Risk factors and predictors of human immunodeficiency virus infection among injection drug users

Background/Aim: Injection drug users (IDUs) have a high risk of acquiring an infection with the human immunodeficiency virus (HIV). To improve counseling and prevention, a better understanding of risk factors and predictors for an infection must be gained. This retrospective study has the aim to determine the risk factors for acquisition of HIV infection other than sharing of needles/ syringes. Methods: The study population consisted of all patients admitted to the detoxification unit between 1991 and 1996 who met ICD-10 criteria for opioid dependency, who reported to share needles, and who agreed to have an antibody test. Possible risk factors were assessed by interview. Cross tables based on bivariate logistic regression were constructed to estimate the relative odds. Multiple logistic regression modeling procedures were used to adjust possible confounding factors. Results: A total of 1,049 out of 1,656 patients admitted were included into the study. 4.8% of the patients were HIV-1 seropositive. The prevalence was higher among older patients and among patients living with a significant other substance drug user with substance dependency, after a longer duration of drug use, and after coinfection with hepatitis B virus and/or hepatitis C virus (HCV). Using multiple logistic regression analyses and including all individually significant risk factors, we found only coinfection with HCV to remain significant. 92% of the HIV-infected patients were also HCV infected. In the group younger than 23 years of age, a total of 53.5% of the IDUs were still seronegative for HIV, hepatitis A and B virus, and HCV. Conclusions: Despite the high rate of HCV coinfection ( 92%) in HIV-infected patients, we found more than 50% of IDUs younger than 23 years to be neither infected with HCV nor with HIV. Early prevention strategies against infectious diseases should especially focus on young IDUs.