Trisomy 21 diagnosis value (%)

Sensitivity

Specificity

PPV

NPV

FPR

Maternal age

25.0

88.0

1.3

99.5

12.0

Maternal age + fetal NT thickness

81.3

88.9

4.5

99.9

11.1

Maternal age + biochemical serum

87.5

96.8

15.1

99.9

3.2

Maternal age + fetal NT thickness +biochemical serum

87.5

97.6

19.2

99.9

2.4