Participants, Chlamydia trachomatis positivity and unadjusted univariate risk ratios by demographic characteristics and behaviours (n=2 814)
| Covariate | Total study population N (%) | Positive for Chlamydia trachomatis n (n/N, %) | Crude risk ratio (95% CI) | p Value* |
|---|---|---|---|---|
| Demographic background | ||||
| Gender | ||||
| Women | 1378 (49) | 122 (8.9) | 0.70 (0.57 to 0.87) | 0.002 |
| Men | 1436 (51) | 181 (12.6) | 1.00 | |
| Age group | ||||
| 20–24 | 832 (29.6) | 114 (13.7) | 1.49 (0.97 to 2.28) | 0.065 |
| 25–29 | 1209 (42.9) | 115 (9.5) | 1.03 (0.67 to 1.58) | 1.000 |
| 30–34 | 523 (18.6) | 51 (9.8) | 1.06 (0.66 to 1.69) | 0.896 |
| 35–40 | 250 (8.9) | 23 (9.2) | 1.00 | |
| Marital status | ||||
| Married and cohabitation | 319 (11.3) | 29 (9.1) | 1.00 | |
| Living apart | 395 (14.1) | 41 (10.4) | 1.14 (0.73 to 1.79) | 0.614 |
| Single | 1895 (67.3) | 210 (11.1) | 1.22 (0.84 to 1.76) | 0.330 |
| Other | 187 (6.6) | 22 (11.8) | 1.29 (0.77 to 2.19) | 0.360 |
| Missing information | 18 (0.6) | 1 (5.6) | 0.61 (0.09 to 4.24) | 1.000 |
| Occupation | ||||
| Employed | 1925 (68.4) | 222 (11.5) | 1.16 (0.67 to 2.02) | 0.661 |
| Students | 761 (27) | 67 (8.8) | 0.89 (0.50 to 1.59) | 0.731 |
| Others | 121 (4.4) | 12 (9.9) | 1.00 | |
| Missing information | 7 (0.2) | 2 (28.6) | 2.88 (0.79 to 10.45) | 0.170 |
| Having children | ||||
| Yes | 204 (7.3) | 27 (13.2) | 1.25 (0.86 to 1.80) | 0.242 |
| No | 2601 (92.4) | 276 (10.6) | 1.00 | |
| Missing information | 9 (0.3) | 0 | − | − |
| Testing for and having had STIs | ||||
| Reason for current chlamydia testing | ||||
| Casual sex/check-up | 1828 (64.9) | 93 (5.1) | 1.00 | |
| Contact with chlamydia case | 461 (16.4) | 127 (27.6) | 5.41 (4.23 to 6.93) | <0.001 |
| Symptoms | 486 (17.3) | 81 (16.7) | 3.28 (2.47 to 4.34) | <0.001 |
| Other reason | 28 (1.0) | 0 | − | − |
| Missing information | 11 (0.4) | 2 (18.2) | 3.42 (0.58 to 20.13) | 0.264 |
| Presenting symptoms at clinic visit | ||||
| Yes | 601 (21.4) | 93 (15.5) | 1.62 (1.29 to 2.03) | <0.001 |
| No | 2189 (77.8) | 209 (9.6) | 1.00 | |
| Missing information | 24 (0.8) | 1 (4.2) | 0.44 (0.06 to 2.99) | 0.722 |
| Chlamydia testing (lifetime) | ||||
| Never | 453 (16.1) | 59 (13.0) | 1.00 | |
| <4 times | 1737 (61.7) | 191 (11.0) | 0.84 (0.64 to 1.11) | 0.245 |
| ≥4 times | 573 (20.4) | 49 (8.6) | 0.66 (0.46 to 0.94) | 0.024 |
| Don't remember | 41 (1.5) | 4 (9.8) | 0.75 (0.29 to 1.96) | 0.806 |
| Missing information | 10 (0.3) | 0 | − | − |
| HIV testing (lifetime) | ||||
| Never | 1062 (37.7) | 147 (13.8) | 1.00 | |
| <4 times | 1498 (53.2) | 139 (9.3) | 0.67 (0.54 to 0.83) | <0.001 |
| ≥4 times | 178 (6.3) | 7 (3.9) | 0.28 (0.14 to 0.60) | <0.001 |
| Don't remember | 63 (2.2) | 10 (15.9) | 1.15 (0.64 to 2.06) | 0.707 |
