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Table 4 Hypothetical Predictive Values of Xpert detection of MTBc vs. MTB Culture

From: Performance of the G4 Xpert® MTB/RIF assay for the detection of Mycobacterium tuberculosis and rifampin resistance: a retrospective case-control study of analytical and clinical samples from high- and low-tuberculosis prevalence settings

Prevalence of MTB culture positive Probability of MTB culture positive among Probability of MTB culture negative among
Xpert MTB detected AFB Smear Pos. Xpert MTB detected AFB Smear Neg. Xpert MTB not detected
1% 82.9 14.4 99.9
2% 90.8 25.4 99.9
3% 93.7 34.1 99.8
4% 95.2 41.0 99.7
5% 96.2 46.8 99.7
10% 98.2 65.0 99.3
11.8% 98.5% 69.1% 99.2%
20% 99.2 80.7 98.5
40% 99.7 91.8 96.1
50% 99.8 94.4 94.2