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Table 4 Comparison of Xpert® Ct scores and Time-To-Culture Positivity (TTP)

From: Performance evaluation of three commercial molecular assays for the detection of Mycobacterium tuberculosis from clinical specimens in a high TB-HIV-burden setting

Study Number

TTP

Probe D

Probe C

Probe E

Probe B

Probe A

Xpert® interpretation

Ave Ct

TTP <20d

 138

11

20.8

19.3

20.8

21.3

19.2

Medium

20.28

 122

14

20.9

19

20

22.3

18.6

Medium

20.16

 127

14

14.7

13.3

15.2

14.9

13.2

High

14.22

 130

14

16.5

15.1

16.5

16.6

14.9

High

15.92

 132

14

20.7

19.2

20.6

20.3

19

Medium

19.96

 142

14

17.9

16.6

18.1

0

16.5

Medium

13.82

 144

15

26.3

25.0

26.3

26.3

24.7

Low

25.72

 147

15

26.7

25.5

27.1

26.6

25.4

Low

26.26

 131

16

28.1

26.6

28.2

28.1

26.6

Low

27.52

 139

16

34

33

34.8

33.3

33

Low

33.62

 121

18

32.9

31.8

33.7

32.2

32.1

Very Low

32.54

 145

19

Not detected

TTP ≥20d

 133

20

23.2

21.7

23.2

23.2

21.6

Medium

22.58

 136

21

Not detected

 146

21

26.9

25.4

26.9

26.9

25.4

Low

26.3

 120

21

20.4

18.8

20.1

20.3

18.7

Medium

19.66

 124

21

35.1

33.8

36.1

34.3

34.1

Very Low

34.68

 125

21

33.7

32.5

34.5

33.0

32.6

Very Low

33.26

 126

21

Not detected

 137

21

Not detected

 

 128

22

27.3

25.9

27.3

27.4

25.8

Low

26.74

 129

22

23.6

22.1

23.6

23.5

22.0

Medium

26.74

 134

22

21.3

19.7

21.2

21.2

19.5

Medium

20.58

 119

23

26.9

25.8

27

26.7

25.6

Low

26.4

 135

26

24.1

22.8

24.1

24.1

22.5

Low

23.52

 123

30

Not Detected