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Table 2 Performance of Xpert MTB/RIF in different specimens

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

Specimen typeNo. (%)Xpert positive cases (%)Confirmed TB (%)Sensitivity (95% CI) (%)Specificity (95% CI) (%)Positive predictive value (95% CI) (%)Negative predictive value (95% CI) (%)
Presumptive PTB cases533 (67.7%)48 (9.0%)52 (9.8%)88.5 (77.0–94.6)99.6 (98.5–99.9)95.8 (86.0–98.9)98.8 (97.3–99.4)
 BALF204 (25.9%)7 (3.4%)7 (3.4%)85.7 (48.7–97.4)99.5 (97.2–99.9)85.7 (48.7–97.4)99.5 (97.2–99.9)
 Sputum165 (21.0%)24 (14.5%)26 (15.8%)88.5 (71.0–96.0)99.3 (96.0–99.9)95.8 (79.8–99.3)97.9 (93.9–99.3)
 FOB105 (13.3%)9 (8.6%)11 (10.5%)81.2 (52.3–94.9)100.0 (96.1–100.0)100.0 (70.1–100.0)97.9 (92.7–99.4)
 Lung tissue52 (6.6%)7 (13.5%)7 (13.5%)100.0 (64.6–100.0)100.0 (92.1–100.0)100.0 (64.6–100.0)100.0 (92.1–100.0)
 Others7 (0.9%)1 (14.3%)1 (14.3%)100.0 (20.7–100.0)100.0 (61.0–100.0)100.0 (20.7–100.0)100.0 (61.0–100.0)
Presumptive EPTB cases172 (21.9%)14 (8.1%)17 (9.9%)76.5 (52.7–90.4)99.4 (96.4–99.9)92.9 (68.5–98.7)97.5 (93.7–99.0)
 Intestine tissue53 (6.7%)1 (1.9%)0 (0%)NA#98.1 (90.1–99.7)0.0 (0.0–79.4)100.0 (93.1–100.0)
 CSF42 (5.3%)2 (4.8%)2 (4.8%)100.0 (34.2–100.0)100.0 (91.2–100.0)100.0 (34.2–100.0)100.0 (91.2–100.0)
 Ascitic fluid18 (2.3%)0 (0%)0 (0%)NA100.0 (82.4–100.0)NA100.0 (82.4–100.0)
 Joint cavity fluid13 (1.7%)2 (15.4%)2 (15.4%)100.0 (34.2–100.0)100.0 (74.1–100.0)100.0 (34.2–100.0)100.0 (74.1–100.0)
 Extrapulmonary lymph node12 (1.5%)5 (41.7%)5 (41.7%)100.0 (56.6–100.0)100.0 (64.6–100.0)100.0 (56.6–100.0)100.0 (64.6–100.0)
 Urine11 (1.4%)1 (9.1%)3 (27.3%)33.3 (6.2–79.2)100.0 (67.6–100.0)100.0 (20.7–100.0)80.0 (49.0–94.3)
 Others23 (2.9%)3 (13.0%)5 (21.7%)60.0 (23.1–88.2)100.0 (82.4–100.0)100.0 (43.9–100.0)90.0 (69.9–97.2)
Presumptive TP cases82 (10.4%)3 (3.7%)20 (24.4%)15.0 (5.2–36.0)100.0 (94.2–100.0)100.0 (43.9–100.0)78.5 (68.2–86.1)
 Pleural fluid82 (10.4%)3 (3.7%)20 (24.4%)15.0 (5.2–36.0)100.0 (94.2–100.0)100.0 (43.9–100.0)78.5 (68.2–86.1)
Total78765 (8.3%)89 (11.3%)69.7 (59.5–78.2)99.6 (98.7–99.9)95.4 (87.3–98.4)96.3 (94.6–97.4)
  1. Abbreviation: PTB pulmonary tuberculosis; EPTB extra-pulmonary tuberculosis; TP tuberculous pleurisy; CI confidence interval; BALF bronchoalveolar lavage fluid; FOB Fiberoptic bronchoscopy; CSF Cerebrospinal fluid. #, NA, No Xpert positive results (and no confirmed TB cases) were obtained, thus the sensitivity (and positive predictive value) was not available