From Down syndrome screening to noninvasive prenatal testing: 20 years' experience in Taiwan

Down syndrome is the most common autosomal chromosome aneuploidy. The prenatal Down syndrome screening protocol has been known in Taiwan for the past 20 years. The maternal serum double markers required for the screening test was first implemented into the general prenatal check-up back in 1994, where it had around a 60% detection rate at a 5% false positive rate. The first trimester combined test was started in 2005, and the maternal serum quadruple test was introduced in 2008 to replace the previous double test. The overall detection rate for the current screening strategies (first trimester combined or second trimester quadruple test) in Taiwan ranges between 80% and 85% at a fixed 5% false positive rate. Noninvasive prenatal testing (NIPT) is the latest powerful fetal aneuploidy detection method and has become commercially available in Taiwan starting from 2013. The sensitivity and specificity for NIPT are very high (both over 99%) according to large worldwide studies. Our preliminary data for NIPT from 11 medical centers in Taiwan have also shown a 100% detection rate for Down syndrome and Edwards syndrome, respectively. Invasive chromosome studies such as amniocentesis or chorionic villus sampling cannot be replaced by NIPT, and all prenatal screening and NIPT results require confirmation using invasive testing. This review discusses the Down syndrome screening method assessments and the progress of NIPT in Taiwan.