation of a SNP-based non-invasive prenatal test to detect the fetal 22q11.2 deletion in maternal plasma samples

Ravi, Harini; McNeill, Gabriel; Goel, Shruti; Meltzer, Steven D.; Hunkapiller, Nathan; Ryan, Allison; Levy, Brynn; Demko, Zachary P.

Introduction
Non-invasive prenatal testing (NIPT) for aneuploidy using cell-free DNA in maternal plasma has been widely adopted. Recently, NIPT coverage has expanded to detect subchromosomal abnormalities including the 22q11.2 deletion. Validation of a SNP-based NIPT for detection of 22q11.2 deletions demonstrating a high sensitivity (97.8%) and specificity (99.75%) has been reported. We sought to further demonstrate the performance of a revised version of the test in a larger set of pregnancy plasma samples.

Methods
Blood samples from pregnant women (10 with 22q11.2-deletion‒affected fetuses and 390 negative controls) were successfully analyzed using a revised SNP-based NIPT for the 22q11.2 deletion. The sensitivity and specificity of the assay were measured.

Results
Sensitivity of the assay was 90% (9/10), and specificity of the assay was 99.74% (389/390), with a corresponding false positive-rate of 0.26%.

Discussion
The data presented in this study add to the growing body of evidence demonstrating the ability of the SNP-based NIPT to detect 22q11.2 deletions with high sensitivity and specificity.