Table 4 GeneXpert MTB/RIF diagnostic system performance for PTB and EPTB in relation to LJ culture as the reference standard
Specimen type | PTB (n = 449) | EPTB (n = 133) | PTB | EPTB | |||||
|---|---|---|---|---|---|---|---|---|---|
Sputum | BAL | Pleural fluid | CSF | Ascetic fluid | Pus | Urine | |||
No. | 430 (95.8 %) | 19 (4.2 %) | 26 (19.5 %) | 62 (46.6 %) | 19 (14.3 %) | 12 (9.0 %) | 14 (10.5 %) | 449 | 133 |
True- positive | 106 | 4 | 7 | 12 | 5 | 3 | 3 | 110 | 31 |
False- positive | 0 | 1 | 2 | 4 | 1 | 0 | 1 | 1 | 9 |
True- negative | 272 | 12 | 13 | 40 | 11 | 5 | 7 | 284 | 75 |
False negative | 12 | 0 | 2 | 1 | 1 | 2 | 2 | 12 | 7 |
Invalid or error | 40 (9.3 %) | 2 (10.5 %) | 2 (7.7 %) | 5 (8.1 %) | 1 (5.3 %) | 2 (16.7 %) | 1 (7.1 %) | 42 (9.4 %) | 11 (8.3 %) |
Sensitivity | 89.8% | 100% | 77.8% | 92.3% | 83.3% | 60.0% | 60.0% | 90.2% | 81.6% |
Specificity | 87.2% | 80.0% | 76.5% | 81.6% | 84.6% | 71.4% | 77.8% | 86.9% | 78.9% |
PPV | 100 % | 80.0% | 77.8% | 75.0% | 83.3% | 100% | 75% | 99.1% | 77.5% |
NPV | 95.8 | 100% | 86.7% | 97.6% | 91.7% | 71.4% | 77.8% | 95.9% | 91.5% |
False- positive rate | 0.0% | 20% | 11.8% | 10.2% | 7.7% | 0.0% | 11.1% | 0.3% | 9.5% |
False -negative rate | 4.2% | 0% | 22.2% | 0% | 16.7% | 40.0% | 40.0% | 9.8% | 18.5 % |