Table 1 Screening of Down syndrome in foetuses using four serological screening methods and NIPS.

From: Clinical strategy study on prenatal screening and diagnostic model for Down syndrome

Screening method

Biochemical screening in the first trimester

Combined first trimester screening

Double screening in the second trimester

Triple screening in the second trimester

NIPS

Screening number

19,591

19,723

52,321

15,804

19,296

true positive(a)

15

15

37

16

46

false positive(b)

1041

446

2838

485

14

false negative(c)

7

7

15

5

1

true negative(d)

18,528

19,255

49,431

15,298

19,235

DR(%)

68.18

68.18

71.15

76.19

97.87

FPR(%)

5.31

2.26

5.42

3.07

0.07

PPV(%)

1.42

3.25

1.29

3.19

76.67

  1. DR: detection rate, the ratio of the number of cases with positive screening results and confirmed diagnosis to the number of cases with positive “gold standard” test results, DR = a/(a + c); FPR: False positive rate, refers to the ratio of the number of cases with positive screening results but negative “gold standard” test results, FPR = b/(b + d); PPV: Positive predictive value, refers to the ratio of the “gold standard” test result being positive to the total number of positive cases detected through screening, PPV = a/(a + b).
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