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Table 3 Sensitivity, specificity, and Predictive values of AFB smear and Xpert MTB/RIF assay using culture as a gold standard

From: Xpert MTB/RIF assay for diagnosis of pulmonary tuberculosis in sputum specimens in remote health care facility

Method and test type Sensitivity %(95 % CI) Specificity %(95 % CI) PPV %(95 % CI) NPV %(95 % CI)
AFB Smear 36.2 (23.8–48.6) 99 4 (98.2–100) 95.5 (86.8–100) 81.3 (75.9–86.7)
GeneXpert MTB/RIF assay     
 Smear negative 48.6(32.5–64.8) 96.9(94.2–99.6) 78.3(61.4–95.1) 89.1(84.5–93.8)
 Smear positive 95.2(86–100) N/Aa 95.2(86–100) N/A
 Total (SPTB & SNTB) 65.5(53.3–77.7) 96.3 (93.4–992) 86.4(76.2–96.5) 88.6(83.9–93.3)
  1. aN/A – Not applicable, SPTB – Smear positive TB, SNTB – Smear negative TB