#Grand Rounds

Do Women at Increased Risk for Down Syndrome Following Standard Screening Prefer NIPT or Invasive Testing?

BACKGROUND AND PURPOSE:

While NIPS (NIPT) may have perceived benefit of no risk of fetal loss, it is not diagnostic
Invasive testing is diagnostic and current risk of loss is substantially less than previously reported (see ‘Related ObG topics below)
Guidelines recommend women be offered invasive testing following an initial ‘high risk’ standard screen for Down syndrome (trisomy 21)
Cheng et al. (BJOG, 2017) sought to determine whether women who were screen positive (high or intermediate risk) for Down syndrome following standard screening and appropriate counseling would opt for NIPS or invasive testing

Prospective cohort study
Inclusion: Women with high risk (term risk ≥ 1:250) or intermediate risk (term risk between 1:251-1:1200) standard screening results for Down syndrome
Exclusion: Multiple or non-viable pregnancies; fetuses with structural abnormalities or hydrops at the time of screening; already had a private self-financed NIPS
Women at high risk were given the following options
- Diagnostic invasive test/chromosomal microarray
- NIPS to detect trisomies 13, 18 and 21
- Decline further testing
Women at high risk received standardized counseling, including need to confirm positive NIPS results; procedure miscarriage risk was described as 0.1-0.2%
Women with intermediate risk (IR) between 1:251 -1:1200 were offered NIPT as a secondary screening test
Testing options were free and wait time for results were equivalent
The primary outcome was NIPS uptake rate

99.1% of 347 of women with high risk results opted for follow-up testing
216 women (62.2%) chose NIPS
Only factors correlated with women opting for microarray were
- Down syndrome risk between 1:2 to 1:9 compared to those with a risk between 1:10 to 1:250
- Nuchal translucency ≥3.5mm
507 (82.6%) of 614 women with IR risk chose NIPS
- NIPS detected one additional case of trisomy 18 and Trisomy 21, but also missed one case of Trisomy 18 and Trisomy 21

Even when cost is not an issue, 60% of women at high risk for Down syndrome still chose a noninvasive, non-diagnostic, less comprehensive option

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