Sensitivity, specificity, positive and negative predictive value of culture, ligase chain reaction and strand displacement amplification compared with resolved positive tests to detect Chlamydia trachomatis and Neisseria gonorrhoeae
| Resolved positive | Sensitivity, n (%) | 95% CI (%) | Specificity (%) | 95% CI (%) | Sample PPV, n (%) | Sample NPV,n (%) | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| + | − | Total | ||||||||
| LCR, ligase chain reaaction; NA, not applicable; NPV, negative predictive value; PPV, positive predictive value; SDA, strand displacement amplification. | ||||||||||
| *Prevalence is derived from number of positives according to the definition of a resolved positive test (pharynx and rectum). Prevalence of urethral C trachomatis and N gonorrhoeae is derived from number of positive LCR samples. | ||||||||||
| †Culture was performed on the first 270 samples only; 14 pharyngeal and 48 rectal samples were toxic to culture. | ||||||||||
| ‡Performance of culture is compared with LCR. | ||||||||||
| In all, 21 of 96 (21.9%) people with N gonorrhoeae were coinfected with C trachomatis. | ||||||||||
| C trachomatis | ||||||||||
| Pharynx (prevalence 1.2%)* | ||||||||||
| Culture† | ||||||||||
| + | 1 | 0 | 1 | 1/1 (100) | NA | NA | NA | NA | 242/242 (100) | |
| − | 0 | 242 | 242 | |||||||
| Total | 1 | 242 | 243 | |||||||
| LCR | ||||||||||
| + | 7 | 5 | 12 | 7/7 (100) | 59.0 to 100 | 587/592 (99.2) | 98.0 to 99.7 | 7/12 (58.3) | 587/587 (100) | |
| − | 0 | 587 | 587 | |||||||
| Total | 7 | 592 | 599 | |||||||
| SDA | ||||||||||
| + | 7 | 0 | 7 | 7/7 (100) | 59.0 to 100 | 592/592 (100) | 99.4 to 100 | 7/7 (100) | 592/592 (100) | |
| − | 0 | 592 | 592 | |||||||
| Total | 7 | 592 | 599 | |||||||
| Urethra (prevalence 4.3%, 26/599 using LCR)* | ||||||||||
| Rectum (prevalence 6.5%)* | ||||||||||
| Culture† | ||||||||||
| + | 3 | 0 | 3 | 3/11 (27.3) | 6.0 to 61.0 | NA | NA | NA | 198/206 (96.1) | |
| − | 8 | 198 | 206 | |||||||
| Total | 11 | 198 | 209 | |||||||
| LCR | ||||||||||
| + | 39 | 8 | 47 | 39/39 (100) | 91.0 to 100 | 552/560 (98.6) | 97.2 to 99.4 | 39/47 (83.0) | 552/552 (100) | |
| − | 0 | 552 | 552 | |||||||
| Total | 39 | 560 | 599 | |||||||
| SDA | ||||||||||
| + | 36 | 3 | 39 | 36/39 (92.3) | 79.1 to 98.4 | 557/560 (99.5) | 98.4 to 99.9 | 36/39 (92.3) | 557/560 (99.5) | |
| − | 3 | 557 | 560 | |||||||
| Total | 39 | 560 | 599 | |||||||
| N gonorrhoeae | ||||||||||
| Pharynx (prevalence 7.3%)* | ||||||||||
| Culture | ||||||||||
| + | 17 | 0 | 17 | 17/44 (38.6) | 24.4 to 54.5 | NA | NA | NA | 555/582 (95.4) | |
| − | 27 | 555 | 582 | |||||||
| Total | 44 | 555 | 599 | |||||||
| LCR | ||||||||||
| + | 44 | 12 | 56 | 44/44 (100) | 92.0 to 100 | 543/555 (97.8) | 96.3 to 98.9 | 44/56 (78.6) | 543/543 (100) | |
| − | 0 | 543 | 543 | |||||||
| Total | 44 | 555 | 599 | |||||||
| SDA | ||||||||||
| + | 39 | 25 | 64 | 39/44 (88.6) | 75.4 to 96.2 | 530/555 (95.5) | 93.4 to 97.1 | 39/64 (60.9) | 530/535 (99.1) | |
| − | 5 | 530 | 535 | |||||||
| Total | 44 | 555 | 599 | |||||||
| Urethra (prevalence 7.2%, 43/599 using LCR)* | ||||||||||
| Culture‡ | ||||||||||
| + | 39 | 0 | 39 | 39/43 (90.7) | 77.9 to 97.4 | NA | NA | NA | 555/559 (99.3) | |
| − | 4 | 555 | 560 | |||||||
| Total | 43 | 555 | 598 | |||||||
| Rectum (prevalence 7.3%)* | ||||||||||
| Culture | ||||||||||
| + | 38 | 0 | 38 | 38/44 (86.4) | 72.6 to 94.8 | NA | NA | NA | 555/561 (98.9) | |
| − | 6 | 555 | 561 | |||||||
| Total | 44 | 555 | 599 | |||||||
| LCR | ||||||||||
| + | 42 | 5 | 47 | 42/44 (95.5) | 84.5 to 99.4 | 550/555 (99.1) | 97.9 to 99.7 | 42/47 (89.4) | 550/552 (99.6) | |
| − | 2 | 550 | 552 | |||||||
| Total | 44 | 555 | 599 | |||||||
| SDA | ||||||||||
| + | 43 | 5 | 48 | 43/44 (97.7) | 88.0 to 99.9 | 550/555 (99.1) | 97.9 to 99.7 | 43/48 (89.6) | 550/551 (99.8) | |
| − | 1 | 550 | 551 | |||||||
| Total | 44 | 555 | 599 | |||||||