Second tier non-invasive prenatal testing in a regional prenatal diagnosis service unit: a retrospective analysis and literature review

Abstract

The Hong Kong Hospital Authority has newly introduced a new Down's syndrome screening algorithm that offers free-of-charge noninvasive prenatal testing (NIPT) to women who screen as high risk. In preparation for this publicfunded second tier NIPT service, the present study was conducted to retrospectively analyse women eligible for NIPT and to review the local literature. Methods: Our retrospective study included women screened as high risk for Down's syndrome (adjusted term risk ≥1:250) during the period of 1 January 2015 to 31 December 2016. We performed descriptive statistics and multivariable logistic regression to examine the factors associated with women's choice between NIPT and invasive testing. We also reviewed existing local literature about second tier NIPT. Results: The study included 525 women who screened positive: 67% chose NIPT; 31% chose invasive diagnostic tests; and 2% declined further testing. Our literature review showed that in nonresearch (self-financed NIPT) settings, NIPT uptake rates have been increasing since 2011. Nulliparity, first trimester status, higher education,

The Emergence and Global Spread of Noninvasive Prenatal Testing

“…Local research confirmed pregnant people's preference for NIPT (173). The uptake rate among users with a high-chance first-tier screening result gradually increased, ranging from 20% to 90% (108). Both women and healthcare providers perceived NIPT as beneficial in improving prenatal care.…”

“…They would accept a miscarriage risk of up to 0.5% as a trade-off for obtaining more rather than less information when making a reproductive decision (33). Interestingly, women expressed a decreased interest in NIPT and an increased preference for invasive testing (with a chromosomal microarray for obtaining more definitive genetic results) when they were counseled that the procedure-related fetal loss rate of the invasive test was 0.1-0.2% (34,108).…”

Second-tier non-invasive prenatal screening for Down syndrome in a public obstetric unit: the first 12 months

“…In 2014, when NIPT remained a self-financed item, 57.8% of women opted for NIPT as a second-tier test after screen positive, compared with 30.4% opting for NIPT as a primary screening test 14 . In 2015-2016, the uptake of NIPT in women with positive DS screening increased to 67%, whereas 31% opted for invasive testing and 2% had no further testing 11 . In 2015-2016, when NIPT was offered free-of-charge under a university research protocol, among 347 women with positive DS screening, 62.2% opted for NIPT and 37% opted for invasive testing with chromosomal microarray 15 .…”

“…For invasive testing, quantitative fluorescent polymerase chain reaction (to exclude common aneuploidies) was used, followed by chromosomal microarray and/or karyotyping. The procedure-related miscarriage risk for chorionic villus sampling was 1% and for amniocentesis was 0.1% to 0.5% 6,11,12 . All screen-positive women were offered a detailed morphology scan at 20 weeks to exclude fetal structural abnormalities unless the NIPT or invasive testing already confirmed specific pathology.…”

“…In 2011, NIPT was first available in Hong Kong as a self-financed examination 11 . In the last quarter of 2019, NIPT was implemented in all public obstetric units as a formal second-tier test for women with positive conventional DS screening, with an objective to reduce the need for invasive testing rather than to boaster the detection rate for DS.…”