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Does Bleach Disinfection of Syringes Protect Against Hepatitis C Infection Among Young Adult Injection Drug Users?
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Summary. Hepatitis C virus (HCV) has emerged as a major public health problem among injection drug users. In this analysis we examine whether disinfection of syringes with bleach has a potentially protective effect on anti-HCV seroconversion. We conducted a nested case-control study comparing 78 anti-HCV seroconverters with 390 persistently anti-HCV seronegative injection drug users. These data come from the Second Collaborative Injection Drug Users Study, a prospective cohort study that recruited injection drug users from five U.S. cities between 1997 and 1999. We used conditional logistic regression to determine the effect of bleach disinfection of syringes on anti-HCV seroconversion. Participants who reported using bleach all the time had an odds ratio (OR) for anti-HCV seroconversion of 0.35 (95% confidence interval = 0.08-1.62), whereas those reporting bleach use only some of the time had an odds ratio of 0.76 (0.21-2.70), when compared with those reporting no bleach use. (Thus, risk 65% lower when reported using bleach all the time and 24% lower when reporting using bleach less than all the time). These results suggest that bleach disinfection of syringes, although not a substitute for use of sterile needles or cessation of injection, may help to prevent HCV infection among injection drug users. Epidemiology 2002; 13(6):738-741. Farzana Kapadia et al for the Second Collaborative Injection Drug User Study (CIDUS-II) Group.
Injection drug users are at an increased risk for hepatitis C virus (HCV) infection, with incidence ranging from 15% to 40% per year. Among recently initiated injection drug users, anti-HCV prevalence approaches 30-50%, and both anti-HCV prevalence and incidence exceed corresponding measures for HIV infection. Strategies to prevent transmission of these blood-borne infections include syringe disinfection with bleach because it is both inexpensive and well accepted by injection drug users. However, bleach use has been evaluated primarily for HIV prevention with findings yielding negligible effects. The fact that these findings are inconclusive has been attributed to improper bleaching techniques rather than lack of effect, given that many blood-borne pathogens are susceptible to bleach. The larger reservoir of HCV-infected persons and higher efficiency of HCV transmission compared with HIV suggest that bleach disinfection of syringes might reduce HCV infection risk, a hypothesis we evaluate in this report.
From 1997 through 1999, injection drug users were enrolled in a prospective cohort study at six sites in five U.S. cities: Baltimore, Chicago, Los Angeles, New Orleans and New York City (two distinct neighborhoods of the latter). To be eligible for enrollment, injection drug users had to be 18-30 years old or recent initiates into drug injecting (injecting [less than 5 years). To be included in this analysis, participants had to be between 18 and 30 years old and be current injection drug users (defined as having injected drugs within the 6 months preceding an interview).
Injecting practices examined in this analysis include sharing cookers used to melt drugs into a liquid, sharing cottons used to filter out particles as drugs are drawn into a syringe, sharing rinse water to clean syringes, and backloading (a practice in which one syringe is used to distribute drugs into multiple syringes). Additionally, participants reporting syringe sharing were asked to report on syringe disinfection with substances such as bleach, water, rubbing alcohol or peroxide.
Results
Prevalence of anti-HCV among the 2,198 participants enrolled in the original cohort was 36%. Follow-up and screening of participants who were seronegative at baseline (N = 1,324) identified 78 RIBA-confirmed anti-HCV seroconverters. We matched 390 controls to the 78 case participants identified. Males comprised 62% of the participants included in this analysis. Forty-six percent of participants were white, 19% were Hispanic/Latino, 27%
were black, and 8% were of another race/ethnicity. Twenty-seven percent of participants reported injecting drugs with syringes previously used by another person, 41% reported sharing cookers, 33% sharing cottons, and 30%
sharing rinse water.
Results from univariate analysis showed that anti-HCV seroconversion was more common among those reporting injecting drugs with other people (odds ratio [OR] = 2.2); injecting in a public place (OR = 2.4); and sharing cottons (OR = 1.7), cookers (OR = 1.8) and rinse water (OR = 1.7). Bleaching frequency showed a trend toward a protective effect on anti-HCV seroconversion. Compared with those reporting "never" using bleach, odds
ratios for seroconversion were 0.76 (95% confidence interval = 0.21-2.70) for participants reporting bleach use "less than all the time" and 0.35 (0.08-2.31) for those reporting using bleach "all the time" (risk is 65% lower for individuals reporting bleach use "all the time" and 24% lower for individuals reporting use of bleach "less than all the time".
DISCUSSION By Authors
Study Limitations
First, although the initial cohort was large, we had only 78 eligible seroconverters, limiting our ability to detect an association between bleach use and anti-HCV seroconversion. A sample of 108 anti-HCV seroconverters would have been necessary to detect an odds ratio of 0.5 with an alpha level of 0.05 and 80% power. Second, underreporting of syringe sharing or overreporting of bleach use attributable to socially desirable responding could attenuate the association of anti-HCV seroconversion with syringe sharing and with bleach use. However, earlier reports suggest veracity of self-reports among injection drug users. Third, assessment of the bleaching process focused only on frequency of disinfection use; contact time between the syringe and bleach, which is also important, was not ascertained.
Also, given the structure of the interview, bleach use was assessed only among individuals reporting syringe sharing. Although it may seem unnecessary to ascertain bleach use among those who do not report syringe sharing, this is an important limitation for this analysis as recent studies have shown an increased risk of HCV seroconversion among those who share cookers, cottons and rinse water and among those who may inject (knowingly or unknowingly) with previously contaminated syringes.13, 15 On the basis of this rationale, case and control participants not reporting syringe sharing were also included in this analysis to account for the risk of HCV seroconversion from indirect sharing practices; they were grouped with those who did not disinfect with bleach. With consistency of results across categorizations of bleach use, this conservative regrouping might underestimate the exposure, possibly biasing the association toward the null.
Few interventions are currently available to curb the high rates (>10 per 100 person-years) of anti-HCV seroconversion among young or newly initiated injection drug users.8 Second, conventional interventions such as syringe exchange and drug treatment programs may have less impact on HCV incidence because younger injection drug users, those more likely to seroconvert, are less likely than older users to seek services from such agencies.
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