| BackgroundThe main factor associated with HIV and other blood-borne transmitted diseases is the multi-person re-use or sharing of syringes and needles. In addition, the indirect sharing of equipment such as water, cotton, cookers and other drug preparation equipment has been attributed to assisting HIV transmission. Particularly where IDUs sell sex to help fund their drug use, injecting drug users (IDUs) are also vulnerable to HIV infection through sexual transmission. They are also at high risk from other blood-borne and sexual-transmitted infections such as hepatitis B and C, and syphilis. Because of a large population base, a small increase of HIV prevalence in the general population in China would mean a large increase in the number of domestic infections and a significant contribution to the total number of infections around the world. The traditional approach to identify risk factors for HIV infection among IDUs is to conduct cross-sectional survey in a defined area. However, a more definitive approach to identify risk factors for HIV infection is to assemble a cohort of initially uninfected individuals who are then followed prospectively at prescribed time intervals for seroconversion. This design, the seroincidence cohort, overcomes the major limitation of the cross-sectional seroprevalence study by establishing a temporal causal relationship between expose and disease occurrence measured by seroconversion. Several cohort studies have been conducted among IDUs in China, most in the provinces of Yunnan and Guangxi, which have a high HIV prevalence. These studies showed varying but generally high seroconversion rates. China has a large geographic area and a variety of cultures and customs; more cohort studies among IDUs should provide valuable data for understanding the whole picture of the HIV epidemic. In addition, recently, with the development of prevention and treatment such as methadone maintenance treatment (MMT), needle exchange and HIV voluntary counseling and testing, the prospective cohort study is needed to conduct among IDUs in order to obtain the new data.Objective1. To investigate cohort retention and factors associated with Socio-demographic characteristics, drug use and sexual behaviors at the baseline among IDUs in Xichang, Sichuan Province.2. To investigate HIV, HCV, HBsAg and syphilis sero-incidence and contributed factors of the HCV/HBV infection among IDUs in a drug trafficking city of southwest Sichuan Province.3. To study trends of HIV risk behaviors in the 2-year follow-up study of IDUs in Xichang of Sichuan Province.MethodsIn April 2006, a community-based baseline survey was conducted to recruit 376 HIV-seronegative IDUs for a prospective cohort study in Xichang County of Sichuan Province, China. Follow-up visits were conducted every 6 months to investigate drug use and sexual behaviors, and blood specimens were also collected to test for HIV antibody, HCV antibody, HBsAg, and syphilis antibody. Factors associated with participants completing the 2-year follow-up on time were analyzed using chi-square test in univariate analysis and Logistic regression model in multivariate analysis. Univariate and multivariate Cox regression model were conducted to analyze factors contributed to HCV and HBsAg seroconversion. Generalized estimating equation (GEE) were used to knowledge the trends of drug use and sexual behaviors in a prospective cohort of IDUs.Result1. During the 24-month follow-up period, cohort retention rate was 83.8% (315/376). Multivariate Logistic regression model showed that factor significantly contributed to cohort retention was appearing at the 6-month follow-up visit (OR, 5.91; 95%CI, 3.18-10.96; P<0.0001).2. Total HIV seroincidence was 0.62 per 100 person-years (95% confidence interval (CI), 0.01-1.23), total syphilis seroconversion in this cohort was 4.12 per 100 person-years (95% CI, 2.4-5.84), total HCV seroconversion was 30.29 per 100 person-years (95% CI, 21.24-39.35). HBsAg incidence was 8.80 per 100 person-years (95% CI, 6.31-11.29). Multivariate Cox regression model showed that risk factors, which were significantly associated with HCV seroincidence, included≥28 years old (Relative ratio (RR), 0.34; 95% CI, 0.18-0.65; P=0.0010) and ever having shared needles and syringes in the past 3 months (RR, 4.0; 95% CI, 1.40-11.39; P=0.0095). In multivariate Cox regression model, ever exchanging sex for money in the last 6 months (RR, 2.76; 95% CI, 1.09-6.96; P=0.0319) was significantly associated with HBsAg seroconversion.3. At the baseline and the 12-month fellow-up visit, the numbers who injected drugs≥7 times/week in the past 3 months, ever shared needles and syringes in the last 3 months, ever shared needles and syringes indirectly in the last 3 months, ever shared needles and syringes with new partners in the last 3 months, ever had unprotected sex with non-primary sex partners in the last 30 days, ever exchanged sex for money in the last 6 months, ever had new sex partners in the last 6 months, ever joined the needle exchange program in the last 3 months, all decreased significantly. For these variables, there are no significant changes, at the 12-month fellow-up and the 24-month fellow-up visit. At the 12-month fellow-up and the 24-month fellow-up visit, the numbers who ever exchanged money for sex in the last 6 months, ever joined the MMT in the last 3 months, all decreased significantly.Conclusion1. The study showed that cohort retention of IDUs with no callback at 6th month was low. The retention strategies are to be reexamined and revised to increase the retention rate, and thereby minimize potential selection bias.2. The study showed that HIV seroincidence maintained at a low level, HCV, HBsAg and syphilis seroincidence was still high among IDUs in Sichuan Province, China.3. We should take the effective measures to control the incidence of HCV and HBV, especially must prevent sharing needles and syringes, and improve the publicity and education among the prostitutes.4. Our study showed that even sharing needles and syringes in the past 3 months and having unprotected sex with non-primary sex partners in the last 30 days have been declining. Future studies should be conducted to provide targeted interventions in reducing unprotected sex with a primary sex partner, and increasing attraction and retention of drug users to methadone maintenance treatment (MMT) and the needle exchange program. |
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