Study population, demographics and sexual behaviours among men who have sex with men (MSM) attending Public Health—Seattle & King County (PHSKC) STD Clinic (N=33 472) between 1 January 2001 and 31 December 2013
| Total study population* N=33 472† | Controls: no urethral infection N=25 705 (76.8%) | Cases: symptomatic urethritis n=5277 (15.8%) | Asymptomatic urethritis n=1112 (3.3%) | |
|---|---|---|---|---|
| Patient reported urethral symptoms (N, %) | 6655 (19.9) | 5277 (100) | ||
| Age (mean, SD) | 35.5 (10.9) | 35.6 (11.2) | 34.9 (9.7) | 33.7 (10.4) |
| Race‡ (N, %) | ||||
| White | 23 370 (73.0) | 17 847 (69.4) | 3771 (74.8) | 765 (68.8) |
| Black | 2457 (7.7) | 1747 (6.8) | 492 (9.8) | 94 (8.5) |
| Hispanic | 1935 (6.1) | 1561 (6.1) | 250 (5.0) | 74 (6.7) |
| Asian | 1938 (6.1) | 1635 (6.4) | 207 (4.1) | 51 (4.6) |
| Native American/Alaskan native | 390 (1.2) | 300 (1.2) | 54 (1.1) | 17 (1.5) |
| Other | 1907 (6.0) | 1485 (5.8) | 268 (5.3) | 65 (5.8) |
| Number of sex partners in the past 2 months (median, IQR) | 3.7 (3) | 3.8 (3) | 3.3 (3) | 3.5 (3) |
| Sexual behaviours in the past 2 months (N, %) | ||||
| Only oral sex (IOS) | 5131 (15.3) | 4148 (16.1) | 639 (12.1) | 108 (9.7) |
| Protected insertive anal intercourse and oral sex (PIAI) | 7691 (23.0) | 6106 (23.8) | 1065 (20.2) | 210 (18.9) |
| Unprotected insertive anal intercourse (UIAI) | 19 898 (59.5) | 14 817 (57.6) | 3501 (66.3) | 777 (69.9) |
| Vaginal sex | 412 (1.2) | 355 (1.4) | 29 (0.6) | 12 (1.1) |
| None | 340 (1.0) | 279 (1.1) | 43 (0.8) | 5 (0.4) |
| HIV-positive (N, %) | 3923 (11.7) | 2738 (10.7) | 870 (16.5) | 149 (13.4) |
| Urethral infections by aetiology | ||||
| Gonorrhoea | 1614 (4.8) | 1509 (28.6) | 95 (8.5) | |
| Chlamydia | 1119 (3.3) | 599 (11.4) | 455 (40.9) | |
| Non-gonococcal non-chlamydial urethritis (NGNCU) | 3482 (10.4) | 2935 (55.6) | 547 (49.2) | |
| Gonorrhoea and chlamydia | 249 (0.7) | 234 (4.4) | 15 (1.4) | |
*MSM new problem visits with complete data to permit categorisation based on sexual behaviours.
†Includes 1378 (4.1%) visits in which men complained of urethral symptoms but were not diagnosed with urethritis by our definition. This included 75 with positive tests for gonorrhoea and/or chlamydia. These 1378 are excluded from the case–control and asymptomatic infection analyses.
‡Percentages do not add to 100% due to non-response on some items.