As a leading notifiable disease and a major cause of drug related morbidity and mortality, it is well recognised that the hepatitis C virus (HCV) poses a significant public health challenge. In addition to quality of life impairment at all disease stages [1
], most individuals exposed to HCV become chronically infected (and infectious), with 10–20% developing cirrhosis or hepatocellular carcinoma [3
In many countries the majority of HCV prevalence cases are comprised of current or former injecting drug users (IDU; [4
]). Incidence data implicates a wider range of HCV transmission risk practices (e.g., environmental contamination) and injecting paraphernalia (e.g., spoon, filter, water, swab) other than the sharing of used syringes [7
Such findings, in the context of continuing high prevalence of injecting risk behaviour [6
] and HCV infection [12
], suggest that controlling the spread of HCV is dependent on preventing transmission within the IDU population [8
]. Although social and structural determinants of drug use and 'risk' are important to this end [15
], HCV transmission is unlikely to be reduced without significant changes in the specific behaviours believed responsible for the spread of the virus [16
]. Reductions in the prevalence of risk behaviours is therefore a necessary component of prevention responses and require an expansion of existing strategies through improved education and support for IDU [17
One of the challenges in HCV surveillance and prevention rests with evaluating the efficacy of the broad range of interventions designed to reduce the prevalence of high-risk practices and, ultimately, rates of HCV seroconversion. To monitor HCV incidence, evaluate intervention efficacy or clarify the significance of putative/theoretical risk practices, longitudinal cohort studies represent a gold standard of evidence. These studies, however, are expensive to conduct and difficult to complete successfully in community-based samples (and therefore less likely to be funded in some jurisdictions) because high HCV prevalence and incidence rates in IDU necessitate the serial testing of very large numbers of participants. The capacity of current surveillance mechanisms are therefore impeded in terms of their capacity to evaluate prevention initiatives and identify HCV transmission risk practices that contribute most to new infections. This not only poses a significant barrier at the level of nationwide population prevention programs, but also for the multitude of local community and agency specific HCV prevention programs.
An alternative approach to sero-incident studies that is arguably better suited to local community level HCV prevention and evaluation is to assess participation in high-risk practices for HCV transmission. Until recently, this has been complicated by the lack of a standardised instrument capable of reliably measuring participation in a sufficiently broad range of injecting and other putative risk practices associated with HCV transmission. Although some injecting risk measures [18
] demonstrate acceptable reliability and validity [20
], they have poor content validity for HCV monitoring purposes due to insufficient coverage of the full range of HCV risk practices.
The predominant mode of HCV transmission is via risky injecting drug use practices [12
]. Evidence also implicates tattoos playing a role in the spread of HCV, particularly those performed by non-professionals and/or in prison settings [23
]. Sexual transmission of HCV is highly debated [27
]. Although some methodologically suspect studies have suggested an 'appreciable' risk of sexually transmitted HCV [29
], recent prospective cohort studies with considerable person-years of follow-up have concluded the risk to be extremely low and perhaps non-existent [30
]. The risk of horizontal household transmission of HCV is also suggested to be similarly low [32
The Blood-Borne Virus Transmission Risk Assessment Questionnaire (BBV-TRAQ)
is a standardised content and construct valid instrument offering comprehensive assessment of injecting, sex and skin penetration risk practices for HCV, HBV, and HIV [34
] and has been translated by the World Health Organisation into eight languages [36
]. Although the comprehensive nature of the risk practices canvassed in the BBV-TRAQ is an advantage, each of these practices ultimately contribute equally to BBV-TRAQ scores, despite evidence suggesting they carry markedly different relative risks of transmitting a blood-borne virus (BBV).
This limitation makes it difficult for the current format BBV-TRAQ to offer a genuine and practical indication of the risk of contracting a BBV. This paper reports on the application of a weighting scheme for BBV-TRAQ items to take account of the relative risks associated with different risk practices. The analyses undertaken in this paper focus on HCV by providing initial normative data of HCV transmission risk among a sample of IDU, and explores the properties of the weighted scale to approximate overall HCV transmission risk in this group. IDU constitute the main HCV sero-prevalent and sero-incident risk group in many countries and constitute the population from which the BBV-TRAQ was originally developed. Thus this population was a logical choice from which to begin the iterative process of scale refinement described in this paper.