Department of Mathematics and Statistics, University of Guelph, Canada
Background: Despite the availability of highly effective direct-acting antiviral agents (DAA), chronic hepatitis C (CHC) continues to pose a major public health threat worldwide, as the majority of those infected are asymptomatic. The development of effective and tailored strategies to ensure equitable access to CHC care requires an understanding of trends in the geographic and demographic distribution of the disease burden in terms of the number of infections and, more importantly, the number of patients who remain undiagnosed. Such evidence can guide strategic planning and allocation of the resources needed to implement programs for eliminating the disease.
Objectives: To estimate the CHC prevalence and undiagnosed proportion in Ontario, Canada, using a mathematical modeling informed by population-level health administrative data.
Methods: We conducted a population-based retrospective analysis of health administrative data for Ontario from 1999 to 2018 to generate CHC drug utilization, the annual incidence of patients with newly diagnosed hepatocellular carcinoma, decompensated cirrhosis and CHC for three birth cohorts: individuals born before 1945, born between 1945 and 1965, and born after 1965. We developed a back-calculation framework to estimate the historical prevalence of CHC for each cohort. We used a Bayesian Markov Chain Monte Carlo algorithm to back-calculate the historical CHC prevalence and the undiagnosed proportion through a calibration process. The algorithm constructs the probability distribution of the historical CHC prevalence and the undiagnosed proportion by comparing the model-generated predictions of the annual number of CHC health events against observed data generated in the retrospective analysis.
Results: In 2018, the prevalence was found to be 0.76% (95% CI: 0.61% - 0.97%) among individuals born before 1945, 1.74% (95% CI: 1.52% - 2.30%) among individuals born between 1945 to 1965, and 0.63% (95% CI: 0.55% - 0.74%) among individuals born after 1965. The mean prevalence estimates across all birth cohorts were 0.91% (95%CI: 0.82%-1.04%). The undiagnosed CHC proportion was 19.71% (95% CI: 13.97% -24.85%) among individuals born before 1945, 15.72% (95% CI: 11.27% - 18.54%) among individuals born between 1945 to 1965, and 42.39% (95% CI: 31.26% - 52.89%) among individuals born after 1965. The undiagnosed proportion estimates across all birth cohorts were 34.28% (95% CI: 26.7%-41.6%).
Conclusions: This is the first study to estimate CHC prevalence and undiagnosed proportion in Canada after the introduction of new DAA treatment using provincial health administrative data. Our findings can provide evidence to guide decision-making on CHC screening strategies to reach undiagnosed individuals and help meeting the elimination target.
