Abstract

Background: SneakPeek^® Early Gender Test (Gateway Genomics) is a qPCR-based assay that utilizes a microvolume of maternal plasma to determine the fetal sex as early as 9 weeks gestation. In this study, we aimed to evaluate the accuracy of SneakPeek Early Gender Test for fetal sex determination in self-collected maternal blood samples.
Methods: Maternal capillary blood samples were self-collected by 18 pregnant women between 10.86 and 36.86 weeks of gestation. Venipuncture samples were collected from another set of pregnant women to allow for comparison of test results with those obtained from self-collected capillary samples. A micro volume of maternal plasma from each of the blood samples was obtained through centrifugation. Then, the circulating cell-free DNA was further isolated from the plasma via a commercial DNA extraction kit (NucleoSpin^® Plasma XS, Macherey-Nagel). Real-time quantitative PCR was next performed to amplify and measure the presence of the targeted Y-chromosome specific multi-copy sequence and autosomal control gene (used to measure the total cell-free DNA) in each sample.
Results: All subjects successfully self-collected maternal capillary blood via fingerstick. Y-chromosome DNA was detected in all self-collected capillary and phlebotomist-collected venous blood samples from male bearing pregnancies. SneakPeek correctly determined fetal sex in all 18 self-collected samples and all 18 phlebotomistcollected samples. The clinical laboratory was blinded to the fetal sex for all samples. Results from genetic testing were confirmed via sonographic evaluation at the end of the study. When compared to venous-derived samples, capillaryderived samples had a sensitivity and specificity of 100% and 100%, respectively. SneakPeek accuracy was 100% for fetal sex identification in both self-collected and phlebotomist-collected samples.
Conclusion: Self-collection of maternal capillary blood is a highly accurate method of fetal sex determination early in pregnancy. Cell-free DNA levels were similar between venous and capillary plasma samples demonstrating that self-collection of capillary blood via finger stick is a viable method of obtaining maternal plasma for noninvasive prenatal testing.

Keywords: Fetal DNA; NIPT; SneakPeek; Early gender test; Pregnancy; Self-collect; Finger stick