We have demonstrated several novel and important findings with respect to uptake of treatment for recently acquired HCV infection in the ATAHC study. First, treatment uptake was high among participants who were HCV RNA positive at enrolment (76%), despite the fact that 77% reported injecting and 80% of injectors reported recent injecting. Second, factors independently associated with HCV treatment included a longer estimated duration of infection and higher HCV RNA at enrolment. In those who were HCV RNA positive at baseline, a higher HCV RNA at enrolment and not having current depression were associated with HCV treatment uptake.
A high proportion of ATAHC participants, were interested and deemed clinically suitable to commence HCV treatment. In this study, the observed uptake of HCV treatment among participants with newly acquired HCV infection is much higher than studies in the setting of chronic HCV infection which range from 3–28% in clinic-based cohorts (Adeyemi et al., 2004
; Falck-Ytter et al., 2002
; Fishbein et al., 2004
; Fleming et al., 2003
; Groom et al., 2008
; Hallinan et al., 2007
; Jowett et al., 2001
; Mehta et al., 2006
; Morrill et al., 2005
; Restrepo et al., 2005
), 15–16% in community-based cohorts (Rocca et al., 2004
; Stoove et al., 2005
) and 1–6% among cohorts of injection drug users (Grebely et al., 2009
; Hall et al., 2004
; Mehta et al., 2008
; NCHECR., 2008
). Given that the majority of sites were tertiary care centres, there is likely a referral bias towards enrolling those more likely to be interested in receiving treatment, but the same can be said of clinic-based studies of chronic HCV. The high uptake of treatment is impressive given that the majority of participants were IDUs. It is also likely that the shorter duration of therapy for recently acquired infection and higher likelihood of response may have led to an increased proportion of patients interested in treatment. In one study evaluating attitudes toward treatment for HCV infection among IDUs at various treatment efficacy levels, willingness to consider treatment increased with efficacy of treatment scenarios, from 36% for 20% efficacy to 93% for 70% efficacy (Doab et al., 2005
Lower HCV treatment uptake among participants with lower HCV RNA and shorter estimated duration of infection may reflect clinician-directed treatment deferral to await spontaneous viral clearance. While the natural history of acute HCV infection is unclear with respect to predictors and time-course of viral clearance (Cox et al., 2005
; Glynn et al., 2005
; Jauncey et al., 2004
), declining HCV viral load in early infection has been associated with greater spontaneous clearance (Hofer et al., 2003
). The vast majority of individuals who spontaneously clear HCV infection do so within 8–16 weeks of infection. Other demographic and injecting characteristics had no significant impact on treatment uptake.
Among those positive for HCV RNA at baseline, a higher HCV RNA and depression were the only factors independently associated with treatment uptake. Given the neuropsychiatric side-effects of PEG-IFN, it is not surprising that those with concomitant depression were two times less likely to receive treatment.
Collectively, these data provide important insights into the clinical decision making around the initiation of treatment for recently acquired HCV infection. These data suggest that at the time of presentation, decisions about whether to initiate treatment for recently acquired HCV infection were mainly driven by clinical factors, such as the estimated duration of infection and HCV RNA levels, with treatment being delayed to enable the patient time to spontaneously clear their infection. Having concurrent depression also may have influenced the clinicians’ decision to commence therapy.
The lack of an association between HCV treatment uptake and injecting drug use has important implications. First, it suggests that IDUs have a favorable outlook on HCV treatment, consistent with other research (Doab et al., 2005
; Grebely et al., 2008
; Seal et al., 2007
; Stein et al., 2001
; Strathdee et al., 2005
; Walley et al., 2005
). Second, it appears that clinicians involved in this study did not use recent injecting drug use as an exclusion criterion for treatment. Third, it provides a foundation to evaluate treatment for recently acquired HCV infection in IDUs, which is needed given the low numbers of IDUs in previous studies of treatment for recent infection (Gerlach et al., 2003
; Jaeckel et al., 2001
; Santantonio et al., 2005
; Wiegand et al., 2006
This study has several limitations. First, the results may not be generalizable to other populations of participants with recent HCV infection. Second, the study was predominantly conducted at tertiary care centres leading to a potential selection bias; participants may have had a higher level of engagement with the health care system compared with the overall population with recent HCV infection. This potentially higher level of engagement is further amplified by the fact that participants had to be tested, identified as having recently acquired HCV and recruited into a research study in a timely fashion (Walsh et al., 2008
). Also, the clinicians who managed patients in this study may have more experience in working with IDUs and thus more comfortable and more likely to treat HCV in this subset of participants. An estimated 9,600 HCV infections are acquired annually in Australia, with 90% occurring in IDUs (Razali et al., 2007
). A minority of cases would be detected in the initial twelve months of infection, and a small proportion of diagnosed cases would be assessed for HCV treatment (Walsh et al., 2008
). Lastly, there may have been factors not measured that may have accounted for why some IDUs underwent treatment whilst others did not.
The ATAHC study has demonstrated that IDUs can be successfully recruited into a study of recent HCV infection and that a high proportion commenced HCV treatment when this was made available to them. The high rate of treatment uptake and the limited association between injecting behavioural factors and uptake indicates that both individuals with early HCV infection and their clinicians are willing to consider treatment among the predominantly IDU-acquired composition of the study population.