Existing data on HCV sero-prevalence in these patients in Hong Kong is however fragmented especially in non-hospitalized persons. From the year 2014 surveillance report prepared by Department of Health (DH), anti-HCV prevalence rate among PWID under DH's methadone clinics was 46.2%. Two major issues remain in view of the high seroprevalence rate in this subgroup. Firstly, HCV RNA positivity was not reported and it is unknown whether these patients are still chronically infected. Many of patients are not directed to subsequent confirmatory tests and if they are chronically infected, they need to be linked to care. Secondly, data does not exist for these high-risk populations in Hong Kong. These subjects belong to high-risk group of harbouring undiagnosed chronic HCV and thus should be tested and linked to care.

Traditionally, the first step in screening for HCV utilizes enzyme immunoassay for the antibody against HCV. Fortunately, newer rapid diagnostic tests (RDT) can be used as a tool to screen subjects by providing point-of-care diagnosis on site. For instance, the OraQuick® HCV test (OraSure Technologies, Inc) is FDA-approved and CLIA-waived, with more than 98% sensitivity and specificity for qualitative detection of anti-HCV antibody in finger stick or venepuncture whole blood. As the volume of blood required is much smaller, subjects only need a finger stick for testing and results will be available within 20-40min. Subjects having positive results from RDT will proceed with venepuncture for collection of whole blood which will be sent back to our laboratory for confirmatory testing of anti-HCV antibody and HCV RNA.

Upon confirmation of diagnosis, subjects should be linked to care for further management. Ideally, all patients with chronic HCV should be treated regardless of severity of liver disease unless liver decompensation has developed necessitating liver transplantation before treatment or limited lifespan is expected even with DAA treatment. An integrated linkage-to-care clinic for all patients with newly diagnosed chronic HCV. Patients will be assessed in a timely manner. A dedicated research nurse will provide counselling and education to the patients. The nurse will then arrange on-site liver stiffness measurement with Fibroscan®, as well as phlebotomy for liver function test assessment.

This is a prospective cohort study. The investigators will form an outreach team and conduct visits to the relevant premises. The investigators will perform rapid diagnostic test (RDT) in high-risk populations. The investigators plan to conduct site visits every 4 - 8 weeks. The consent and potential impact of this study will be explained to subjects, followed by obtaining consent and blood taking. Subjects will also be asked to fill in a questionnaire, including information on age, gender, place of birth, ethnic origin, chronic medical illness, prior viral hepatitis infection, history of receiving HCV treatment and risk factors for contracting HCV (e.g. prior transfusion, intravenous drug use, tooth extraction or gum surgery, skin tattooing). Subjects will then have finger stick, which will be used for RDT as a point-of-care HCV screening test. If the RDT result is positive, the subject will then proceed with formal venepuncture for whole blood, which will be tested for confirmatory anti-HCV and HCV RNA (HCV genotype will also be determined for HCV RNA positive samples) in our own laboratory. The investigators will actively contact subjects confirmed with the diagnosis of chronic HCV. The research nurse will contact them to attend the integrated linkage-to-care clinic for counselling, education and risk stratification. During the clinic visits, risk stratification according to the liver status will be done by 1) physical examinations to document the clinical liver status, 2) comprehensive blood investigations including liver function tests, platelet counts and clotting profiles and 3) Fibroscan® to assess the fibrosis status. For institutionalised subjects, the invesrigators will conduct additional site visits for prescription and verification of SVR.