This study states that the methods of data collection and inclusion criteria for patients with chronic hepatitis C in our cohort have been described [5]. The cohort is based on electronic health records (EHR) of adults who received services at the following health systems since 2006: Geisinger Health System (Pennsylvania); Henry Ford Health System (Michigan); Kaiser Permanente–Northwest (Oregon); and Kaiser Permanente–Honolulu (Hawaii). Patients were classified with hepatitis C based on positive HCV RNA tests and International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes. EHR data were supplemented with record reviews by trained abstractors to collect additional demographic and clinical information. The study period for this analysis commenced on 1 January 2011 and ended on 31 December 2017 or date of death, whichever came first. For patients who entered care after 1 January 2011, follow-up began at the date of first clinical service. Patients who died before 1 January 2011 and those with hepatitis B virus or human immunodeficiency virus infection were excluded from the analysis. As previously, we examined causes of death from death certificates of HCV-infected decedents and the frequency that hepatitis C was documented as an underlying.

Reference link- https://academic.oup.com/cid/article/73/5/891/6131867