Table 3.

Xpert® MTB/RIF assay performance compared with MGIT culture and smear microscopy

	Sensitivity (95% CI)	Specificity (95% CI)	PPV	NPV
Xpert® MTB/RIF assay versus MGIT
All patients*	21/26 (80.8%) [60.0–92.7%]†	66/68 (97.1%) [88.8–99.5%]	91.3% [70.5–98.5%]	93.0% [83.7–97.4%]
HIV negative	3/3 (100%) [31.0–100%]	19/19 (100%) [79.1–100%]	100% [31.0–100%]	100% [79.1–100%]
HIV positive	17/21 (80.1%) [57.4–93.7%]‡	39/41 (95.1%) [82.2–99.2%]	89.5% [65.5–98.2%]	90.7% [76.9–97.0%]
Sputum smear microscopy versus MGIT
All patients	13/26 (50.0%) [30.4–69.6%]†	66/66 (100%) [93.3–100%]	100% [71.7–100%]	84.0% [73.8–90.8%]
HIV negative	2/3 (66.7%) [12.5–98.2%]	19/19 (100%) [79.1–100%]	100% [19.8–100%]	95.0% [73.1–99.7%]
HIV positive	10/21 (47.6%) [26.4–69.7%]‡	41/41 (100%) [89.3–100%]	100% [65.5–100%]	78.8% (65.5–88.5%]

Data displayed as number correct/number tested, (%) [95% CI]; PPV, positive predictive value; NPV, negative predictive value.

^*The Xpert® MTB/RIF assay gave repeat errors in 3 samples and is excluded from this analysis. Fisher's exact test:

^†P = 0.02

^‡P = 0.03.