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Table 1 Performance of the Xpert MTB/RIF assay as stratified by smear status

From: Performance evaluation of the Xpert MTB/RIF assay according to its clinical application

Performance of the Xpert MTB/RIF assay Total ( n =303) Total ( n =271) a Smear result (total, n =271) a
No./Total no.% (95% CI)    Smear-positive ( n =100) Smear-negative ( n =171)
Sensitivity 95/104 95/104 76/79 19/25
91.3 (83.8-95.7) 91.3 (83.8-95.7) 96.2 (88.5-99.0) 76.0 (54.5-89.8)
Specificity 175/199 157/167 18/21 139/146
87.9 (82.4-92.0) 94.0 (89.0-96.9) 85.7 (62.6-96.2) 95.2 (90.0-97.9)
PPV 95/119 95/105 76/79 19/26
79.8 (71.3-86.4) 90.5 (82.8-95.1) 96.2 (88.5-99.0) 73.1 (51.9-87.6)
NPV 175/184 157/166 18/21 139/145
95.1 (90.6-97.6) 94.6 (89.6-97.3) 85.7 (62.6-96.2) 95.9 (90.8-98.3)
  1. Abbreviations: CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value.
  2. aExcluding the 32 culture-negative samples from patients who were currently receiving anti-tuberculosis treatment.