Rifampicin resistance prevalence % | PPV % | NPV % | True positive¶ | False negative¶ | False positive¶ | True negative¶ |
1 | 32.4 | 99.9 | 9.5 | 0.5 | 19.8 | 970.2 |
2 | 49.2 | 99.9 | 19 | 1 | 19.6 | 960.4 |
3 | 59.5 | 99.8 | 28.5 | 1.5 | 19.4 | 950.6 |
4 | 66.4 | 99.8 | 38 | 2 | 19.2 | 940.8 |
5 | 71.4 | 99.7 | 47.5 | 2.5 | 19 | 931 |
6 | 75.2 | 99.7 | 57 | 3 | 18.8 | 921.2 |
7 | 78.1 | 99.6 | 66.5 | 3.5 | 18.6 | 911.4 |
8 | 80.5 | 99.6 | 76 | 4 | 18.4 | 901.6 |
9 | 82.4 | 99.5 | 85.5 | 4.5 | 18.2 | 891.8 |
10 | 84.1 | 99.4 | 95 | 5 | 18 | 882 |
11 | 85.4 | 99.4 | 104.5 | 5.5 | 17.8 | 872.2 |
12 | 86.6 | 99.3 | 114 | 6 | 17.6 | 862.4 |
13 | 87.7 | 99.2 | 123.5 | 6.5 | 17.4 | 852.6 |
14 | 88.5 | 99.2 | 133 | 7 | 17.2 | 842.8 |
15 | 89.3 | 99.1 | 142.5 | 7.5 | 17 | 833 |
20 | 92.2 | 98.7 | 190 | 10 | 16 | 784 |
25 | 94.1 | 98.3 | 237.5 | 12.5 | 15 | 735 |
PPV: positive predictive value; NPV: negative predictive value. #: according to varying prevalences of rifampicin resistance in a sample population of 1000 individuals; ¶: sensitivity (95%) and specificity (98%) for Xpert MTB/RIF rifampicin resistance, compared with reference method (culture).