Results of LiPA compared with culture in detecting Mycobacterium tuberculosis complex (2003–2009 in comparison to 1999–2002)
| Sample and AFB smear results | 1999–2002 | 2003–2009 | Statistics comparison (χ2 test) | ||||||
| Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | ||
| All† ‡ | 782/918 (85.2) | 886/1004 (88.2) | 782/900 (86.9) | 886/1022 (86.7) | 2876/3296 (87.3) | 4137/4540 (91.1) | 2876/3279 (87.7) | 4137/4557 (90.8) | |
| All smear +ve | 747/796 (93.6) | 213/301 (70.8) | 747/835 (89.5) | 213/264 (80.7) | 2421/2604 (93.0) | 782/1032 (75.8) | 2421/2671 (90.6) | 782/965 (81.0) | |
| All smear −ve | 35/119 (29.4)* | 644/673 (95.7) | 35/64 (54.7) | 644/728 (88.5) | 260/438 (59.4)* | 2522/2638 (95.6) | 260/376 (69.1) | 2522/2700 (93.4) | *p=0.0005 |
| Respiratory† | 672/738 (91.1) | 496/560 (88.6) | 672/736 (91.3) | 496/562 (88.3) | 2375/2595 (91.5) | 1628/1825 (89.2) | 2375/2572 (92.3) | 1628/1848 (88.1) | |
| Respiratory smear +ve | 657/696 (94.4) | 170/219 (77.6) | 657/706 (93.1) | 170/209 (81.3) | 2083/2221 (93.8) | 644/782 (82.4) | 2083/2221 (93.8) | 644/782 (82.4) | |
| Respiratory smear −ve | 15/42 (35.7)** | 313/327 (95.7) | 15/29 (51.7) | 313/340 (92.1) | 145/206 (70.4)** | 829/867 (95.6) | 145/183 (79.2) | 829/890 (93.1) | **p=0.039 |
| Non-respiratory† | 110/180 (61.1) | 390/444 (87.8) | 110/164 (67.1) | 390/960 (84.8) | 500/700 (71.4) | 2500/2706 (92.4) | 500/706 (70.8) | 2500/2700 (92.6) | |
| Non-respiratory smear +ve | 90/102 (88.2) | 43/82 (52.4) | 90/129 (69.8) | 43/55 (78.2) | 328/373 (87.9) | 137/246 (55.7) | 328/437 (75.1) | 137/182 (75.3) | |
| Non-respiratory smear −ve | 20/77 (26.0)*** | 331/346 (95.7) | 20/35 (57.1) | 331/388 (85.3) | 114/231 (49.4)*** | 1690/1768 (95.6) | 114/192 (59.4) | 1690/1807 (93.5) | ***p=0.018 |
*There is a statistically significant increase in the sensitivity of the LiPA testing of all smear negative samples by time (p=0.0005).
**There is a statistically significant increase in the sensitivity of the LiPA testing of smear negative respiratory samples by time (p=0.039).
***There is statistically significant increase in the sensitivity of the LiPA testing smear negative non-respiratory samples by time (p=0.018).
↵† Smear negative + smear positive + smear unknown.
↵‡ Respiratory samples + non-respiratory samples + unclassified samples.
AFB, acid-fast bacilli; NPV, negative predictive value; PPV, positive predictive value; −ve, negative; +ve, positive.