Peer reviewed journal
Aim of the study: Analysis of the contribution of segments of antenatal screening using non-invasive testing of free DNA in maternal plasma (NIPT). Creating a model of contingent NIPT screening using results of combined first trimester screening (FTS).
Material and methods: From total 460 prenatal findings in 2017 – 2019 the contribution of FTS, NIPT and 2nd trimester results to indication of diagnosis of 161 trisomies No. 21 (T21) and 53 trisomies No. 18 (T18) was assessed. The results of 24,052 FTS in the same period were sorted into three contingents: 1) combined risk > 1/100, ultrasound finding or marker atypia (high risk – idicated to invasive procedure), 2) risk 1/100 – 1/500 (intermediate risk indicated to NIPT) and 3) risk 1/501 – 1/2,500 (medium risk indicated to integrated test).
Results: In 161 cases of T21 85% were indicated by FTS results, 7.5% by NIPT, 4.5% by integrated test and 3% by ultrasound. In 53 cases of T18 FTS results indicated 77%, NIPT 6%, integrated test 2% and ultrasound 15% cases. 3.8% those screened got into the high risk contingent, 9.4% into the intermediate contingent and 25% into medium risk contingent. More than 25% from all 460 prenatal findings could not be diagnosed by NIPT.
Conclusion: FTS and ultrasound in 1st and 2nd trimesters followed by invasive procedure at high risk mothers remain the basic tools of prenatal diagnosis even in the age of widespread implementation of standard NIPT. Our results can help plan whole-population contingent NIPT screening.