our analysis. This coverage bias would result in an under-estimate of the population proportion of PWID and an over-estimate of disease rates. A third limitation is the degree of heterogeneity among surveys. Although all surveys are population-based, the sampling methods, age range, and question wording vary across surveys. We used random-effects models to account for variance beyond sampling errors. As noted, the rates among those aged 13–24 years and 50 years or older may be under-estimates given that the meta-analysis was limited to those aged 18–64 years. Other limitations are inherent from the surveillance data used in the rate calculations [5]. The HCV infection data are subject to the limitations of NHANES [4].
