METHADONE TREATMENT AS A DETERMINANT OF HIV RISK REDUCTION AMONG INJECTING DRUG-USERS - A NESTED CASE-CONTROL STUDY

In order to evaluate the protective effect of methadone treatment on H IV infection, we performed a nested case-control study on seroconverte rs (cases) who were part of a cohort of HIV-negative injecting drug us ers (IDUs) (controls). Controls were matched with cases by sex, age, d uration of drug use and follow-up time. Information on methadone treat ment in the year prior to seroconversion was collected using clinical registries. Univariate and multivariate conditional logistic regressio n were used to identify variables related to HIV-seroconversion. The s tudy included 40 cases and 40 controls. Univariate analysis showed the following variables to be associated to HIV seroconversion: number of cycles of treatment, daily dose and time out of treatment. After perf orming multivariate analysis, daily dose remained protective with a li near effect noted even at low doses and time out of treatment was the most important risk factor. The risk increased 1. 5 times for every 3 months spent out of treatment. Long-term methadone treatment protects against HIV infection. Its effect may be attributable to a reduction i n the frequency of injecting drug use or to an increased knowledge of risk factors following counselling in drug centres.