Methods and indicators to validate country reductions in incidence of hepatitis C virus infection to elimination levels set by WHO

Abstract

One of the main goals of the 2016 Global Health Sector Strategy on viral hepatitis is the elimination of hepatitis C virus (HCV) as a public health problem by 2030, defined as an 80% reduction in incidence and 65% reduction in mortality relative to 2015. Although monitoring HCV incidence is key to validating HCV elimination, use of the gold-standard method, which involves prospective HCV retesting of people at risk, can be prohibitively resource-intensive. Additionally, few countries collected quality data in 2015 to enable an 80% decrease by 2030 to be calculated. Here, we first review different methods of monitoring HCV incidence and discuss their resource implications and applicability to various populations. Second, using mathematical models developed for various global settings, we assess whether trends in HCV chronic prevalence or HCV antibody prevalence or scale-up levels for HCV testing, treatment, and preventative interventions can be used as reliable alternative indicators to validate the HCV incidence target. Third, we discuss the advantages and disadvantages of an absolute HCV incidence target and suggest a suitable threshold. Finally, we propose three options that countries can use to validate the HCV incidence target, depending on the available surveillance infrastructure.

Figure 1a:

Correlation between relative decrease in chronic HCV prevalence and HCV incidence over the course of the HCV elimination initiative for different scale-up levels in HCV treatment without concurrent scale-up in HCV preventative interventions “Gen pop” denotes results from a model of HCV transmission in the general population; PWID denotes results from a model of HCV transmission among PWID

Figure 1b:

Estimated decrease (%) in chronic HCV prevalence when an 80 or 90% decrease in HCV incidence is achieved from scaling-up HCV treatment with or without the concurrent scale-up of HCV preventative interventions. Overall estimates reflect the median and interquartile range of the individual point estimates. GP denotes results from a model of HCV transmission in the general population; PWID denotes results from a model of HCV transmission among PWID; and MSM denotes results from a model of HCV transmission among MSM. In the scenarios including preventative interventions, the level of scale-up is given in Supplementary Table 1.

Figure 2:

Proposed process to validate the hepatitis C virus (HCV) incidence target *If a high-risk population (e.g., people who inject drugs) contributes ≥20% of ongoing incident HCV infections, then it should definitely be monitored because reaching an 80% decrease in country-level incidence would be impossible without decreasing incidence in that group. However, even if a high-risk population contributes ≥10% and <20%, then it should still probably be monitored because decreasing incidence in that group could still be important for reaching the HCV incidence target.