Novel Approaches to Develop Critical Reference Materials for Noninvasive Prenatal Testing: A Pilot Study

Background: Highly characterized reference materials are required to expand noninvasive prenatal testing (NIPT) for low incidence aneuploidies and microdeletions. The goal of this study was to develop reference materials for the development of next generation circulating cell-free DNA (ccfDNA) assays. Methods: This was a prospective study of pregnancies complicated by positive prenatal genetic screening. ccfDNA was isolated from maternal plasma and amplified. Lymphoblastoid cell lines were prepared from maternal peripheral blood mononuclear cells and fetal cord blood cells. Cells were Epstein-Barr virus immortalized and expanded. Amplified DNA and to a limited extent formulated lymphoblastoid-derived ccfDNA was tested in SNP-based and chromosome counting (CC) based massively parallel sequencing assays. Results: Enrolled cases included fetuses with: T21 (2), T18 (1), T18-XXX (1), XYY (1), microdeletions (1), and euploid (2). Three lymphoblastoid cells lines were prepared. Genomic DNA was extracted from cell lines and fragmented to simulate ccfDNA. ccfDNA isolation yielded about 2000 usable genome equivalents of DNA for each case for amplification. Although the sonicated genomic DNA derived from lymphoblastoid cell lines did not yield results compatible with NIPT assays, when blinded, NIPT platforms correctly identified the amplified ccfDNA isolated from blood in the majority of cases. Conclusions: This study showed that maternal blood samples from pregnancies complicated by common chromosomal abnormalities can be used to generate materials for the development and evaluation of NIPT assays.