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.