Noninvasive prenatal detection of trisomy: a review of methods and comparison of approaches

Non-invasive prenatal testing (NIPT) of trisomy has recently become widespread in clinical practice in many countries, including Russia. Despite the fact that NIPT does not allow to estimate the number and structure of all chromosomes of the fetus (this is possible only when using karyotyping), this analysis has good sensitivity and specificity indicators, and also allows eliminating the risks accompanying invasive diagnostic procedures (amniocentesis, cordocentesis, chorionic villus biopsy, etc.). The sequences of cell-free fetal DNA (cffDNA), which are present in low concentrations in the blood of a pregnant woman and disappear after pregnancy, are mainly used for NIPT. Currently NIPT uses Next Generation Sequencing methods (NGS). The review presents main approaches and methods used for non-invasive prenatal testing of trisomy: massive parallel sequencing by the shotgun method (MPSS), targeted parallel sequencing (t-MPS) and approaches based on the study of single nucleotide polymorphisms (SNP). In review we also compare efficacy of their use for the detection of trisomy of chromosomes 13, 18 and 21 (Patau syndrome, Edwards syndrome and Down syndrome, respectively). When using MPSS, sequences of the whole genome are analyzed, and with t-MPS, only specific sequences of interest are analyzed. The article also discusses methods for analyzing mRNA, fetal epigenetic markers, and additional signal amplification methods (for example, DANSR, Digital Analysis of Selected Regions). The review presents the main reasons for the appearance of false (false positive and false negative) results in NIPT (mosaicism, the phenomenon of “twin resorption”, low levels of fetal DNA, etc.). A brief description of the current place of NIPT in clinical practice and prospects for the inclusion of NIPT in the prenatal screening scheme, as well as the main difficulties that limit the wider use of NIPT technology in the clinic, are given. Primarily, these difficulties are associated with the specificity of cell-free fetal DNA (concentration, individual differences, etc.), as well as ethical issues (genetic determinism, informed patient consent, etc.).

трисомии, неинвазивное пренатальное тестирование, НИПТ, внеклеточная фетальная ДНК, trisomy, non-invasive prenatal testing, NIPT, extracellular fetal DNA