Evaluation of the ligase chain reaction (LCx) assay in clinically resolved cases of Mycobacterium tuberculosis infection (culture results and clinical data)
| No. resolved as positive for M tuberculosis (n = 164) | No. resolved as negative for M tuberculosis (n = 1956) | |||||||
|---|---|---|---|---|---|---|---|---|
| Specimens (n = 2120) | 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) | 142 | 22 | 0 | 1956* | 88.2 | 100.0 | 100.0 | 98.9 |
| Smear positive (114) | 98 | 1 | 0 | 15** | 99.0 | 100.0 | 100.0 | 93.8 |
| Smear negative (2006) | 44 | 21 | 0 | 1941 | 75.6 | 100.0 | 100.0 | 98.9 |
| Respiratory (2058) | 124 | 22 | 0 | 1913* | 86.9 | 100.0 | 100.0 | 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 |