Incidence rate of chlamydial infection among 16–24-year-old women per 100 person-years by setting of recruitment and population characteristics, England, March 2002–August 2003
| Characteristic | Recruited from general practice | Recruited from family planning | Recruited from GUM | |||
|---|---|---|---|---|---|---|
| n (number of positives) | Incidence rate per 100 py (95% CI) | n (number of positives) | Incidence rate per 100 py (95% CI) | n (number of positives) | Incidence rate per 100 py (95% CI) | |
| GUM, genitourinary medicine; py, person-years; ref, reference group for significance test. | ||||||
| *The rate of new sexual partner change for the time period immediately preceding infection. | ||||||
| †Result of significance test suggests incidence rate is different from the reference group at p<0.05 level. | ||||||
| ‡Rate based on very small sample size (n = 6); probably not generalisable outside study population. | ||||||
| Total recruited | 353 | 546 | 525 | |||
| Total retained for follow-up | 203 (11) | 4.9 (2.7 to 8.8) ref | 306 (21) | 6.4 (4.2 to 9.8) | 268 (30) | 10.6 (7.4 to 15.2) |
| Retention rate | 58% | 56% | 57% | |||
| Reason for attendance (baseline) | ||||||
| Attended for symptoms | 17 (0) | No events | 21 (3) | 14.3 (4.6 to 44.2) | 76 (9) | 10.5 (5.5 to 20.2) |
| Other reason, but reported symptoms | 54 (5) | 8.0 (3.3 to 19.1) | 86 (3) | 3.2 (1.0 to 9.9) | 56 (7) | 12.4 (5.9 to 25.9) |
| Asymptomatic | 132 (6) | 4.1 (1.9 to 9.2) | 199 (15) | 7.0 (4.2 to 11.6) | 136 (14) | 10.0 (5.9 to 16.8) |
| Age group (years) | ||||||
| 16–17 | 33 (4) | 11.2 (4.2 to 29.8) | 92 (9) | 9.5 (5.0 to 18.3) | 48 (5) | 10.1 (4.2 to 24.4) |
| 18–20 | 83 (3) | 3.1 (1.0 to 9.6) | 117 (5) | 3.7 (1.5 to 8.8) | 110 (16) | 14.1 (8.6 to 23.0) |
| 21–24 | 87 (4) | 4.3 (1.6 to 11.4) | 97 (7) | 7.1 (3.4 to 14.8) | 110 (9) | 7.5 (3.9 to 14.5) |
| Ethnic group | ||||||
| White | 151 (8) | 4.6 (2.3 to 9.1) | 253 (20) | 7.3 (4.7 to 11.3) | 185 (21) | 10.3 (6.7 to 15.8) ref |
| Non-white | 0 | No events | 2 (0) | No events | 4 (2) | 105.0 (26.2 to 419.7)†‡ |
| Unknown | 52 (3) | 5.9 (1.9 to 18.1) | 51 (1) | 1.9 (0.3 to 13.3) | 79 (7) | 9.2 (4.4 to 19.2) |
| Ever had chlamydia (baseline) | 1 | |||||
| Yes | 2 (1) | 8.5 (1.2 to 60.1) | 8 (0) | No events | 37 (10) | 26.0 (14.0 to 48.2)† |
| No | 150 (7) | 4.1 (1.9 to 8.5) | 268 (20) | 7.0 (4.5 to 10.8) | 198 (16) | 7.7 (4.7 to 12.5) ref |
| Condom use at last sexual intercourse | ||||||
| Yes | 37 (1) | 2.2 (0.3 to 15.5) | 74 (3) | 3.9 (1.3 to 12.1) | 38 (1) | 2.2 (0.3 to 15.3) |
| No | 144 (8) | 5.1 (2.5 to 10.1) | 187 (13) | 6.4 (3.7 to 11.1) | 175 (17) | 9.1 (5.6 to 14.6) |
| Symptoms (yes, past 6 months) | No is ref | No is ref | No is ref | |||
| Cystitis (urinary tract infection) | 24 (0) | No events | 41 (3) | 7.1 (2.3 to 21.9) | 40 (3) | 6.8 (2.2 to 21.0) |
| Frequent urination | 16 (0) | No events | 35 (4) | 11.6 (4.4 to 31.0) | 29 (4) | 14.1 (5.3 to 37.5) |
| Abdominal pain | 31 (3) | 8.3 (2.7 to 25.8) | 36 (0) | No events | 39 (3) | 6.8 (2.2 to 21.0) |
| Bleeding between periods | 23 (2) | 8.2 (2.1 to 32.9) | 31 (1) | 3.2 (0.4 to 22.6) | 25 (3) | 10.1 (3.3 to 31.4) |
| Bleeding after sexual intercourse | 10 (0) | No events | 11 (1) | 6.0 (0.8 to 42.5) | 15 (3) | 19.0 (6.1 to 58.8) |
| Pain during sexual intercourse | 25 (0) | No events | 24 (1) | 3.4 (0.5 to 23.8) | 27 (1) | 2.8 (0.4 to 19.8) |
| Discharge | 23 (2) | 7.2 (1.8 to 28.8) | 31 (3) | 9.7 (3.1 to 30.0) | 34 (3) | 7.7 (2.5 to 24.0) |
| None | 85 (3) | 3.3 (1.1 to 10.2) | 133 (7) | 4.9 (2.3 to 10.2) | 98(5) | 5.3 (2.2 to 12.7) |
| Recent rate of sexual partner change per 6 months* | ||||||
| No male sexual partner change | 132 (4) | 2.6 (1.0 to 7.0) ref | 171 (3) | 1.7 (0.5 to 5.3) ref | 116 (4) | 3.1 (1.1 to 8.2) ref |
| 1–3 new male sexual partners | 44 (4) | 8.1 (3.0 to 21.6) | 82 (9) | 9.1 (4.7 to 17.5)† | 93 (14) | 14.5 (8.6 to 24.5)† |
| >3 new male sexual partners | 3 (1) | 58.5 (8.2 to 415.5)† | 5 (4) | 134.0 (50.3 to 357.1)† | 5 (0) | No events |
| Partner change and condom at last sexual intercourse | ||||||
| Used a condom at last sexual intercourse, and: | ||||||
| No male sexual partner change | 22 (1) | 3.3 (0.5 to 23.4) ref | 51 (2) | 4.3 (1.1 to 17.0) ref | 22 (0) | No events |
| 1–3 new male sexual partners | 13 (0) | No events | 22 (1) | 3.5 (0.5 to 24.7) | 15 (1) | 4.0 (0.6 to 28.5) |
| >3 new male sexual partners | 1 (0) | No events | 0 (0) | No events | 1 (0) | No events |
| Did not use a condom at last sexual intercourse, and: | ||||||
| No male sexual partner change | 110 (3) | 2.5 (0.8 to 7.7) | 120 (1) | 0.8 (0.1 to 5.5) | 92 (4) | 3.7 (1.4 to 9.8) ref |
| 1–3 new male sexual partners | 31 (4) | 11.2 (4.2 to 29.8) | 60 (8) | 11.6 (5.8 to 23.3) | 78 (13) | 18.2 (10.6 to 31.3)† |
| >3 new male sexual partners | 2 (1) | 138.4 (19.5 to 982)† | 5 (4) | 162.5 (61.0 to 433)† | 4 (0) | no events |