Diagnosis and treatment coverage among hepatitis C infections in Denmark, 2022: a capture-recapture study using national registers

BACKGROUND: Following the introduction of direct-acting antivirals (DAAs), elimination of hepatitis C virus (HCV) became a target of the World Health Organisation (WHO) in 2016. Denmark had a HCV prevalence of 0.21% in 2016, and in 2018, unrestricted access to DAAs was introduced together with intensified testing strategies. AIM: To estimate adult HCV diagnostic and treatment coverage in Denmark by the end of 2022. METHODS: Four national HCV source registers (laboratory reports, surveillance notifications, treatment database and hospital diagnoses) were merged. Capture-recapture analysis was used to estimate diagnosed individuals not identified in the registers, and estimates were adjusted for treated patients. The undiagnosed population was estimated using HCV testing data among high-risk individuals recorded in the Register for Treatment of Drug Use and compared with Danish studies on the diagnosed fraction of newly detected HCV cases. RESULTS: Across the four registers, 1,649 valid records of HCV-infected adults alive and resident in Denmark were identified. Capture-recapture analysis estimated a total of 1,700 (95% CI: 1,677-1,739) diagnosed individuals. With an undiagnosed fraction of 22-32%, the total HCV-infected population was estimated at 2,471-2,582 individuals, corresponding to a prevalence of 0.05-0.06% by the end of 2022. Compared to the 2016 baseline 82% had been diagnosed and 77% of diagnosed patients had been treated for HCV. CONCLUSION: HCV prevalence in Denmark has declined substantially, and with ongoing national initiatives to test and treat the remaining HCV patients we are likely to achieve WHO targets of diagnostic coverage and treatment before 2030.