TABLE 3.
Comparative efficiencies of PK-Roche and CTAB-Roche extraction methods for the amplification of M. tuberculosis DNA from 144 specimens after removal of inhibitory activity by serial dilution compared to culturea
| Method | Status | No. of specimens culture:
|
Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | |
|---|---|---|---|---|---|---|---|
| P | N | ||||||
| PK-PCR | P | 3 | 3 | ||||
| N | 8 | 120 | 27.2 | 97.6 | 50 | 93.8 | |
| I | 4 | 6 | |||||
| CTAB-PCR | P | 11 | 24 | ||||
| N | 2 | 98 | 84.6 | 75.5 | 31.4 | 98 | |
| I | 2 | 7 | |||||
a
P, positive; N, negative; I, inhibitory; PPV, positive predictive value; NPV, negative predictive value. Cutoff absorbance value, >0.300.