Evaluation of the ligase chain reaction (LCx) assay in culture confirmed Mycobacterium tuberculosis infection
| Culture positive for M tuberculosis (n = 131) | Culture negative for M tuberculosis (n = 1989) | |||||||
|---|---|---|---|---|---|---|---|---|
| Specimens (no.) | LCx positive | LCx negative | LCx positive | LCx negative | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) |
| *Sixty eight were contaminated cultures. | ||||||||
| **Nine were positive by culture for non-tuberculous mycobacteria; six were culture negative. | ||||||||
| NPV, negative predictive value; PPV, positive predictive value. | ||||||||
| All (2120) | 109 | 22 | 33 | 1956* | 85.6 | 98.4 | 79.9 | 98.9 |
| Smear positive (114) | 91 | 1 | 7 | 15** | 98.9 | 75.9 | 92.9 | 95.7 |
| Smear negative (2006) | 18 | 21 | 26 | 1941 | 65.0 | 98.7 | 60.0 | 98.9 |
| Respiratory (2058) | 91 | 21 | 33 | 1913 | 84.2 | 98.3 | 77.2 | 98.9 |
| Non-respiratory (49) | 5 | 1 | 0 | 43 | 85.7 | 100.0 | 100.0 | 97.7 |
| Quality control (13) | 10 | 0 | 0 | 3 | 100.0 | 100.0 | 100.0 | 100.0 |