Time from migration to diagnosis and the proportion presenting late among diagnosed cases of chronic hepatitis B in Norway, 2008 to 2022.

Background: Early diagnosis of chronic hepatitis B virus (CHB) prevents onward transmission and liver disease progression. In Norway, CHB infections are concentrated among migrants from countries with a high CHB prevalence.

Objectives: To calculate time from migration to diagnosis and proportion presenting late (a hospital consultation for end-stage liver disease within 24 months after CHB diagnosis) among diagnosed cases of CHB in Norway from 2008-2022.

Method: We analysed linked national registry data and described each outcome by year, age, sex, region of residence and country of birth. We explored factors associated with time from migration to diagnosis in accelerated failure time models and presented adjusted time ratios (aTR) with 95% confidence intervals (CI).

Results: Among 10,542 cases of CHB, 273 (2.6%) presented late, with a higher proportion in older age groups (≥60 years: 11%). The median time from migration to diagnosis among 3,665 cases who migrated from 2008 onwards was 1.1 years (interquartile range: 0.3-3.1). Compared to cases from high-prevalence countries with a high proportion of refugees or asylum seekers to Norway, cases born in other high-prevalence countries (aTR: 1.37, 95% CI: 1.26-1.50) or low-prevalence countries (aTR: 1.66, 95% CI: 1.49-1.89) had a longer time from migration to diagnosis.

Conclusion: Among persons diagnosed with CHB in Norway, 2-3% present with severe liver disease within 2 years of CHB diagnosis. Initiatives to improve testing strategies could focus on migrants from high-prevalence countries arriving for reasons other than refuge or who arrived several years ago but have not yet been tested.