Table 1 Assumptions on prenatal screening for trisomy 21

 Number of pregnancies screened [17]

100,000

 Prevalence of T21 [19]

0.26%

 Spontaneous fetal loss rate of T21 [20]

43.0%

 Fetal loss rate after amnio/CVS [21]

0.30%

 Median GA at eFTS (days)

88

 eFTS risk cut-off

1 in 1000 (a)

1 in 50 and 1 in 51–1000 (b)

 eFTS DR [8]

95% (a)

67 and 28% (b)*

 eFTS FPR [8]

11% (a)

1 and 10% (b)*

 cfDNA screening DR [5, 6, 10]

99%

 cfDNA screening FPR [5, 6, 10]

0.1%

 cfDNA screening no-call result of 1st/2nd sample [5, 9]

3.3% /1.2% (c)

0.5%/NA (d)^#

 Sample received at MMS lab to eFTS result issued

3

 Sample received at cfDNA screening lab to cfDNA screening result issued [22,23,24]

10 (c)

4 (d) ⁺

 Positive eFTS, high risk or no-call cfDNA screening to GC

3

 Unit cost of blood sample collection tube for cfDNA screening

$10

 Unit cost of eFTS [17]

$120

 Unit cost of cfDNA screening [ 22, 23]

$400 ^@

 Unit cost of GC

$250 ^{^}

 Unit cost of CVS/amnio [17]

$1786.9