In this large multi-site study of young IDUs, self-report detected only 28% of all anti-HCV-positive injectors. Self-reported anti-HCV negativity correctly identified a little more than half of all anti-HCV-negative participants. These findings were nearly identical to a Denver, Colorado, study reporting that only 29% of anti-HCV-positive IDUs believed they were positive.15
Clearly, such a low level of detection of an endemic disease in a population suggests that improved access to HCV testing and education is needed, particularly as medical monitoring and treatment of HCV infection may have substantial health benefits.28
In another large study of IDUs, a much higher proportion of HIV-positive participants (44%) correctly reported their HIV-status.29
We also found substantial geographic differences in awareness of HCV serostatus, with higher proportions of both anti-HCV-negative and positive participants in New York and Seattle knowing their HCV serostatus. It is conceivable that there are regional differences in access to HCV screening and in the proportion of patients returning for test results; there may also be geographic differences in the quality of pre- and post-test counseling available.
In our study, previous enrollment in drug treatment or the use of needle exchange were both associated with awareness of HCV serostatus; this suggests that these programs may contribute to case-finding and HCV prevention education. A small study of IDUs in methadone treatment in London (n
=90) found that 77% of anti-HCV-positive IDUs were aware of their serostatus.30
A survey of U.S. drug treatment programs reported that 76% of methadone programs do provide onsite HCV antibody testing to their clients,31
and a national survey of needle exchange programs in the U.S. found that 43% of programs do offer HCV antibody testing. (Personal communication, D.C. Des Jarlais, 2005). We found no association between HCV awareness and history of incarceration. A recent study reported an increase in universal or targeted HCV screening programs in U.S. state prisons,32
which may contribute to a net increase in access to testing for drug injectors. The quality and content of HCV counseling and education in screening programs in these settings may vary substantially; efforts to standardize and improve HCV-screening protocols may be warranted.
The association between self-reported HCV serostatus and risk behavior in this population varied in relation to whether participants were anti-HCV-positive or negative. Among anti-HCV-positive IDUs, those who knew their serostatus were no less likely than other anti-HCV-positive IDUs to report injection practices that may transmit infection. Similar results have been found in other studies. In the Denver study, there was no association between knowledge of anti-HCV-positive serostatus and distributive syringe sharing, although fewer who were aware of their serostatus reported sharing drug preparation equipment.17
A longitudinal study of young IDUs reported that those who received an anti-HCV-positive test result were no more likely to change risk behavior than those who believed they were anti-HCV-negative; overall, 20% of participants reduced their risk behavior after learning the results of their HCV antibody test.19
A relatively high proportion of anti-HCV-positive participants in that study also reported heavy alcohol use (48%), and no change in frequency of use was noted. However, the sample size was relatively small, and follow-up retention was relatively low (<50%); thus, it remains unclear whether awareness of serostatus may be sufficient to change behavior that may transmit HCV or worsen progression of disease among anti-HCV-positive injectors.
Awareness of anti-HCV negativity appeared to benefit young IDUs in this study in reducing exposure risk, as they were significantly less likely than those who did not know their anti-HCV serostatus to inject with a syringe previously used by another injector or share filtration cotton. An association between awareness of anti-HCV negativity and risk behavior has not been reported previously; these findings would support expansion of HCV testing for the purpose of identifying and counseling anti-HCV-negative injectors.
Limitations should be considered before drawing conclusions from this study. Awareness of HCV serostatus was associated with a history of drug treatment and longer duration of drug injection—characteristics that may indicate more problematic drug use. This difference could have led to confounding in the association between awareness of one's status and other characteristics. However, adjustment for duration of injection in estimating the association between knowledge of anti-HCV serostatus and risk behavior did not change the odds ratio to a meaningful degree. This study did not collect information on known or perceived HCV serostatus of the IDUs' injection partners, and we were unable to discern whether anti-HCV-positive IDUs injected in a different manner when they were with anti-HCV-negative IDUs. This limitation applied to previous studies that found little benefit from counseling and education on reducing risk among anti-HCV-positive IDUs.17,19
However, this study and previous studies do suggest that HCV counseling and education protocols could be improved with increased emphasis on the importance of reducing transmission risk behavior. In fairness to the providers of HCV counseling and testing evaluated in these studies, standardized protocols have only recently been developed in the U.S.,23
and scientific knowledge regarding specific transmission risk behavior was relatively uncertain for many years after HCV was identified. A recent qualitative study of IDUs in London—one third of whom were anti-HCV-positive—noted that many reported confusion and uncertainty regarding HCV risk, and that, in addition, HCV was perceived as an almost inevitable consequence of drug injection.33
As mentioned, we were not able to discern whether HCV seroconcordance among injection partners mitigated the potential for HCV transmission suggested by risk behavior among anti-HCV-positive IDUs. It was also not possible to identify specific weaknesses in any previous HCV counseling and education our participants received. Another limitation was the cross-sectional design of this study, which limits the attribution of risk behavior to prior awareness of HCV serostatus, since we cannot be certain that testing occurred more than three months prior to study enrollment. It is also conceivable that there was measurement error such that self-reported risk behavior did not conform precisely to the three-month period of interest. However, the short span of the referent period would tend to increase the accuracy of self-report, and would also make it less likely that a meaningful proportion of HCV tests were performed and results given during that time period. A further limitation is that we cannot determine whether motivation to be tested is associated with risk avoidance; all observational studies of screening programs suffer from this limitation and a randomized controlled trial of HCV screening is unlikely.
Several implications can be drawn from this analysis. Clearly, there is a great need to expand access to screening and counseling in this high prevalence population, as 72% of anti-HCV-positive and 46% of anti-HCV-negative IDUs did not know their antibody status. HCV testing and education may provide knowledge and motivation for anti-HCV-negative IDUs to continue safe injection practices or reduce their injection frequency. HCV education and counseling for anti-HCV-positive IDUs should stress the importance of their role in reducing HCV transmission and encourage the avoidance of alcohol to maintain their health. We could not examine the most important potential benefit of case-finding for anti-HCV-positive IDUs, which is to facilitate access to medical monitoring and treatment of HCV infection. However, a cost-effectiveness study of HCV screening in the general population showed that the cost per case detected was substantially lower ($1,246 per case) than the cost of other accepted public health screening programs such as fecal occult blood ($4,000) and pap smears ($5,000).13
Using a pre-screening protocol that selects only individuals at risk of HCV, the estimated cost per case was reduced to $487. However, whether increased HCV case-finding in IDUs will lead to an increase in medical management and treatment of HCV remains an open question.
The U.S. Preventive Services Task Force recently issued a set of recommendations related to HCV screening; their review of published research led them to conclude that no studies had shown that “looking for HCV infection in adults who had no symptoms but were at high risk…leads to benefits.”34
The current study suggests that an important benefit of HCV screening in this high risk population may be to support maintenance of safe injection among anti-HCV-negative drug injectors. It also suggests the need for improvements in counseling for anti-HCV-positive IDUs to decrease their risk for transmitting HCV to other IDUs and for avoiding alcohol use. Thus, our findings would support HCV screening recommendations by the CDC and the National Institutes of Health Consensus Panel on Medical Management of HCV to screen users of injection drugs.35–37
One outstanding research question arising from this analysis is how to improve risk-reduction counseling for anti-HCV-positive individuals to make further gains toward reducing the HCV disease burden in this population.