The Impact of New Direct-Acting Antiviral Therapy on the Prevalence and Undiagnosed Proportion of Chronic Hepatitis C Infection in Alberta: A Model-Based Analysis.

Background: Understanding the impact of wider access to treatment on chronic hepatitis C (CHC) prevalence and the undiagnosed CHC proportion is important to achieving the World Health Organization's 2030 elimination targets. This research aimed to: (1) estimate the CHC prevalence and undiagnosed rates in Alberta, Canada; and (2) explore the impact of new direct-acting antiviral therapy on these rates since its introduction in 2014.

Methods: This study adopted a two-step approach to estimate CHC prevalence and undiagnosed rates. This involved a population-based retrospective analysis of health administrative data for Alberta from 2002 to 2018 to generate CHC-related events for three birth cohorts: individuals born before 1945, individuals born between 1945 and 1965, and individuals born after 1965. A back-calculation method was employed to obtain historical prevalence and incidence estimates.

Results: After the introduction of direct-acting antiviral treatment in 2014, the mean prevalence of CHC over all the birth cohorts fell by approximately 6.5% from 1.23% (95% CI: 0.97%-1.5%) to 1.15% (95% CI: 0.91%-1.45%) between 2015 and 2018. Similar trends were estimated for the 1945-1965 and the >1965 birth cohorts over the same period. Likewise, the mean proportion of undiagnosed CHC infections over all the birth cohorts fell by approximately 8.25% from 39.36% (95% CI: 30.08%-48.48%) to 36.36% (95% CI: 27.49%-45.31%) over the same period. A similar trend was experienced in all three birth cohorts.

Conclusions: This is the first study to estimate CHC prevalence and undiagnosed proportions in Alberta using provincial health administrative data. These results could provide vital evidence to guide decisions about current and future hepatitis C virus strategies and help achieve the World Health Organization goal of eliminating hepatitis C in Canada by 2030.