General characteristics of the women living in Amsterdam participating in the National Chlamydia Screening trial included in this study, at baseline
| Controls n=55 | Cases n=60 | p Value | |
| Median age (IQR) | 22 (19–25) | 23 (20–25) | 0.41 |
| Median age of first sexual contact (IQR) | 16 (15–17) | 16 (15–17) | 0.52 |
| Born in the Netherlands | 46 (83.6%) | 50 (83.3%) | 0.96 |
| Ethnicity | 0.98 | ||
| Dutch | 39 (70.9%) | 41 (68.3%) | |
| Surinamese/Dutch Antilles | 11 (20.0% | 13 (21.7%) | |
| Asian | 3 (5.4.9%) | 3 (5.0%) | |
| Turkish | 1 (1.7%) | 1 (1.8%) | |
| Education | 0.28 | ||
| Low | 2 (3.6%) | – | |
| Middle | 23 (41.9%) | 22 (36.7%) | |
| High | 28 (50.9%) | 34 (56.7%) | |
| Sexual partners in the previous 6 months (IQR) | 1 (1–2) | 2 (1–3) | 0.07 |
| Previous infection with Chlamydia trachomatis* | 3 (5.5%) | 9 (15.0%) | 0.09 |
| Sexual health problems† | 6 (10.9%) | 13 (21.7%) | 0.27 |
| Relationship | 0.21 | ||
| Living together | 6 (10.9%) | 2 (3.3%) | |
| Living apart | 17 (30.9%) | 14 (23.3%) | |
| Single | 25 (45.5%) | 31 (51.7%) |
*Self-reported.
†Self-reported complaints such as having more vaginal discharge than normal, a burning sensation while urinating, abdominal pain, and blood loss between menses, or during or after sexual intercourse.