Tricky TRIC: A replication study using trophoblast retrieval and isolation from the cervix to study genetic birth defects.

Objective: Noninvasive Prenatal Diagnosis has recently been introduced for a limited number of monogenetic disorders. However, the majority of DNA diagnostics still require fetal material obtained using an invasive test. Recently, a novel technique, TRIC (Trophoblast Retrieval and Isolation from the Cervix), has been described, which collects fetal trophoblast cells by endocervical sampling. Since this technique has not been successfully replicated by other groups, we aimed to achieve this in the current study.

Method: Pregnant women referred for transvaginal chorionic villous sampling (CVS) were asked for an endocervical sample prior to CVS. The TRIC samples were processed to isolate trophoblast DNA. TRIC DNA was used in ForenSeq to determine the amount of maternal DNA contamination, and for Sanger sequencing in case of a monogenic disorder.

Results: 23%-44% of samples had a sufficiently high fetal DNA fraction to allow genetic testing, as calculated by Sanger sequencing and ForenSeq, respectively.

Conclusion: We have been able to successfully replicate the TRIC protocol, although with a much lower success rate as described by the original study performing TRIC. As we obtained the samples in the actual clinical setting envisioned, the method in its current setup is not advisable for use in prenatal diagnostics.