| Missing information | 13 (0.5) | 0 | − | − |
| Chlamydia testing (past 12 months) | ||||
| Yes | 1209 (42.9) | 115 (9.5) | 0.83 (0.65 to 1.05) | 0.124 |
| No | 1176 (41.8) | 135 (11.5) | 1.00 | |
| Don't remember | 87 (3.1) | 11 (12.6) | 1.10 (0.62 to 1.96) | 0.728 |
| Missing information | 342 (12.2) | 42 (12.3) | 1.07 (0.77 to 1.48) | 0.702 |
| Chlamydia infection (lifetime) | ||||
| Never | 1517 (53.9) | 141 (9.3) | 1.00 | |
| <4 times | 876 (31.1) | 105 (12.0) | 1.29 (1.02 to 1.64) | 0.043 |
| ≥4 times | 13 (0.5) | 3 (23.1) | 2.48 (0.91 to 6.78) | 0.116 |
| Don't remember | 56 (2.0) | 8 (14.3) | 1.54 (0.79 to 2.98) | 0.239 |
| Missing information | 352 (12.5) | 46 (13.1) | 1.41 (1.03 to 1.92) | 0.038 |
| Chlamydia infection (past 12 months) | ||||
| Yes | 254 (19.6) | 32 (12.6) | 1.06 (0.72 to 1.55) | 0.821 |
| No | 670 (51.7) | 80 (11.9) | 1.00 | |
| Don't remember | 26 (2.0) | 6 (23.1) | 1.93 (1.93 to 4.02) | 0.119 |
| Missing information | 347 (26.7) | 44 (12.7) | 1.06 (0.75 to 1.50) | 0.762 |
| Not applicable due to reporting never having chlamydia infection | 1517 | − | − | − |
| Any STI except chlamydia (lifetime) | ||||
| No | 1628 (57.8) | 167 (10.3) | 1.00 | |
| Yes | 609 (21.6) | 70 (11.5) | 1.12 (0.86 to 1.46) | 0.397 |
| Do not know | 506 (18.0) | 58 (11.5) | 1.12 (0.84 to 1.48) | 0.456 |
| Missing information | 71 (2.5) | 8 (11.3) | 1.10 (0.56 to 2.14) | 0.693 |
| Sexual experiences/behaviour | ||||
| Current steady relationship | ||||
| Yes | 1012 (36.0) | 104 (10.3) | 1.00 | |
| No | 1442 (51.3) | 161 (11.2) | 0.92 (0.73 to 1.16) | 0.509 |
| Missing information | 360 (12.7) | 38 (10.6) | 0.95 (0.68 to 1.32) | 0.779 |
| Concurrent sexual contacts (past 12 months) | ||||
| Yes | 587 (42.8) | 73 (12.4) | 1.37 (0.96 to 1.95) | 0.094 |
| No | 485 (35.4) | 44 (9.1) | 1.00 | |
| Missing information | 300 (21.8) | 25 (8.3) | 0.92 (0.57 to 1.47) | 0.796 |
| Not applicable due to reporting no current steady relationship | 1442 | − | − | − |
| Number of sexual partners (past 12 months) | ||||
| 0–2 partners | 622 (22.1) | 63 (10.1) | 1.00 | |
| 3–5 partners | 1141 (40.6) | 112 (9.8) | 0.97 (0.72 to 1.30) | 0.868 |
| 6–10 partner | 618 (22.0) | 79 (12.8) | 1.26 (0.92 to 1.72) | 0.154 |
| ≥11 partners | 461 (5.7) | 25 (15.5) | 1.53 (1.00 to 2.36) | 0.068 |
| Missing information | 272 (9.7) | 24 (8.8) | 0.87 (0.56 to 1.36) | 0.624 |
| Number of casual sexual partners (past 12 months) | ||||
| 0 partners | 375 (13.3) | 35 (9.3) | 1.00 | |
| 1–2 partners | 991 (35.2) | 101 (10.2) | 1.09 (0.76 to 1.57) | 0.686 |
| 3–5 partners | 691 (24.6) | 70 (10.1) | 1.09 (0.74 to 1.60) | 0.747 |
| 6–10 partner | 300 (10.7) | 42 (14.0) | 1.50 (0.98 to 2.29) | 0.067 |
