The authors respond:
We thank Hagan et al1 for presenting their data on injection drug users (IDUs) to further examine the association of bleach disinfection of needles and syringes with hepatitis C virus (HCV) seroconversion. The authors attempted to replicate the findings in our study by using a similar method and approach toward their data. They reported an elevated odds of HCV infection among IDUs who used bleach “all of the time” versus “less than all the time,” which contrasts with our earlier report showing decreased odds of HCV seroconversion.1,2
Although we acknowledge that the analyses were inconclusive and that bleach as used in field circumstances might not be fully effective, the biologic plausibility of Hagan and colleagues’ findings is difficult to understand. We would not expect bleach use to increase the risk of seroconversion, and indirect pathways are not immediately obvious. We suspect that the elevated risk might be a function of residual confounding resulting from other risk factors unaccounted for in their analysis. Adjusting for potentially confounding factors that were identified in our study might be insufficient. This possibility cannot be excluded as they have noted the baseline prevalence of HCV was considerably higher in the Seattle study than in our multisite data (83% vs. 36%). This comparison suggests that IDUs in Seattle might be engaging in riskier drug preparation practices that might be less likely to be affected by bleach disinfection of syringes but that could place them at a higher risk of HCV seroconversion. For example, the most common form of heroin in Seattle is “black tar,”3 the use of which has been associated with rapid vascular scarring and increased difficulty by IDUs to effectively hit a vein. Repeated failed attempts to find a vein with the needle results in gross contamination of skin, injection equipment, and environmental surfaces with the IDU’s blood, which, if contaminated with HCV, could infect other injection partners.
In the face of contradictory results, we further examined this association by using data from the ALIVE study, a longitudinal cohort study of injection drug users in Baltimore described in detail elsewhere.4 We performed a nested case-control analysis similar to that described in our article. We identified 25 HCV seroconverter cases and 114 uninfected control subjects who were all recently active injection drug users; controls were matched to cases for race, date of entry into the study (± 1 y), duration of follow up, and cocaine injection. Among the 25 cases and 114 control subjects included in this analysis, the unadjusted odds ratio for HCV seroconversion for bleach use “all the time” versus “less than all the time” was 0.53 (95% confidence interval = 0.12–2.39).
Given the inconclusive results for each of these analyses, it is fair to say that understanding the relationship between bleach disinfection of syringes and HCV seroconversion will require additional laboratory and field studies, specifically studies with sufficient power and appropriate measures of confounding variables to better understand this association. We invite collaboration with Dr. Hagan and other investigators to construct a combined analysis to further clarify this association, and we suggest that a controlled trial might be warranted to examine whether syringe disinfection with bleach might be a useful adjunct to a bloodborne infection prevention program.
Center for Urban
New York Academy of Medicine
1216 Fifth Avenue, Room 556
New York, NY 10029
Richard S. Garfein
Division of HIV/AIDS Prevention
National Center for HIV/STD/TB
Prevention Centers for Disease Control and Prevention
Center for Urban Epidemiologic Studies
New York Academy of Medicine
New York, NY
1.Hagan H, Thiede H, Des Jarlais DC. Does bleach disinfection of syringes have any effect on hepatitis C virus infection among injection drug users? [Letter]. Epidemiology
2.Kapadia F, Vlahov D, Des Jarlais DC, et al. Does bleach disinfection of syringes protect against hepatitis C infection among young adult injection drug users? Epidemiology
3.National Drug Intelligence Center. Washington Drug Threat Assessment (Department of Justice NIDC website). February 2003. Available at:http://www.usdoj.gov/ndic/pubs3/3138/heroin.htm
. Accessed July 1, 2003.
4.Vlahov D, Anthony JC, Munoz A, et al. The ALIVE study, a longitudinal study of HIV-1 infection in intravenous drug users: description of methods and characteristics of participants. NIDA Res Monogr