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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