Table 2 Impact of within-day and between day variations on assessment of biochemical and combined risk for Down syndrome

High risk *

Mean ± SD

1.87 ± 0.08

0,29 ± 0,01

52.6 ± 6.2

154.4 ± 16.1

CV† (%)

4.27

3.45

11.72

10.45

Medium risk **

Mean ± SD

0.59 ± 0,03

0,29 ± 0,01

732.6 ± 76.0

699.9 ± 77.2

CV† (%)

5.08

3.45

10.37

11.03

Low risk ***

Mean ± SD

1.87 ± 0.08

1.26 ± 0.05

3060.8 ± 323.5

2527.7 ± 328.3

CV† (%)

4.27

3.97

10.57

12.98

Human serum

Mean ± SD

1.47 ± 0.07

1.79 ± 0.06

8668.2 ± 819.4

7313.9 ± 900.9

CV† (%)

4.76

3.35

9.45

12.32

Between-day variations of calculated risk

High risk *

Mean ± SD

1.70 ± 0.09

0.27 ± 0.01

45.39 ± 5.5

145.6 ± 18.2

CV† (%)

5.26

3.43

12.12

12.50

Medium ris k **

Mean ± SD

0.59 ± 0.03

0.27 ± 0.01

661.4 ± 68.7

646.1 ± 68.58

CV† (%)

4.3

3.43

10.39

11.54

Low risk ***

Mean ± SD

1.70 ± 0.09

1.26 ± 0.05

2442.6 ± 304.6

1993.3 ± 219.7

CV† (%)

5.26

4.28

12.47

11.02

Human serum

Mean ± SD

1.36 ± 0.08

1.76 ± 0.09

7446.5 ± 796.8

6146.4 ± 785.4

CV† (%)

6.17

5.20

10.70

12.77