Meta-regression of hepatitis C virus infection in relation to time since onset of illicit drug injection: the influence of time and place

Abstract

The authors examined the relation between time since onset of illicit drug injection (time at risk) and rates of hepatitis C virus (HCV) infection by using meta-regression. In 72 prevalence studies, median time since onset of injection was 7.24 years and median prevalence was 66.02%. The model showed statistically significant linear and quadratic effects of time at risk on HCV prevalence and significantly higher prevalence in developing and transitional countries and in earlier samples (1985-1995). In developed countries post-1995, mean fitted prevalence was 32.02% (95% confidence interval: 25.31, 39.58) at 1 year of injection and 53.01% (95% confidence interval: 40.69, 65.09) at 5 years. In developing/transitional countries post-1995, mean fitted HCV prevalence was 59.13% (95% confidence interval: 30.39, 82.74) at 1 year of injection. In 10 incidence studies, median time at risk was 5.29 years and median cumulative HCV incidence was 20.69%. Mean fitted cumulative incidence was 27.63% (95% confidence interval: 16.92, 41.70) at 1 year of drug injection. The authors concluded that time to HCV infection in developed countries has lengthened. More rapid onset of HCV infection in drug injectors in developing/transitional countries resembles an earlier era of the HCV epidemic in other regions.

Figure 1.

Hepatitis C virus (HCV) prevalence in relation to time at risk (number of years since onset of drug injection), with fitted regression lines (72 studies and 293 categories of time at risk), HCV Synthesis Project, 1989–2006. Data points (circles): reported HCV prevalence for midpoints of the time-at-risk categories; solid line: model-predicted prevalence in relation to time since onset of drug injecting for studies in developed countries after 1995; dashed line: predicted prevalence for developed countries before 1995; dotted line: predicted prevalence for developing/transitional countries. Initial HCV prevalence cannot be interpreted as prevalence at onset of drug injecting because, according to the definition of the HCV Synthesis Project sample, from which the study data were drawn, there were no subjects for whom time at risk = 0.