| ≥11 partners | 93 (3.3) | 15 (16.1) | 1.73 (0.99 to 3.03) | 0.063 |
| Missing information | 364 (12.9) | 40 (11.0) | 1.18 (0.77 to 1.81) | 0.467 |
| Time since the last sexual contact | ||||
| Past 7 days | 1313 (46.6) | 117 (8.9) | 0.71 (0.51 to 0.97) | 0.037 |
| 1–4 weeks | 997 (35.4) | 126 (12.6) | 1.00 (0.73 to 1.37) | 1.000 |
| 1–3 months | 372 (13.2) | 47 (12.6) | 1.00 | |
| ≥4 months | 107 (3.8) | 8 (7.5) | 0.59 (0.29 to 1.21) | 0.169 |
| Don't remember | 9 (0.3) | 1 (11.1) | 0.88 (0.14 to 5.69) | 1.000 |
| Missing information | 16 (0.6) | 4 (25.0) | 1.98 (0.81 to 4.82) | 0.145 |
| Type of last sexual partner | ||||
| Steady partner | 824 (29.3) | 84 (10.2) | 1.00 | |
| Recurrent partner | 752 (26.7) | 76 (10.1) | 0.99 (0.74 to 1.33) | 1.000 |
| Casual unknown partner | 285 (10.1) | 27 (9.5) | 0.93 (0.62 to 1.40) | 0.819 |
| Casual known partner | 279 (9.9) | 32 (11.5) | 1.13 (0.77 to 1.65) | 0.573 |
| Other type | 227 (8.1) | 27 (11.9) | 1.17 (0.78 to 1.75) | 0.465 |
| Missing information | 447 (15.9) | 57 (12.7) | 1.25 (0.91 to 1.72) | 0.190 |
| Type of last sexual contact | ||||
| Vaginal and oral and petting | 880 (31.3) | 95 (10.8) | 1.00 | |
| Vaginal | 609 (21.6) | 69 (11.3) | 1.05 (0.78 to 1.41) | 0.801 |
| Vaginal and oral | 426 (15.2) | 35 (8.2) | 0.76 (0.53 to 1.10) | 0.167 |
| Vaginal and petting | 230 (8.2) | 16 (6.9) | 0.64 (0.39 to 1.07) | 0.108 |
| Vaginal and oral and petting and anal | 98 (3.5) | 19 (19.4) | 1.80 (1.15 to 2.81) | 0.019 |
| Other type of sex | 218 (7.8) | 22 (10.1) | 0.93 (0.60 to 1.45) | 0.902 |
| Missing information | 353 (12.5) | 47 (13.3) | 1.23 (0.89 to 1.71) | 0.236 |
| Condom use with new/casual partners | ||||
| Never or seldom | 843 (30.0) | 105 (12.5) | 1.00 | |
| Often or always | 1956 (69.5) | 197 (10.1) | 0.81 (0.65 to 1.01) | 0.063 |
| Missing information | 15 (0.5) | 1 (6.7) | 0.54 (0.08 to 3.59) | 1.000 |
| Taking responsibility for obtaining condom | ||||
| Never or often not | 562 (20.0) | 65 (11.6) | 1.00 | |
| Sometimes | 1288 (45.8) | 151 (11.7) | 1.01 (0.77 to 1.33) | 1.000 |
| Always | 951 (33.8) | 84 (8.8) | 0.76 (0.56 to 1.04) | 0.090 |
| Missing information | 13 (0.5) | 3 (23.1) | 2.00 (0.72 to 5.52) | 0.191 |
| Substance use | ||||
| Alcohol use before having sex (past 6 months) | ||||
| No | 243 (8.6) | 16 (6.6) | 1.00 | |
| Sometimes | 845 (30.0) | 91 (10.8) | 1.64 (0.98 to 2.73) | 0.066 |
| Several times | 1689 (60.0) | 194 (11.5) | 1.74 (1.07 to 2.85) | 0.020 |
| Don't remember | 24 (0.8) | 1 (4.2) | 0.63 (0.09 to 4.57) | 1.000 |
| Missing information | 13 (0.5) | 1 (7.7) | 1.17 (0.17 to 8.14) | 0.600 |
| Alcohol impact on taking higher sexual risks than expected by respondent (n=2534)† | ||||
| No impact | 525 (20.7) | 55 (10.5) | 0.83 (0.60 to 1.17) | 0.292 |
