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Table 3 AFB smear microscopy performance for PTB and EPTB in relation to LJ culture as the reference standard

From: Diagnostic utility of GeneXpert MTB/RIF assay versus conventional methods for diagnosis of pulmonary and extra-pulmonary tuberculosis

AFB smear microscopy LJ Culture
PTB (n = 449) EPTB (n = 133)
Positive (n = 122) Negative (n = 327) Positive (n = 38) Negative (n = 95)
Positive 88 61 24 28
Negative 34 266 14 67
Sensitivity 72.1% 63.2%
Specificity 81.3% 70.5%
PPV 59.1% 46.2%
NPV 88.7% 82.7%
False -positive rate 18.7% 29.5%
False- negative rate 27.9% 36.8%
Accuracy 78.8% 68.4 %