Using Surveillance Data to Develop a Hepatitis C Care Cascade in New York City

BACKGROUND: Approximately 146,500 New York City (NYC) residents have hepatitis C virus (HCV) infection‎. Health departments monitor access to treatment for people with HIV infection by applying validated definitions of infection, linked to care, on treatment, and viral suppression to laboratory-based surveillance data, generating a “care cascade.” HCV epidemics have not been similarly monitored because there are no validated definitions applicable to data routinely reported to health departments. 

METHODS: Laboratories electronically report to the NYC Health Department all positive HCV antibody, RNA, and genotype results and, since July 2014, negative RNA results for NYC residents. We developed definitions for linkage to care, “on treatment,” and sustained virologic response (i.e., cure) that relied only on these laboratory data. Linkage to care was defined as one positive RNA or genotype result at least one day after and within six months of an initial antibody positive result. “On treatment” was defined as a most recent negative RNA, preceded by at least one positive RNA result. Cure was defined relative to the date of an individual’s first negative RNA or low-positive RNA (below <1000 IU/mL): an individual must have had at least one positive RNA before this date and two negative RNAs and no positive RNA after this date. We used clinical records for 998 patients from a Health Department project to validate these definitions. We then applied the definitions to surveillance data reported from January 2011-October 2015. 

RESULTS: When compared with clinical records, the “on treatment” definition had a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 90.6%, 90.1%, 85.0% and 93.9%, respectively. The cure definition had a sensitivity, specificity, PPV, and NPV of 90.0%, 98.0%, 62.8%, and 99.7%, respectively. When applied to surveillance data from January 2011-October 2015, the linkage to care definition showed that 43% were linked within 6 months, 5% had an RNA test ordered the same day as an antibody test, 16% were linked after six months, and 36% were not linked. Of 33,400 cases with a positive RNA reported from September 2014-August 2015, 10,332 (30.9%) were currently on HCV treatment and 5,277 (15.8%) were deemed cured.

CONCLUSIONS: Routine HCV surveillance data can be used to estimate the proportion of people on treatment and cured. We estimate that most New Yorkers recently diagnosed with HCV have not been treated and cured, suggesting that tens of thousands remain at high risk of HCV-related illness and death.