Sensitivity, specificity and LR (+) of Gram stain to urethritis, Neisseria gonorrhoeae, Chlamydia trachomatis and Ureaplasma urealyticum
| Gram stain | Reference method | Sensitivity % (95% CI) | Specificity % (95% CI) | LR (+) (95% CI) | ||
| N=491 | + | − | ||||
| Urethritis >2 PMNLs/HPF | + | 56 | 71 | 38 (30 to 46) | 79 (75 to 84) | 1.8 (1.4 to 2.4) |
| − | 92 | 272 | ||||
| Urethritis >5 PMNLs/HPF | + | 38 | 32 | 26 (18 to 33) | 91 (87 to 94) | 2.7 (1.8 to 4.2) |
| − | 110 | 311 | ||||
| Neisseria gonorrhoeae >5 PMNLs/HPF | + | 24 | 46 | 80 (64 to 96) | ||
| − | 6 | 415 | ||||
| Chlamydia trachomatis >5 PMNLs/HPF | + | 8 | 62 | 23 (8 to 39) | ||
| − | 26 | 395 | ||||
| Ureaplasma urealyticum >5 PMNLs/HPF | + | 6 | 64 | 11 (2 to 20) | ||
| − | 49 | 372 | ||||
PMNLs/HPF, polymorphonuclear leucocytes/high-power field.
Reference methods are described in items 2, 3 and 4 of Materials and methods.