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Table 1 Performance of Xpert MTB/RIF, AFB smear microscopy and IGRA in detecting PTB, EPTB and TP

From: A retrospective study on Xpert MTB/RIF for detection of tuberculosis in a teaching hospital in China

 Sensitivity (95% CI) (%)Specificity (95% CI) (%)Positive predictive value (95% CI) (%)Negative predictive value (95% CI) (%)
Presumptive PTB cases (n = 533)
 Xpert MTB/RIF88.5 (77.0–94.6)99.6 (98.5–99.9)95.8 (86.0–98.9)98.8 (97.3–99.4)
 AFB smear microscopy36.5 (24.8–50.1)b99.0 (97.6–99.9)79.2 (59.5–90.8)93.5 (91.0–95.4)
 IGRA96.2 (87.0–98.9)55.9 (51.6–60.3) b19.1 (14.8–24.3)99.3 (97.4–99.8)
Presumptive EPTB cases (n = 172)
 Xpert MTB/RIF76.5 (52.7–90.4)99.4 (96.4–99.9)92.9 (68.5–98.7)97.5 (93.7–99.0)
 AFB smear microscopy11.8 (3.3–34.3) b99.4 (96.4–99.9)66.7 (20.8–93.9)91.1 (85.9–94.6)
 IGRA82.4 (59.0–93.8)67.1 (59.4–74.0) b21.5 (13.3–33.0)97.2 (92.1–99.0)
Presumptive TP cases (n = 82)
 Xpert MTB/RIF15.0 (5.2–36.0)100.0 (94.2–100.0)100.0 (43.9–100.0)78.5 (68.2–86.1)
 AFB smear microscopy0.0 (0.0–16.1)100.0 (94.2–100.0)NA (NA) a75.6 (65.3–83.6)
 IGRA95.0 (76.4–99.1) b45.2 (33.4–57.5) b35.9 (24.3–49.3)96.6 (82.8–99.4)
Total (n = 787)
 Xpert MTB/RIF69.7 (59.5–78.2)99.6 (98.7–99.9)95.4 (87.3–98.4)96.3 (94.6–97.4)
 AFB smear microscopy23.6 (16.0–33.4) b99.1 (98.1–99.6)77.8 (59.2–89.4)91.1 (88.8–92.9)
 IGRA93.3 (86.1–96.9) b57.5 (53.8–61.1) b21.8 (18.0–26.3)98.5 (96.8–99.3)
  1. Abbreviation: AFB acid-fast bacilli; IGRA interferon-gamma release assay; PTB pulmonary tuberculosis; EPTB extra-pulmonary tuberculosis; TP tuberculous pleurisy; CI confidence interval. a, NA, No AFB smear microscopy positive results were obtained in presumptive TP cases, thus the positive predictive value was not available. b, statistical differences between the sensitivity or specificity of AFB or IGRA and Xpert MTB/RIF, chi-square (χ2) test, P < 0.001