Trends and risk factors for HIV, HCV and syphilis seroconversion among drug users in a methadone maintenance treatment programme in China: a 7-year retrospective cohort study

OBJECTIVE: This study explores the trends and associated factors of HIV, hepatitis C virus (HCV) and syphilis seroconversion among Chinese methadone maintenance treatment (MMT) clients over a follow-up period of up to 7 years. DESIGN: Drug users from 14 MMT clinics in Guangdong Province were recruited during 2006–2014. Participants were seronegative with at least one HIV, HCV or syphilis infection at baseline and had completed at least one follow-up test during the study period. We estimated HIV, HCV and syphilis seroconversion rates in follow-up years and identified the underlying predictors using a multivariate Cox regression model. RESULTS: Among 9240 participants, the overall HIV seroconversion rate was 0.20 (0.13 to 0.28)/100 person-years (pys), 20.54 (18.62 to 22.46)/100 pys for HCV and 0.77 (0.62 to 0.93)/100 pys for syphilis, over the study period. HIV seroconversion rate showed a moderate but non-significant annual decline of 13.34% (−42.48% to 30.56%) (χ(2) trend test; p=0.369), whereas the decline of HCV seroconversion was 16.12% (5.53% to 25.52%) per annum (p<0.001). Syphilis seroconversion rate remained stable (p=0.540). Urine results positive for opioid predicted HIV seroconversion (≥60% vs <60%; HR=3.40, 1.07 to 10.85), being unmarried (HR=1.59, 1.15 to 2.20), injection drug use in the past 30 days (HR=2.17, 1.42 to 3.32), having sexual intercourse in the past 3 months (HR=1.74, 1.22 to 2.47) and higher daily dosage of methadone (≥60 mL vs <60 mL; HR=1.40, 1.01 to 1.94) predicted HCV seroconversion. Being female (HR=3.56, 2.25 to 5.64) and infected with HCV at baseline (HR=2.40, 1.38 to 8.36) were associated with subsequent syphilis seroconversion. CONCLUSIONS: MMT in China has demonstrated moderate-to-good effectiveness in reducing HIV and HCV incidence but not syphilis infection among participating drug users.