Performance of the ligase chain reaction (LCx) assay compared with culture and microscopy in clinically resolved cases of tuberculosis (TB)
| Clinical diagnosis | ||||||
|---|---|---|---|---|---|---|
| Test method and outcome (no.)* | TB+ (n = 164) | TB− (n = 1956) | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) |
| *Includes specimens subject to repeat testing after diagnosis and initiation of treatment. | ||||||
| **LCx is more sensitive than culture because patients on treatment who become culture negative remain LCx positive. | ||||||
| NPV, negative predictive value; PPV, positive predictive value. | ||||||
| LCx assay | ||||||
| Positive (142) | 142 | 0 | 88.2** | 100.00 | 100.00 | 98.9 |
| Negative (1978) | 22 | 1956 | ||||
| Auramine staining | ||||||
| Positive (114) | 99 | 15 | 60.4 | 99.2 | 91.6 | 96.8 |
| Negative (2006) | 65 | 1941 | ||||
| Culture | ||||||
| Positive (131) | 131 | 0 | 83.2** | 100.00 | 100.00 | 98.3 |
| Negative (1989) | 33 | 1956 | ||||