Abstract and Introduction
The hepatitis C virus (HCV) care cascade has been well characterized in the general United States population and other subpopulations since curative medications have been available. However, information is limited on care cascade outcomes in persons experiencing homelessness. The main objective of this study was to map the available evidence on HCV care cascade outcomes in people experiencing homelessness in the U.S. in the era of direct-acting antiviral agents (DAAs). Primary and secondary outcomes included linkage to care (evaluation by a provider that can treat HCV) and sustained virologic response (SVR) or cure. Exploratory outcomes included other cascade data, like treatment initiation, which precedes SVR. PubMed was the primary database accessed for this scoping review. We characterized the HCV care cascade in people experiencing homelessness using sources of evidence published in 2014 onwards that reported the proportions of persons who were linked to care, achieved SVR, and completed other cascade steps. We synthesized our results into a scoping review. The proportion of persons linked to care among chronically infected cohorts with unstable housing ranged from 29.3% to 88.7%. Among those chronically infected, 5%–58.8% were started on DAAs and 5%–50% achieved SVR. In conclusion, these results show that persons experiencing homelessness achieve high rates of linkage to care in non-specialist community-based settings compared to the general U.S. population pre-DAAs. However, DAA initiation was found to be a rate-limiting step along the care cascade, resulting in commensurate low rates of cure.
As the most common blood-borne infection in the United States, hepatitis C virus (HCV) is responsible for significant morbidity and mortality. In 2012, the rising mortality rate associated with HCV surpassed that of sixty other nationally notifiable infectious conditions combined. Many with HCV are asymptomatic, allowing cirrhosis, hepatocellular carcinoma, and other sequelae to develop undetected. Of 2.4 million people in the U.S. currently infected, 50% are unaware.[2,3] Lack of awareness in high-risk communities perpetuates transmission where the opioid epidemic and injection drug use drive incident cases.
Screening is a critical first step in addressing the burden of HCV, with individual- and population-level benefits. Screening is only beneficial as a population health tool, however, if it leads to improved health outcomes. The importance of screening is highlighted by the availability of oral direct-acting antiviral agents (DAAs), making it possible for over 95% of patients to achieve sustained virologic response (SVR) or cure. Before the advent of DAAs, interferon injections were standard of care. These were often associated with intolerable side effects and longer treatment durations, which may have been more prohibitive among individuals experiencing homelessness and those with underlying mental health conditions. In addition to high curative potential, DAAs offer short treatment courses and minimal side effects.
Advancements in diagnosis and treatment have limited impact without comparable progress in linkage to care, a critical intermediate step where focused efforts can lead to more people being cured. The HCV care cascade is a sequence of measurable indicators that patients navigate on the path to cure. Key steps include screening, diagnosis, linkage to care, treatment initiation, and SVR. These indicators also track population health level progress for groups of interest. This cascade has been well characterized in the general U.S. population pre-DAAs (Figure 1) and in subpopulations of persons who inject drugs.[3,4] However, information is limited on cascade outcomes in persons experiencing homelessness in the DAA era, which offers opportunities to close gaps in vulnerable populations.
Treatment cascade for people with chronic HCV infection, adapted from a systematic review published by Yehia et al.3
People experiencing homelessness have a high prevalence of HCV infection. In a national study by Strehlow et al., risk factors for HCV infection among individuals seeking care at Health Care for the Homeless primary care clinics were injection drug use, incarceration, and tattoos. In addition to the high prevalence rate, persons experiencing homelessness encounter many barriers to treatment. Masson et al. stratified these barriers into individual, system, and social-level barriers. Identified barriers on the individual level included comorbid medical and psychiatric conditions as well as misconceptions about HCV. Stigma surrounding homelessness and limited staff advocacy for HCV services presented barriers at the social and system levels, respectively.
The objective of this study is to map the available evidence on HCV care cascade outcomes in persons experiencing homelessness in the U.S. using studies published within PubMed from 2014 onwards, signifying the start of exclusively DAA regimens. This broad objective is best accomplished through scoping review methods. Primary and secondary outcomes include linkage to care and SVR, respectively.