# Table 2 Calculation of the neutralizing antibody titer determined with NT-PCR assay (1.) and its intra- and inter-assay variability (2.)

1. Calculation of the NT-PCR assay

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Î£ R2single well*

antibody dilution

assay #

1a

2a

3a

4a

5a

6b

7c

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1:40

0.0250

Â

0.25

0.31

0.27

0.33

0.22

0.32

0.31

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1:80

0.0125

Â

1.34

1.37

1.31

1.37

1.26

1.35

1.42

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1:160

0.0063

Â

1.44

1.36

1.28

1.27

1.30

1.23

0.71

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1:320

0.0031

Â

1.61

1.52

1.45

1.49

1.17

1.44

1.11

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1:640

0.0016

Â

1.20

1.77

1.65

1.73

1.41

1.65

1.43

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1:1280

0.0008

Â

1.23

1.34

1.30

1.54

1.30

1.41

1.06

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1:2560

0.0004

Â

1.24

1.36

1.39

1.38

1.31

1.46

1.26

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1:5120

0.0002

Â

0.25

0.31

0.27

0.33

0.22

0.32

0.31

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2. Inter-and intra-assay precision

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respective NT-PCR titer for each assay

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day 1

day 2

day 3

day 4

inter-assay variability

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assay 1

1:320

assay 3

1:640

assay 4

1:640

assay 5

1:640

1:640Â± one dilution

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assay 2

1:640

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assay 6

1:640

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assay 7

1:640

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intra-assay variability

1:640Â± one dilution

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1. *R2 is the R-squared value (R-squared value is the fraction of the variance in the data that is explained by a regression); Î£R2 is the sum of R12 and R22; single well sample 1-7: a mean value resulting from two wells; b mean value resulting from three wells; c mean value resulting from four wells; NT-PCR antibody titer is highlighted in bold and underlined and corresponds to the highest Î£R2