Table 2.
Performance of Xpert MTB/RIF assay using mycobacterial culture as the reference standard
| Positive | Negative | Sensitivity | Specificity | Accuracy | PPV | NPV | ||
|---|---|---|---|---|---|---|---|---|
| SX | Positive | 6 | 25 | 60.0% (6/10) (26.2–87.8%) |
71.6% (63/88) (61.0–80.7%) |
70.4% (69/98) (60.3–79.2%) |
19.4% (6/31) (7.5–37.5%) |
94.0% (63/67) (85.4–98.3%) |
| Negative | 4 | 63 | ||||||
| BX | Positive | 14 | 35 | 87.5% (14/16) (61.7–98.4%) |
62.0% (57/92) (51.2–71.9%) |
65.7% (71/108) (56.0–74.6%) |
28.6% (14/49) (16.6–43.3%) |
96.6% (57/59) (88.3–99.6%) |
| Negative | 2 | 57 |
SX, sputum Xpert; BX, BALF Xpert; PPV, positive predictive value; NPV, negative predictive value.