EP18.08: The role of ultrasound screening in the identification of false negative NIPT results

Non-invasive prenatal testing (NIPT) represents a significant advancement in identifying fetal chromosomal aneuploidies, analysing cell-free fetal DNA in the maternal plasma. Recently there has been a tendency to consider NIPT as the “gold standard” in prenatal screening, but the rate of false negative (FN) results is not well defined. It has been highlighted that placental mosaicism contributes to a major cause of the false negative non-invasive testing. Presenting our cases the aim of this study was to prove the essential role of ultrasound examination in detecting the FN NIPT results. In a retrospective study between 2013 and 2023 at our tertiary centre, the Department of Obstetrics and Gynecology, University of Debrecen, Hungary we collected those cases in which ultrasound examinations and invasive diagnostic testing were conducted following NIPT. During this 10 years at our clinic 165 cases were identified where a diagnostic test by CVS or amniocentesis was performed either to confirm the positive NIPT result or because of abnormal ultrasound finding after negative non-invasive testing. Out of these there were 3 cases where the NIPT result was negative, but the ultrasound revealed some abnormalities, indicating amniocentesis. The results verified presence of mosaic trisomy 16, partial trisomy 3q and trisomy 18 (Edwards syndrome). In further 3 cases, amniocentesis was performed because the NIPT confirmed male, while the ultrasound suggested female fetuses. The diagnostic test results supported the ultrasound findings in two cases, while in one case, mosaic Klinefelter syndrome was confirmed. Thanks to the ultrasound, in three cases, we managed to prevent the birth of a child suffering from a severe genetic disorder. The diagnostic tests supported in every case the gender described by the ultrasound. Our cases demonstrate the benefit of expert ultrasound in the prevention of diagnostic errors by cell-free DNA-based non-invasive testing.