Non-invasive prenatal testing (NIPT) is performed on cell-free fetal DNA that is present in maternal blood during pregnancy. Latest Next-Generation techniques allow a reliable detection of the most common chromosomal aberrations (specifically for the chromosomes 21, 18, 13, X and Y). NIPT may minimize the need for invasive prenatal testing. Positive NIPT results, however, should always be confirmed by amniocentesis or karyotyping.
All testing methods require a sufficient high fraction of fetal DNA which increases during pregnancy and should not be below 2.7% of the total cell-free DNA. Despite this low detection limit, it is currently recommended to perform the test after the 10th week of gestation.
All commercial NIPTs have been validated in high risk cohorts (e.g. women with increased maternal age, abnormal first-trimester screening results). Due to the significantly lower false-positive rate (0.2% in NIPT vs. 5% in first trimester screening [FTS]), the positive predictive value for trisomy 21 accounts for 45% in NIPT compared to approxroximately 4% in FTS.
Despite high sensitivity and specificity, false-positive and false-negative results may occur. This is why the test result describes a risk value rather than a diagnosis.
Prenatalis® NIPT requires a simple blood sample from the expectant woman (10 ml). The test is applicable for single and twin pregnancies. The turn-around time of Prenatalis® is 3-5 working days. The test is conducted and analyzed completely under medical supervision in the Center for Human Genetics and Laboratory Diagnostics, Martinsried (Germany).