| Little impact | 533 (21.0) | 67 (12.6) | 1.00 | |
| Some impact | 1013 (40.0) | 107 (10.6) | 0.84 (0.63 to 1.12) | 0.237 |
| Big impact | 438 (17.3) | 51 (11.6) | 0.93 (0.66 to 1.30) | 0.694 |
| Don't remember | 15 (0.6) | 3 (20.0) | 1.59 (0.56 to 4.49) | 0.423 |
| Missing information | 10 (0.4) | 2 (20.0) | 1.59 (0.45 to 5.61) | 0.370 |
| Drug use before having sex (past 6 months) | ||||
| No | 2510 (89.2) | 268 (10.7) | 1.00 | |
| Sometimes | 203 (7.2) | 21 (10.3) | 0.97 (0.64 to 1.48) | 1.000 |
| Several times | 65 (2.3) | 10 (15.4) | 1.44 (0.81 to 2.58) | 0.224 |
| Don't remember | 9 (0.3) | 1 (11.1) | 1.04 (0.16 to 6.63) | 1.000 |
| Missing information | 27 (1.0) | 3 (11.1) | 1.04 (0.36 to 3.04) | 0.762 |
| Drug impact on taking higher sexual risks than expected by respondent (n=268)† | ||||
| No impact | 122 (45.5) | 15 (12.3) | 1.07 (0.44 to 2.59) | 1.000 |
| Little impact | 52 (19.4) | 6 (11.5) | 1.00 | |
| Some impact | 56 (20.1) | 7 (12.5) | 1.08 (0.39 to 3.01) | 1.000 |
| Big impact | 34 (12.7) | 3 (8.8) | 0.76 (0.20 to 2.85) | 1.000 |
| Don't remember | 2 (0.8) | 0 | − | − |
| Missing information | 2 (0.8) | 0 | − | − |
| Gender-specific covariates for men only (n=1436): | ||||
| Have ever got a woman unintentionally pregnant | ||||
| No | 896 (62.4) | 102 (11.4) | 1.00 | |
| At least once | 427 (29.7) | 66 (15.5) | 1.36 (1.02 to 1.81) | 0.042 |
| Don't remember | 87 (6.1) | 11 (12.6) | 1.11 (0.62 to 1.99) | 0.725 |
| Missing information | 26 (1.8) | 2 (7.7) | 0.68 (0.18 to 2.59) | 0.759 |
| For women only (n=1378): | ||||
| Current contraception method | ||||
| No birth control | 16 (1.2) | 1 (6.3) | 1.00 | |
| Any hormonal contraception | 419 (30.4) | 40 (9.5) | 1.53 (0.22 to 10.42) | 1.000 |
| Barrier method | 409 (29.7) | 34 (8.3) | 1.33 (0.19 to 9.12) | 1.000 |
| Calendar method | 308 (22.4) | 28 (9.1) | 1.45 (0.21 to 10.02) | 1.000 |
| Wish pregnancy, no contraception | 170 (12.3) | 14 (8.2) | 1.32 (0.19 to 9.38) | 1.000 |
| Sterilisation | 4 (0.3) | 1 (25.0) | 4.00 (0.31 to 51.03) | 0.368 |
| Missing information | 52 (3.8) | 4 (7.7) | 1.23 (0.15 to 10.24) | 1.000 |
| Use of emergency contraceptive pills (lifetime) | ||||
| No | 413 (29.5) | 43 (10.4) | 1.00 | |
| At least once | 944 (69.0) | 77 (8.2) | 0.78 (0.55 to 1.12) | 0.178 |
| Missing information | 21 (1.5) | 2 (9.5) | 0.91 (0.24 to 3.52) | 1.000 |
| Did abortion (lifetime) | ||||
| No | 971 (70.5) | 89 (9.2) | 1.00 | |
| At least once | 378 (27.4) | 30 (7.9) | 0.87 (0.58 to 1.29) | 0.522 |
| Missing information | 29 (2.1) | 3 (10.3) | 1.13 (0.38 to 3.36) | 0.744 |
*p Value for the crude risk ratio estimate from a likelihood ratio test.
†Follow-up question, if answered previous question.
STI, sexually transmitted infection.