Table 2. Results of LiPA in detecting rifampin resistance in specimens from which MTBC was correctly identified and cultured*.
| Sample and AFB smear result | No. positive/no. tested (%) |
|||||
|---|---|---|---|---|---|---|
| Concordance | Sensitivity | Specificity | PPV | NPV | Mean days saved | |
| All primary LiPA | 775/782 (99.1) | 38/40 (95.0) | 737/740 (99.6) | 38/41 (92.7) | 738/740 (99.7) | 30.7 |
| Positive | 743/747 (99.5) | 35/36 (97.2) | 708/710 (99.7) | 35/37 (94.6) | 709/710 (99.9) | 30.4 |
| Negative | 32/35 (91.4) | 3/4 (75.0) | 29/30 (96.7) | 3/4 (75.0) | 29/30 (96.7) | 37.2 |
| Not done | – | – | – | – | – | – |
| Respiratory | 669/672 (99.6) | 32/33 (97.0) | 637/639 (99.7) | 32/34 (94.1) | 637/638 (99.8) | 30.4 |
| Positive | 654/657 (99.5) | 31/32 (96.9) | 623/625 (99.7) | 31/33 (93.9) | 623/624 (99.8) | 30.2 |
| Negative | 15/15 (100.0) | 1/1 (100.0) | 14/14 (100.0) | 1/1 (100.0) | 14/14 (100.0) | 39.1 |
| Not done | – | – | – | – | – | – |
| Nonrespiratory | 106/110 (96.4) | 6/7 (85.7) | 100/101 (99.0) | 6/7 (85.7) | 101/102 (99.0) | 32.5 |
| Positive | 89/90 (98.9) | 4/4 (100.0) | 85/85 (100.0) | 4/4 (100.0) | 86/86 (100.0) | 32.0 |
| Negative | 17/20 (85.0) | 2/3 (66.7) | 15/16 (93.8) | 2/3 (66.7) | 15/16 (93.8) | 35.5 |
| Not done | – | – | – | – | – | – |
| Clinical isolate | 229/235 (97.4) | 21/23 (91.3) | 208/211 (98.6) | 21/24 (87.5) | 208/210 (99.0) | 16.3 |
*LiPA, line probe assay; MTBC, Mycobacterium tuberculosis complex; AFB, acid-fast bacilli; PPV, positive predictive value; NPV, negative predictive value.