Methods: Articles providing information on the mean duration of infection and the prevalence of cirrhosis for those infected with HCV through injection drug use were retrieved. A fixed effects meta-analysis was performed. Information in the articles regarding co-variates such as age, sex, HIV infection, alcohol abuse, ALT levels and study population (liver clinic versus addiction therapy) were abstracted. For a subset of studies with information on all co-variates, a fixed effects meta-regression was conducted. Each analysis was based on a Poisson regression model and analyzed using Markov Chain Monte Carlo techniques with Gibbs sampling. Uninformative prior distributions were used.
Results: A total of ten articles met the inclusion and exclusion criteria. The estimated rate of progression to cirrhosis resulting from fixed effects meta-analysis was 5.1 per 1000 person-years with a 95% credible region (CR) of 4.5 to 5.6 per 1000 person-years. A subset of six studies provided information on all six co-variates. The estimated rate of progression to cirrhosis for these six studies was 1.6 per 1000 person-years (95% CR 0.6 to 3.4 per 1000 person-years). The study population type was the most important factor in estimating the risk of progression to cirrhosis, with estimates derived from liver clinic studies having a 12-fold higher progression rate compared to studies that were community-based.
Conclusions: Rates of progression to cirrhosis for those who obtained HCV infection through injection drug use are comparable to non-IDU populations. HCV prognosis depends on the study population - individuals that present to liver clinics may have faster rates of progression than those identified through addiction therapy. Unlike the non-IDU population, co-variates such as HIV infection and abuse of alcohol appear to have no effect on progression rates.