Syphilis incidence rate, crude and adjusted hazards ratios for syphilis incidence among HIV-infected men who attended the national referral centre for HIV in Singapore, 2006–2017
| Characteristic | No. of incident syphilis/PYFU | Incidence per 100 PYFU (95% CI) | Univariable model | Multivariable model* | ||||
| cHR | (95% CI) | P value | aHR | (95% CI) | P value | |||
| Age at HIV diagnosis (years) | ||||||||
| 15—24 | 65/685 | 9 (7 to 12) | 3.02 | (2.00 to 4.56) | <0.0005 | 1.64 | (1.05 to 2.56) | 0.031 |
| 25—34 | 95/1304 | 7 (6 to 9) | 2.23 | (1.51 to 3.29) | <0.0005 | 1.40 | (0.92 to 2.14) | 0.118 |
| 35—44 | 71/1170 | 6 (5 to 8) | 1.84 | (1.22 to 2.76) | 0.003 | 1.35 | (0.88 to 2.06) | 0.174 |
| 45+ | 35/1125 | 3 (2 to 4) | 1.00 | Referent | 1.00 | Referent | ||
| Ethnic group | ||||||||
| Chinese | 205/3296 | 6 (5 to 7) | 3.11 | (0.97 to 3.11) | 0.064 | 1.82 | (1.01 to 3.29) | 0.046 |
| Malay | 49/659 | 7 (6 to 10) | 4.00 | (1.13 to 4.00) | 0.020 | 1.85 | (0.97 to 3.52) | 0.063 |
| Indian and others | 12/330 | 4 (2 to 6) | 1.00 | Referent | 1.00 | Referent | ||
| Marital status | ||||||||
| Single | 188/2759 | 7 (6 to 8) | 1.00 | Referent | ||||
| Ever married | 22/983 | 2 (1 to 3) | 0.34 | (0.22 to 0.52) | <0.0005 | |||
| Unknown | 56/543 | 10 (8 to 13) | 1.56 | (1.16 to 2.10) | 0.004 | |||
| HIV transmission risk group | ||||||||
| Heterosexual | 34/1533 | 2 (2 to 3) | 1.00 | Referent | 1.00 | Referent | ||
| MSM | 223/2477 | 9 (8 to 10) | 4.16 | (2.90 to 5.97) | <0.0005 | 3.29 | (2.22 to 4.87) | <0.0005 |
| IDU | 1/21 | 5 (0 to 27) | 1.96 | (0.27 to 14.31) | 0.509 | 2.15 | (0.28 to 16.24) | 0.459 |
| Sexual and IDU | 4/135 | 3 (1 to 8) | 1.36 | (0.48 to 3.84) | 0.560 | 1.48 | (0.52 to 4.20) | 0.464 |
| Others and unknown | 4/117 | 3 (1 to 9) | 1.43 | (0.51 to 4.04) | 0.498 | 1.44 | (0.51 to 4.07) | 0.492 |
| Period of HIV diagnosis | ||||||||
| 2006–2008 | 72/1714 | 4 (3 to 5) | 1.00 | Referent | 1.00 | Referent | ||
| 2009–2011 | 100/1623 | 6 (5 to 7) | 2.01 | (1.45 to 2.79) | <0.0005 | 1.96 | (1.41 to 2.74) | <0.0005 |
| 2012–2014 | 72/797 | 9 (7 to 11) | 4.13 | (2.83 to 6.02) | <0.0005 | 3.96 | (2.68 to 5.83) | <0.0005 |
| 2015–2017 | 22/150 | 15 (9 to 22) | 9.38 | (5.39 to 16.32) | <0.0005 | 7.94 | (4.52 to 13.95) | <0.0005 |
| Prior AIDS diagnosis | ||||||||
| No | 209/3368 | 6 (5 to 7) | 1.00 | Referent | ||||
| Yes | 57/917 | 6 (5 to 8) | 1.00 | (0.75 to 1.35) | 0.976 | |||
| Ever on ART | ||||||||
| Yes | 262/4249 | 6 (5 to 7) | 1.00 | Referent | ||||
| No | 4/35 | 11 (3 to 29) | 2.42 | (0.90 to 6.54) | 0.081 | |||
*Adjusted for age at HIV diagnosis, ethnic group, HIV transmission risk group and period of HIV diagnosis. Significant associations in the multivariable model were highlighted in bold.
IDU, intravenous drug use; PYFU, person-years of follow-up; aHR, adjusted HR; cHR, crude HR.