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Table 5 Hypothetical Predictive Values of Xpert detection of RIF resistance vs. DST

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 Prevalence of RIF resistance among MTB culture positive Probability of RIF Resistance among Xpert results “MTB detected RIF Resistance detected” Percent of Xpert results “MTB detected RIF Resistance detected” in the population Probability of RIF Resistance among Xpert results “MTB detected, RIF Resistance not detected”
5% 1.0% 48.4% 0.09% 0.04%
1.5% 58.6% 0.11% 0.06%
2.0% 65.5% 0.13% 0.08%
10% 91.2% 0.47% 0.45%
50% 98.9% 2.17% 3.39%
11.8% 1.0% 48.4% 0.21% 0.05%
1.5% 58.6% 0.26% 0.07%
2.0% 65.5% 0.31% 0.10%
10% 91.2% 1.11% 0.51%
50% 98.9% 5.11% 4.16%
20% 1.0% 48.4% 0.35% 0.05%
1.5% 58.6% 0.44% 0.07%
2.0% 65.5% 0.52% 0.10%
10% 91.2% 1.88% 0.54%
50% 98.9% 8.66% 4.46%