Comparison of Xpert MTB/RIF Assay and the Conventional Sputum Microscopy in Detecting Mycobacterium tuberculosis in Northern Thailand

Table 3

Sensitivity, specificity, positive predictive value, and negative predictive value of Xpert assay and sputum acid-fast smear comparing to sputum culture.

	Xpert assay	95% confidence interval	Acid-fast smear	95% confidence interval
Specimens from all patients ()
SEN	41/43 = 95.3%	84.2–99.4%	26/43 = 60.5%	44.4–75.0%
SPEC	57/66 = 86.4%	75.7–93.6%	65/66 = 98.5%	91.8–100%
PPV	41/50 = 82.0%	68.6–91.4%	26/27 = 96.3%	81.0–99.9%
NPV	57/59 = 96.6%	88.3–99.6%	65/82 = 79.3%	68.9–87.4%
Specimens from HIV-infected patients ()
SEN	10/10 = 100%	69.2–100%	6/10 = 60%	26.2–87.8%
SPEC	16/16 = 100%	79.4–100%	19/19 = 100%	82.4–100%
PPV	10/13 = 76.9%	46.2–95.0%	6/6 = 100%	54.1–100%
NPV	16/16 = 100%	79.4–100%	19/23 = 80%	61.2–95.0%
Specimens from HIV-uninfected patients ()
SEN	28/30 = 93.3%	77.9–99.2%	20/30 = 66.7%	47.2–82.7%
SPEC	41/43 = 95.3%	84.2–99.4%	46/47 = 97.9%	88.7–99.9%
PPV	28/34 = 82.4%	65.5–93.2%	20/21 = 95.2%	76.2–99.9%
NPV	41/43 = 95.3%	84.2–99.4%	46/56 = 82.1%	69.6–91.1%

SEN: sensitivity; SPEC: specificity; PPV: positive predictive value; NPV: negative predictive value.