Circulating Cell-Free Plasma DNA in Noninvasive Prenatal Paternity Testing with Short Tandem Repeats (STRs)

Paternity relationship can be established using STR markers in a minimally invasive manner during the prenatal period in the early weeks of pregnancy or in advanced pregnancy using circulating cell-free DNA (ccf DNA) drawn from the mother. The aim of our presentation is to demonstrate the advantages of ccf plasma DNA in establishing the paternity of an unborn child. Between mother and the alleged father (AF) of the fetus, an avuncular relationship as uncle-niece exists.

As biological samples, saliva was collected with buccal swabs from the mother and AF. For the fetus, we separated plasma from drawn blood from the mother, and further, we isolated ccf DNA from the mother's plasma sample. The DNA samples were quantified on a 7500 ABI Real-Time PCR using Investigator Quantiplex Pro Kit (Qiagen, Germany). Genotyping of the DNA samples was performed on a ProFlex PCR System (Thermo Scientific, USA) using the multiplex STR markers from Global Filer PCR Amplification Kit (Thermo Scientific, USA). Further, PCR products were run on capillary electrophoresis on an ABI 3500 Genetic Analyzer (Applied Biosystems, USA).

The AF was confirmed as the biological father of the child, with a probability of paternity (PP) = 99.99999% and a cumulative paternity index (CPI) = 8.300 x 103.

In the case of advanced pregnancies from sexual assaults or incestuous relationships, the use of ccf DNA to establish the genetic profile of the fetus represents an advantage for establishing the paternity relationship between the fetus and AF. The method proves its efficiency as it has the advantage of speed of probation through forensic genetic expertise.